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diff --git a/docs/html/training/basics/firstapp/building-ui.jd b/docs/html/training/basics/firstapp/building-ui.jd new file mode 100644 index 0000000..847163a --- /dev/null +++ b/docs/html/training/basics/firstapp/building-ui.jd @@ -0,0 +1,363 @@ +page.title=Building a Simple User Interface +parent.title=Building Your First App +parent.link=index.html + +trainingnavtop=true +previous.title=Running Your App +previous.link=running-app.html +next.title=Starting Another Activity +next.link=starting-activity.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> + +<ol> + <li><a href="#LinearLayout">Use a Linear Layout</a></li> + <li><a href="#TextInput">Add a Text Input Box</a></li> + <li><a href="#Strings">Add String Resources</a></li> + <li><a href="#Button">Add a Button</a></li> + <li><a href="#Weight">Make the Input Box Fill in the Screen Width</a></li> +</ol> + + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}guide/topics/ui/declaring-layout.html">XML Layouts</a></li> +</ul> + + +</div> +</div> + + + +<p>The graphical user interface for an Android app is built using a hierarchy of {@link +android.view.View} and {@link android.view.ViewGroup} objects. {@link android.view.View} objects are +usually UI widgets such as a button or text field and {@link android.view.ViewGroup} objects are +invisible view containers that define how the child views are laid out, such as in a +grid or a vertical list.</p> + +<p>Android provides an XML vocabulary that corresponds to the subclasses of {@link +android.view.View} and {@link android.view.ViewGroup} so you can define your UI in XML with a +hierarchy of view elements.</p> + + +<div class="sidebox-wrapper"> +<div class="sidebox"> + <h2>Alternative Layouts</h2> + <p>Separating the UI layout into XML files is important for several reasons, +but it's especially important on Android because it allows you to define alternative layouts for +different screen sizes. For example, you can create two versions of a layout and tell +the system to use one on "small" screens and the other on "large" screens. For more information, +see the class about <a +href="{@docRoot}training/supporting-hardware/index.html">Supporting Various Hardware</a>.</p> +</div> +</div> + +<img src="{@docRoot}images/viewgroup.png" alt="" /> +<p class="img-caption"><strong>Figure 1.</strong> Illustration of how {@link +android.view.ViewGroup} objects form branches in the layout and contain {@link +android.view.View} objects.</p> + +<p>In this lesson, you'll create a layout in XML that includes a text input field and a +button. In the following lesson, you'll respond when the button is pressed by sending the +content of the text field to another activity.</p> + + + +<h2 id="LinearLayout">Use a Linear Layout</h2> + +<p>Open the <code>main.xml</code> file from the <code>res/layout/</code> +directory (every new Android project includes this file by default).</p> + +<p class="note"><strong>Note:</strong> In Eclipse, when you open a layout file, you’re first shown +the ADT Layout Editor. This is an editor that helps you build layouts using WYSIWYG tools. For this +lesson, you’re going to work directly with the XML, so click the <em>main.xml</em> tab at +the bottom of the screen to open the XML editor.</p> + +<p>By default, the <code>main.xml</code> file includes a layout with a {@link +android.widget.LinearLayout} root view group and a {@link android.widget.TextView} child view. +You’re going to re-use the {@link android.widget.LinearLayout} in this lesson, but change its +contents and layout orientation.</p> + +<p>First, delete the {@link android.widget.TextView} element and change the value +<a href="{@docRoot}reference/android/widget/LinearLayout.html#attr_android:orientation">{@code +android:orientation}</a> to be <code>"horizontal"</code>. The result looks like this:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" + android:layout_width="fill_parent" + android:layout_height="fill_parent" + android:orientation="horizontal" > +</LinearLayout> +</pre> + +<p>{@link android.widget.LinearLayout} is a view group (a subclass of {@link +android.view.ViewGroup}) that lays out child views in either a vertical or horizontal orientation, +as specified by the <a +href="{@docRoot}reference/android/widget/LinearLayout.html#attr_android:orientation">{@code +android:orientation}</a> attribute. Each child of a {@link android.widget.LinearLayout} appears on +the screen in the order in which it appears in the XML.</p> + +<p>The other two attributes, <a +href="{@docRoot}reference/android/view/View.html#attr_android:layout_width">{@code +android:layout_width}</a> and <a +href="{@docRoot}reference/android/view/View.html#attr_android:layout_height">{@code +android:layout_height}</a>, are required for all views in order to specify their size.</p> + +<p>Because the {@link android.widget.LinearLayout} is the root view in the layout, it should fill +the entire screen area that's +available to the app by setting the width and height to +<code>"fill_parent"</code>.</p> + +<p class="note"><strong>Note:</strong> Beginning with Android 2.2 (API level 8), +<code>"fill_parent"</code> has been renamed <code>"match_parent"</code> to better reflect the +behavior. The reason is that if you set a view to <code>"fill_parent"</code> it does not expand to +fill the remaining space after sibling views are considered, but instead expands to +<em>match</em> the size of the parent view no matter what—it will overlap any sibling +views.</p> + +<p>For more information about layout properties, see the <a +href="{@docRoot}guide/topics/ui/declaring-layout.html">XML Layout</a> guide.</p> + + + +<h2 id="TextInput">Add a Text Input Box</h2> + +<p>To create a user-editable text box, add an {@link android.widget.EditText +<EditText>} element inside the {@link android.widget.LinearLayout <LinearLayout>}. The {@link +android.widget.EditText} class is a subclass of {@link android.view.View} that displays an editable +text box.</p> + +<p>Like every {@link android.view.View} object, you must define certain XML attributes to specify +the {@link android.widget.EditText} object's properties. Here’s how you should declare it +inside the {@link android.widget.LinearLayout <LinearLayout>} element:</p> + +<pre> + <EditText android:id="@+id/edit_message" + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:hint="@string/edit_message" /> +</pre> + + +<div class="sidebox-wrapper"> +<div class="sidebox"> + <h3>About resource objects</h3> + <p>A resource object is simply a unique integer name that's associated with an app resource, +such as a bitmap, layout file, or string.</p> + <p>Every resource has a +corresponding resource object defined in your project's {@code gen/R.java} file. You can use the +object names in the {@code R} class to refer to your resources, such as when you need to specify a +string value for the <a +href="{@docRoot}reference/android/widget/TextView.html#attr_android:hint">{@code android:hint}</a> +attribute. You can also create arbitrary resource IDs that you associate with a view using the <a +href="{@docRoot}reference/android/view/View.html#attr_android:id">{@code android:id}</a> attribute, +which allows you to reference that view from other code.</p> + <p>The SDK tools generate the {@code R.java} each time you compile your app. You should never +modify this file by hand.</p> +</div> +</div> + +<p>About these attributes:</p> + +<dl> +<dt><a href="{@docRoot}reference/android/view/View.html#attr_android:id">{@code android:id}</a></dt> +<dd>This provides a unique identifier for the view, which you can use to reference the object +from your app code, such as to read and manipulate the object (you'll see this in the next +lesson). + +<p>The at-symbol (<code>@</code>) is required when you want to refer to a resource object from +XML, followed by the resource type ({@code id} in this case), then the resource name ({@code +edit_message}). (Other resources can use the same name as long as they are not the same +resource type—for example, the string resource uses the same name.)</p> + +<p>The plus-symbol (<code>+</code>) is needed only when you're defining a resource ID for the +first time. It tells the SDK tools that the resource ID needs to be created. Thus, when the app is +compiled, the SDK tools use the ID value, <code>edit_message</code>, to create a new identifier in +your project's {@code gen/R.java} file that is now assiciated with the {@link +android.widget.EditText} element. Once the resource ID is created, other references to the ID do not +need the plus symbol. See the sidebox for more information about resource objects.</p></dd> + +<dt><a +href="{@docRoot}reference/android/view/View.html#attr_android:layout_width">{@code +android:layout_width}</a> and <a +href="{@docRoot}reference/android/view/View.html#attr_android:layout_height">{@code +android:layout_height}</a></dt> +<dd>Instead of using specific sizes for the width and height, the <code>"wrap_content"</code> value +specifies that the view should be only as big as needed to fit the contents of the view. If you +were to instead use <code>"fill_parent"</code>, then the {@link android.widget.EditText} +element would fill the screen, because it'd match the size of the parent {@link +android.widget.LinearLayout}. For more information, see the <a +href="{@docRoot}guide/topics/ui/declaring-layout.html">XML Layouts</a> guide.</dd> + +<dt><a +href="{@docRoot}reference/android/widget/TextView.html#attr_android:hint">{@code +android:hint}</a></dt> +<dd>This is a default string to display when the text box is empty. Instead of using a hard-coded +string as the value, the value given in this example refers to a string resource. When you add the +{@code +"@string/edit_message"} value, you’ll see a compiler error because there’s no matching string +resource by that name. You'll fix this in the next section by defining the string +resource.</dd> +</dl> + + + +<h2 id="Strings">Add String Resources</h2> + +<p>When you need to add text in the user interface, you should always specify each string of text in +a resource file. String resources allow you to maintain a single location for all string +values, which makes it easier to find and update text. Externalizing the strings also allows you to +localize your app to different languages by providing alternative definitions for each +string.</p> + +<p>By default, your Android project includes a string resource file at +<code>res/values/strings.xml</code>. Open this file, delete the existing <code>"hello"</code> +string, and add one for the +<code>"edit_message"</code> string used by the {@link android.widget.EditText <EditText>} +element.</p> + +<p>While you’re in this file, also add a string for the button you’ll soon add, called +<code>"button_send"</code>.</p> + +<p>The result for <code>strings.xml</code> looks like this:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<resources> + <string name="app_name">My First App</string> + <string name="edit_message">Enter a message</string> + <string name="button_send">Send</string> +</resources> +</pre> + +<p>For more information about using string resources to localize your app for several languages, +see the <a +href="{@docRoot}training/basics/supporting-devices/index.html">Supporting Various Devices</a> +class.</p> + + + + +<h2 id="Button">Add a Button</h2> + +<p>Now add a {@link android.widget.Button <Button>} to the layout, immediately following the +{@link android.widget.EditText <EditText>} element:</p> + +<pre> + <Button + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:text="@string/button_send" /> +</pre> + +<p>The height and width are set to <code>"wrap_content"</code> so the button is only as big as +necessary to fit the button's text.</p> + + + +<h2 id="Weight">Make the Input Box Fill in the Screen Width</h2> + +<p>The layout is currently designed so that both the {@link android.widget.EditText} and {@link +android.widget.Button} widgets are only as big as necessary to fit their content, as shown in +figure 2.</p> + +<img src="{@docRoot}images/training/firstapp/edittext_wrap.png" /> +<p class="img-caption"><strong>Figure 2.</strong> The {@link android.widget.EditText} and {@link +android.widget.Button} widgets have their widths set to +<code>"wrap_content"</code>.</p> + +<p>This works fine for the button, but not as well for the text box, because the user might type +something longer and there's extra space left on the screen. So, it'd be nice to fill that width +using the text box. +{@link android.widget.LinearLayout} enables such a design with the <em>weight</em> property, which +you can specify using the <a +href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#weight">{@code +android:layout_weight}</a> attribute.</p> + +<p>The weight value allows you to specify the amount of remaining space each view should consume, +relative to the amount consumed by sibling views, just like the ingredients in a drink recipe: "2 +parts vodka, 1 part coffee liquer" means two-thirds of the drink is vodka. For example, if you give +one view a weight of 2 and another one a weight of 1, the sum is 3, so the first view gets 2/3 of +the remaining space and the second view gets the rest. If you give a third view a weight of 1, +then the first view now gets 1/2 the remaining space, while the remaining two each get 1/4.</p> + +<p>The default weight for all views is 0, so if you specify any weight value +greater than 0 to only one view, then that view fills whatever space remains after each view is +given the space it requires. So, to fill the remaining space with the {@link +android.widget.EditText} element, give it a weight of 1 and leave the button with no weight.</p> + +<pre> + <EditText + android:layout_weight="1" + ... /> +</pre> + +<p>In order to improve the layout efficiency when you specify the weight, you should change the +width of the {@link android.widget.EditText} to be +zero (0dp). Setting the width to zero improves layout performance because using +<code>"wrap_content"</code> as the width requires the system to calculate a width that is +ultimately irrelevant because the weight value requires another width calculation to fill the +remaining space.</p> +<pre> + <EditText + android:layout_weight="1" + android:layout_width="0dp" + ... /> +</pre> + +<p>Figure 3 +shows the result when you assign all weight to the {@link android.widget.EditText} element.</p> + +<img src="{@docRoot}images/training/firstapp/edittext_gravity.png" /> +<p class="img-caption"><strong>Figure 3.</strong> The {@link android.widget.EditText} widget is +given all the layout weight, so fills the remaining space in the {@link +android.widget.LinearLayout}.</p> + +<p>Here’s how your complete layout file should now look:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" + android:layout_width="fill_parent" + android:layout_height="fill_parent" + android:orientation="horizontal"> + <EditText android:id="@+id/edit_message" + android:layout_weight="1" + android:layout_width="0dp" + android:layout_height="wrap_content" + android:hint="@string/edit_message" /> + <Button android:id="@+id/button_send" + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:text="@string/button_send" /> +</LinearLayout> +</pre> + +<p>This layout is applied by the default {@link android.app.Activity} class +that the SDK tools generated when you created the project, so you can now run the app to see the +results:</p> + +<ul> + <li>In Eclipse, click <strong>Run</strong> from the toolbar.</li> + <li>Or from a command line, change directories to the root of your Android project and +execute: +<pre> +ant debug +adb install bin/MyFirstApp-debug.apk +</pre></li> +</ul> + +<p>Continue to the next lesson to learn how you can respond to button presses, read content +from the text field, start another activity, and more.</p> + + + diff --git a/docs/html/training/basics/firstapp/creating-project.jd b/docs/html/training/basics/firstapp/creating-project.jd new file mode 100644 index 0000000..5a89f2e --- /dev/null +++ b/docs/html/training/basics/firstapp/creating-project.jd @@ -0,0 +1,142 @@ +page.title=Creating an Android Project +parent.title=Building Your First App +parent.link=index.html + +trainingnavtop=true +next.title=Running Your App +next.link=running-app.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> + +<ol> + <li><a href="#Eclipse">Create a Project with Eclipse</a></li> + <li><a href="#CommandLine">Create a Project with Command Line Tools</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}sdk/installing.html">Installing the +SDK</a></li> + <li><a href="{@docRoot}guide/developing/projects/index.html">Managing Projects</a></li> +</ul> + + +</div> +</div> + +<p>An Android project contains all the files that comprise the source code for your Android +app. The Android SDK tools make it easy to start a new Android project with a set of +default project directories and files.</p> + +<p>This lesson +shows how to create a new project either using Eclipse (with the ADT plugin) or using the +SDK tools from a command line.</p> + +<p class="note"><strong>Note:</strong> You should already have the Android SDK installed, and if +you're using Eclipse, you should have installed the <a +href="{@docRoot}sdk/eclipse-adt.html">ADT plugin</a> as well. If you have not installed +these, see <a href="{@docRoot}sdk/installing.html">Installing the Android SDK</a> and return here +when you've completed the installation.</p> + + +<h2 id="Eclipse">Create a Project with Eclipse</h2> + +<div class="figure" style="width:416px"> +<img src="{@docRoot}images/training/firstapp/adt-firstapp-setup.png" alt="" /> +<p class="img-caption"><strong>Figure 1.</strong> The new project wizard in Eclipse.</p> +</div> + +<ol> + <li>In Eclipse, select <strong>File > New > Project</strong>. +The resulting dialog should have a folder labeled <em>Android</em>. (If you don’t see the +<em>Android</em> folder, +then you have not installed the ADT plugin—see <a +href="{@docRoot}sdk/eclipse-adt.html#installing">Installing the ADT Plugin</a>).</li> + <li>Open the <em>Android</em> folder, select <em>Android Project</em> and click +<strong>Next</strong>.</li> + <li>Enter a project name (such as "MyFirstApp") and click <strong>Next</strong>.</li> + <li>Select a build target. This is the platform version against which you will compile your app. +<p>We recommend that you select the latest version possible. You can still build your app to +support older versions, but setting the build target to the latest version allows you to +easily optimize your app for a great user experience on the latest Android-powered devices.</p> +<p>If you don't see any built targets listed, you need to install some using the Android SDK +Manager tool. See <a href="{@docRoot}sdk/installing.html#AddingComponents">step 4 in the +installing guide</a>.</p> +<p>Click <strong>Next</strong>.</p></li> + <li>Specify other app details, such as the: + <ul> + <li><em>Application Name</em>: The app name that appears to the user. Enter "My First +App".</li> + <li><em>Package Name</em>: The package namespace for your app (following the same +rules as packages in the Java programming language). Your package name +must be unique across all packages installed on the Android system. For this reason, it's important +that you use a standard domain-style package name that’s appropriate to your company or +publisher entity. For +your first app, you can use something like "com.example.myapp." However, you cannot publish your +app using the "com.example" namespace.</li> + <li><em>Create Activity</em>: This is the class name for the primary user activity in your +app (an activity represents a single screen in your app). Enter "MyFirstActivity".</li> + <li><em>Minimum SDK</em>: Select <em>4 (Android 1.6)</em>. + <p>Because this version is lower than the build target selected for the app, a warning +appears, but that's alright. You simply need to be sure that you don't use any APIs that require an +<a href="{@docRoot}guide/appendix/api-levels.html">API level</a> greater than the minimum SDK +version without first using some code to verify the device's system version (you'll see this in some +other classes).</p> + </li> + </ul> + <p>Click <strong>Finish</strong>.</p> + </li> +</ol> + +<p>Your Android project is now set up with some default files and you’re ready to begin +building the app. Continue to the <a href="running-app.html">next lesson</a>.</p> + + + +<h2 id="CommandLine">Create a Project with Command Line Tools</h2> + +<p>If you're not using the Eclipse IDE with the ADT plugin, you can instead create your project +using the SDK tools in a command line:</p> + +<ol> + <li>Change directories into the Android SDK’s <code>tools/</code> path.</li> + <li>Execute: +<pre class="no-pretty-print">android list targets</pre> +<p>This prints a list of the available Android platforms that you’ve downloaded for your SDK. Find +the platform against which you want to compile your app. Make a note of the target id. We +recommend that you select the highest version possible. You can still build your app to +support older versions, but setting the build target to the latest version allows you to optimize +your app for the latest devices.</p> +<p>If you don't see any targets listed, you need to +install some using the Android SDK +Manager tool. See <a href="{@docRoot}sdk/installing.html#AddingComponents">step 4 in the +installing guide</a>.</p></li> + <li>Execute: +<pre class="no-pretty-print"> +android create project --target <target-id> --name MyFirstApp \ +--path <path-to-workspace>/MyFirstApp --activity MyFirstActivity \ +--package com.example.myapp +</pre> +<p>Replace <code><target-id></code> with an id from the list of targets (from the previous step) +and replace +<code><path-to-workspace></code> with the location in which you want to save your Android +projects.</p></li> +</ol> + +<p>Your Android project is now set up with several default configurations and you’re ready to begin +building the app. Continue to the <a href="running-app.html">next lesson</a>.</p> + +<p class="note"><strong>Tip:</strong> Add the <code>platform-tools/</code> as well as the +<code>tools/</code> directory to your <code>PATH</code> environment variable.</p> + + + + diff --git a/docs/html/training/basics/firstapp/index.jd b/docs/html/training/basics/firstapp/index.jd new file mode 100644 index 0000000..a95ed8e --- /dev/null +++ b/docs/html/training/basics/firstapp/index.jd @@ -0,0 +1,64 @@ +page.title=Building Your First App + +trainingnavtop=true +startpage=true +next.title=Creating an Android Project +next.link=creating-project.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>Dependencies and prerequisites</h2> + +<ul> + <li>Android 1.6 or higher</li> + <li><a href="http://developer.android.com/sdk/index.html">Android SDK</a></li> +</ul> + +</div> +</div> + +<p>Welcome to Android application development!</p> + +<p>This class teaches you how to build your first Android app. You’ll learn how to create an Android +project and run a debuggable version of the app. You'll also learn some fundamentals of Android app +design, including how to build a simple user interface and handle user input.</p> + +<p>Before you start this class, be sure that you have your development environment set up. You need +to:</p> +<ol> + <li>Download the Android SDK Starter Package.</li> + <li>Install the ADT plugin for Eclipse (if you’ll use the Eclipse IDE).</li> + <li>Download the latest SDK tools and platforms using the SDK Manager.</li> +</ol> + +<p>If you haven't already done this setup, read <a href="{@docRoot}sdk/installing.html">Installing +the SDK</a>. Once you've finished the setup, you're ready to begin this class.</p> + +<p>This class uses a tutorial format that incrementally builds a small Android app in order to teach +you some fundamental concepts about Android development, so it's important that you follow each +step.</p> + +<p><strong><a href="creating-project.html">Start the first lesson ›</a></strong></p> + + +<h2>Lessons</h2> + +<dl> + <dt><b><a href="creating-project.html">Creating an Android Project</a></b></dt> + <dd>Shows how to create a project for an Android app, which includes a set of default +app files.</dd> + + <dt><b><a href="running-app.html">Running Your Application</a></b></dt> + <dd>Shows how to run your app on an Android-powered device or the Android +emulator.</dd> + + <dt><b><a href="building-ui.html">Building a Simple User Interface</a></b></dt> + <dd>Shows how to create a new user interface using an XML file.</dd> + + <dt><b><a href="starting-activity.html">Starting Another Activity</a></b></dt> + <dd>Shows how to respond to a button press, start another activity, send it some +data, then receive the data in the subsequent activity.</dd> +</dl> diff --git a/docs/html/training/basics/firstapp/running-app.jd b/docs/html/training/basics/firstapp/running-app.jd new file mode 100644 index 0000000..2398fa0 --- /dev/null +++ b/docs/html/training/basics/firstapp/running-app.jd @@ -0,0 +1,178 @@ +page.title=Running Your App +parent.title=Building Your First App +parent.link=index.html + +trainingnavtop=true +previous.title=Creating a Project +previous.link=creating-project.html +next.title=Building a Simple User Interface +next.link=building-ui.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> + +<ol> + <li><a href="#RealDevice">Run on a Real Device</a></li> + <li><a href="#Emulator">Run on the Emulator</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/developing/device.html">Using Hardware Devices</a></li> + <li><a href="{@docRoot}guide/developing/devices/index.html">Managing Virtual Devices</a></li> + <li><a href="{@docRoot}guide/developing/projects/index.html">Managing Projects</a></li> +</ul> + + +</div> +</div> + + +<p>If you followed the <a href="{@docRoot}creating-project.html">previous lesson</a> to create an +Android project, it includes a default set of "Hello World" source files that allow you to +run the app right away.</p> + +<p>How you run your app depends on two things: whether you have a real Android-powered device and +whether you’re using Eclipse. This lesson shows you how to install and run your app on a +real device and on the Android emulator, and in both cases with either Eclipse or the command line +tools.</p> + +<p>Before you run your app, you should be aware of a few directories and files in the Android +project:</p> + +<dl> + <dt><code>AndroidManifest.xml</code></dt> + <dd>This manifest file describes the fundamental characteristics of the app and defines each of +its components. You'll learn about various declarations in this file as you read more training +classes.</dd> + <dt><code>src/</code></dt> + <dd>Directory for your app's main source files. By default, it includes an {@link +android.app.Activity} class that runs when your app is launched using the app icon.</dd> + <dt><code>res/</code></dt> + <dd>Contains several sub-directories for app resources. Here are just a few: + <dl style="margin-top:1em"> + <dt><code>drawable-hdpi/</code></dt> + <dd>Directory for drawable objects (such as bitmaps) that are designed for high-density +(hdpi) screens. Other drawable directories contain assets designed for other screen densities.</dd> + <dt><code>layout/</code></dt> + <dd>Directory for files that define your app's user interface.</dd> + <dt><code>values/</code></dt> + <dd>Directory for other various XML files that contain a collection of resources, such as +string and color definitions.</dd> + </dl> + </dd> +</dl> + +<p>When you build and run the default Android project, the default {@link android.app.Activity} +class in the <code>src/</code> directory starts and loads a layout file from the +<code>layout/</code> directory, which includes a "Hello World" message. Not real exciting, but it's +important that you understand how to build and run your app before adding real functionality to +the app.</p> + + + +<h2 id="RealDevice">Run on a Real Device</h2> + +<p>Whether you’re using Eclipse or the command line, you need to:</p> + +<ol> + <li>Plug in your Android-powered device to your machine with a USB cable. +If you’re developing on Windows, you might need to install the appropriate USB driver for your +device. For help installing drivers, see the <a href=”{@docRoot}sdk/oem-usb.html”>OEM USB +Drivers</a> document.</li> + <li>Ensure that <strong>USB debugging</strong> is enabled in the device Settings (open Settings +and navitage to <strong>Applications > Development</strong> on most devices, or select +<strong>Developer options</strong> on Android 4.0 and higher).</li> +</ol> + +<p>To run the app from Eclipse, open one of your project's files and click +<strong>Run</strong> from the toolbar. Eclipse installs the app on your connected device and starts +it.</p> + + +<p>Or to run your app from a command line:</p> + +<ol> + <li>Change directories to the root of your Android project and execute: +<pre class="no-pretty-print">ant debug</pre></li> + <li>Make sure the Android SDK <code>platform-tools/</code> directory is included in your +<code>PATH</code> environment variable, then execute: +<pre class="no-pretty-print">adb install bin/MyFirstApp-debug.apk</pre></li> + <li>On your device, locate <em>MyFirstActivity</em> and open it.</li> +</ol> + +<p>To start adding stuff to the app, continue to the <a href="building-ui.html">next +lesson</a>.</p> + + + +<h2 id="Emulator">Run on the Emulator</h2> + +<p>Whether you’re using Eclipse or the command line, you need to first create an <a +href="{@docRoot}guide/developing/devices/index.html">Android Virtual +Device</a> (AVD). An AVD is a +device configuration for the Android emulator that allows you to model +different device configurations.</p> + +<div class="figure" style="width:457px"> + <img src="{@docRoot}images/screens_support/avds-config.png" alt="" /> + <p class="img-caption"><strong>Figure 1.</strong> The AVD Manager showing a few virtual +devices.</p> +</div> + +<p>To create an AVD:</p> +<ol> + <li>Launch the Android Virtual Device Manager: + <ol type="a"> + <li>In Eclipse, select <strong>Window > AVD Manager</strong>, or click the <em>AVD +Manager</em> icon in the Eclipse toolbar.</li> + <li>From the command line, change directories to <code><sdk>/tools/</code> and execute: +<pre class="no-pretty-print">./android avd</pre></li> + </ol> + </li> + <li>In the <em>Android Virtual Device Device Manager</em> panel, click <strong>New</strong>.</li> + <li>Fill in the details for the AVD. +Give it a name, a platform target, an SD card size, and a skin (HVGA is default).</li> + <li>Click <strong>Create AVD</strong>.</li> + <li>Select the new AVD from the <em>Android Virtual Device Manager</em> and click +<strong>Start</strong>.</li> + <li>After the emulator boots up, unlock the emulator screen.</li> +</ol> + +<p>To run the app from Eclipse, open one of your project's files and click +<strong>Run</strong> from the toolbar. Eclipse installs the app on your AVD and starts it.</p> + + +<p>Or to run your app from the command line:</p> + +<ol> + <li>Change directories to the root of your Android project and execute: +<pre class="no-pretty-print">ant debug</pre></li> + <li>Make sure the Android SDK <code>platform-tools/</code> directory is included in your +<code>PATH</code> environment +variable, then execute: +<pre class="no-pretty-print">adb install bin/MyFirstApp-debug.apk</pre></li> + <li>On the emulator, locate <em>MyFirstActivity</em> and open it.</li> +</ol> + + +<p>To start adding stuff to the app, continue to the <a href="building-ui.html">next +lesson</a>.</p> + + + + + + + + + + + diff --git a/docs/html/training/basics/firstapp/starting-activity.jd b/docs/html/training/basics/firstapp/starting-activity.jd new file mode 100644 index 0000000..16a6fd8 --- /dev/null +++ b/docs/html/training/basics/firstapp/starting-activity.jd @@ -0,0 +1,308 @@ +page.title=Starting Another Activity +parent.title=Building Your First App +parent.link=index.html + +trainingnavtop=true +previous.title=Building a Simpler User Interface +previous.link=building-ui.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> + +<ol> + <li><a href="#RespondToButton">Respond to the Send Button</a></li> + <li><a href="#BuildIntent">Build an Intent</a></li> + <li><a href="#StartActivity">Start the Second Activity</a></li> + <li><a href="#CreateActivity">Create the Second Activity</a> + <ol> + <li><a href="#AddToManifest">Add it to the manifest</a></li> + </ol> + </li> + <li><a href="#ReceiveIntent">Receive the Intent</a></li> + <li><a href="#DisplayMessage">Display the Message</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}sdk/installing.html">Installing the +SDK</a></li> +</ul> + + +</div> +</div> + + + +<p>After completing the <a href="building-ui.html">previous lesson</a>, you have an app that +shows an activity (a single screen) with a text box and a button. In this lesson, you’ll add some +code to <code>MyFirstActivity</code> that +starts a new activity when the user selects the Send button.</p> + + +<h2 id="RespondToButton">Respond to the Send Button</h2> + +<p>To respond to the button's on-click event, open the <code>main.xml</code> layout file and add the +<a +href="{@docRoot}reference/android/view/View.html#attr_android:onClick">{@code android:onClick}</a> +attribute to the {@link android.widget.Button <Button>} element:</p> + +<pre> +<Button android:id="@+id/button_send" + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:text="@string/button_send" + android:onClick="sendMessage" /> +</pre> + +<p>The <a +href="{@docRoot}reference/android/view/View.html#attr_android:onClick">{@code +android:onClick}</a> attribute’s value, <code>sendMessage</code>, is the name of a method in your +activity that you want to call when the user selects the button.</p> + +<p>Add the corresponding method inside the <code>MyFirstActivity</code> class:</p> + +<pre> +/** Called when the user selects the Send button */ +public void sendMessage(View view) { + // Do something in response to button +} +</pre> + +<p class="note"><strong>Tip:</strong> In Eclipse, press Ctrl + Shift + O to import missing classes +(Cmd + Shift + O on Mac).</p> + +<p>Note that, in order for the system to match this method to the method name given to <a +href="{@docRoot}reference/android/view/View.html#attr_android:onClick">{@code android:onClick}</a>, +the signature must be exactly as shown. Specifically, the method must:</p> + +<ul> +<li>Be public</li> +<li>Have a void return value</li> +<li>Have a {@link android.view.View} as the only parameter (this will be the {@link +android.view.View} that was clicked)</li> +</ul> + +<p>Next, you’ll fill in this method to read the contents of the text box and deliver that text to +another activity.</p> + + + +<h2 id="BuildIntent">Build an Intent</h2> + +<p>An {@link android.content.Intent} is an object that provides runtime binding between separate +components (such as two activities). The {@link android.content.Intent} represents an +app’s "intent to do something." You can use an {@link android.content.Intent} for a wide +variety of tasks, but most often they’re used to start another activity.</p> + +<p>Inside the {@code sendMessage()} method, create an {@link android.content.Intent} to start +an activity called {@code DisplayMessageActvity}:</p> + +<pre> +Intent intent = new Intent(this, DisplayMessageActivity.class); +</pre> + +<p>The constructor used here takes two parameters:</p> +<ul> + <li>A {@link +android.content.Context} as its first parameter ({@code this} is used because the {@link +android.app.Activity} class is a subclass of {@link android.content.Context}) + <li>The {@link java.lang.Class} of the app component to which the system should deliver +the {@link android.content.Intent} (in this case, the activity that should be started) +</ul> + +<div class="sidebox-wrapper"> +<div class="sidebox"> + <h3>Sending an intent to other apps</h3> + <p>The intent created in this lesson is what's considered an <em>explicit intent</em>, because the +{@link android.content.Intent} +specifies the exact app component to which the intent should be given. However, intents +can also be <em>implicit</em>, in which case the {@link android.content.Intent} does not specify +the desired component, but allows any app installed on the device to respond to the intent +as long as it satisfies the meta-data specifications for the action that's specified in various +{@link android.content.Intent} parameters. For more informations, see the class about <a +href="{@docRoot}training/intents/index.html">Interacting with Other Apps</a>.</p> +</div> +</div> + +<p class="note"><strong>Note:</strong> The reference to {@code DisplayMessageActivity} +will raise an error if you’re using an IDE such as Eclipse because the class doesn’t exist yet. +Ignore the error for now; you’ll create the class soon.</p> + +<p>An intent not only allows you to start another activity, but can carry a bundle of data to the +activity as well. So, use {@link android.app.Activity#findViewById findViewById()} to get the +{@link android.widget.EditText} element and add its message to the intent:</p> + +<pre> +Intent intent = new Intent(this, DisplayMessageActivity.class); +EditText editText = (EditText) findViewById(R.id.edit_message); +String message = editText.getText().toString(); +intent.putExtra(EXTRA_MESSAGE, message); +</pre> + +<p>An {@link android.content.Intent} can carry a collection of various data types as key-value +pairs called <em>extras</em>. The {@link android.content.Intent#putExtra putExtra()} method takes a +string as the key and the value in the second parameter.</p> + +<p>In order for the next activity to query the extra data, you should define your keys using a +public constant. So add the {@code EXTRA_MESSAGE} definition to the top of the {@code +MyFirstActivity} class:</p> + +<pre> +public class MyFirstActivity extends Activity { + public final static String EXTRA_MESSAGE = "com.example.myapp.MESSAGE"; + ... +} +</pre> + +<p>It's generally a good practice to define keys for extras with your app's package name as a prefix +to ensure it's unique, in case your app interacts with other apps.</p> + + +<h2 id="StartActivity">Start the Second Activity</h2> + +<p>To start an activity, you simply need to call {@link android.app.Activity#startActivity +startActivity()} and pass it your {@link android.content.Intent}.</p> + +<p>The system receives this call and starts an instance of the {@link android.app.Activity} +specified by the {@link android.content.Intent}.</p> + +<p>With this method included, the complete {@code sendMessage()} method that's invoked by the Send +button now looks like this:</p> + +<pre> +/** Called when the user selects the Send button */ +public void sendMessage(View view) { + Intent intent = new Intent(this, DisplayMessageActivity.class); + EditText editText = (EditText) findViewById(R.id.edit_message); + String message = editText.getText().toString(); + intent.putExtra(EXTRA_MESSAGE, message); + startActivity(intent); +} +</pre> + +<p>Now you need to create the {@code DisplayMessageActivity} class in order for this to +work.</p> + + + +<h2 id="CreateActivity">Create the Second Activity</h2> + +<p>In your project, create a new class file under the <code>src/<package-name>/</code> +directory called <code>DisplayMessageActivity.java</code>.</p> + +<p class="note"><strong>Tip:</strong> In Eclipse, right-click the package name under the +<code>src/</code> directory and select <strong>New > Class</strong>. +Enter "DisplayMessageActivity" for the name and {@code android.app.Activity} for the superclass.</p> + +<p>Inside the class, add the {@link android.app.Activity#onCreate onCreate()} callback method:</p> + +<pre> +public class DisplayMessageActivity extends Activity { + @Override + public void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + } +} +</pre> + +<p>All subclasses of {@link android.app.Activity} must implement the {@link +android.app.Activity#onCreate onCreate()} method. The system calls this when creating a new +instance of the activity. It is where you must define the activity layout and where you should +initialize essential activity components.</p> + + + +<h3 id="AddToManifest">Add it to the manifest</h3> + +<p>You must declare all activities in your manifest file, <code>AndroidManifest.xml</code>, using an +<a +href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> element.</p> + +<p>Because {@code DisplayMessageActivity} is invoked using an explicit intent, it does not require +any intent filters (such as those you can see in the manifest for <code>MyFirstActivity</code>). So +the declaration for <code>DisplayMessageActivity</code> can be simply one line of code inside the <a +href="{@docRoot}guide/topics/manifest/application-element.html">{@code <application>}</a> +element:</p> + +<pre> +<application ... > + <activity android:name="com.example.myapp.DisplayMessageActivity" /> + ... +</application> +</pre> + +<p>The app is now runnable because the {@link android.content.Intent} in the +first activity now resolves to the {@code DisplayMessageActivity} class. If you run the app now, +pressing the Send button starts the +second activity, but it doesn't show anything yet.</p> + + +<h2 id="ReceiveIntent">Receive the Intent</h2> + +<p>Every {@link android.app.Activity} is invoked by an {@link android.content.Intent}, regardless of +how the user navigated there. You can get the {@link android.content.Intent} that started your +activity by calling {@link android.app.Activity#getIntent()} and the retrieve data contained +within it.</p> + +<p>In the {@code DisplayMessageActivity} class’s {@link android.app.Activity#onCreate onCreate()} +method, get the intent and extract the message delivered by {@code MyFirstActivity}:</p> + +<pre> +Intent intent = getIntent(); +String message = intent.getStringExtra(MyFirstActivity.EXTRA_MESSAGE); +</pre> + + + +<h2 id="DisplayMessage">Display the Message</h2> + +<p>To show the message on the screen, create a {@link android.widget.TextView} widget and set the +text using {@link android.widget.TextView#setText setText()}. Then add the {@link +android.widget.TextView} as the root view of the activity’s layout by passing it to {@link +android.app.Activity#setContentView setContentView()}.</p> + +<p>The complete {@link android.app.Activity#onCreate onCreate()} method for {@code +DisplayMessageActivity} now looks like this:</p> + +<pre> +@Override +public void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + + // Get the message from the intent + Intent intent = getIntent(); + String message = intent.getStringExtra(MyFirstActivity.EXTRA_MESSAGE); + + // Create the text view + TextView textView = new TextView(this); + textView.setTextSize(40); + textView.setText(message); + + setContentView(textView); +} +</pre> + +<p>You can now run the app, type a message in the text box, press Send, and view the message on the +second activity.</p> + +<img src="{@docRoot}images/training/firstapp/firstapp.png" /> +<p class="img-caption"><strong>Figure 1.</strong> Both activities in the final app, running +on Android 4.0. + +<p>That's it, you've built your first Android app!</p> + +<p>To learn more about building Android apps, continue to follow the +basic training classes. The next class is <a +href="{@docRoot}training/activity-lifecycle/index.html">Managing the Activity Lifecycle</a>.</p> + + + + diff --git a/docs/html/training/basics/intents/filters.jd b/docs/html/training/basics/intents/filters.jd new file mode 100644 index 0000000..0090c98 --- /dev/null +++ b/docs/html/training/basics/intents/filters.jd @@ -0,0 +1,244 @@ +page.title=Allowing Other Apps to Start Your Activity +parent.title=Interacting with Other Apps +parent.link=index.html + +trainingnavtop=true +previous.title=Getting a Result from an Activity +previous.link=result.html + +@jd:body + +<div id="tb-wrapper"> + <div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#AddIntentFilter">Add an Intent Filter</a></li> + <li><a href="#HandleIntent">Handle the Intent in Your Activity</a></li> + <li><a href="#ReturnResult">Return a Result</a></li> +</ol> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li> +</ul> + </div> +</div> + +<p>The previous two lessons focused on one side of the story: starting another app's activity from +your app. But if your app can perform an action that might be useful to another app, +your app should be prepared to respond to action requests from other apps. For instance, if you +build a social app that can share messages or photos with the user's friends, it's in your best +interest to support the {@link android.content.Intent#ACTION_SEND} intent so users can initiate a +"share" action from another app and launch your app to perform the action.</p> + +<p>To allow other apps to start your activity, you need to add an <a +href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code <intent-filter>}</a> +element in your manifest file for the corresponding <a +href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> element.</p> + +<p>When your app is installed on a device, the system identifies your intent +filters and adds the information to an internal catalog of intents supported by all installed apps. +When an app calls {@link android.app.Activity#startActivity +startActivity()} or {@link android.app.Activity#startActivityForResult startActivityForResult()}, +with an implicit intent, the system finds which activity (or activities) can respond to the +intent.</p> + + + +<h2 id="AddIntentFilter">Add an Intent Filter</h2> + +<p>In order to properly define which intents your activity can handle, each intent filter you add +should be as specific as possible in terms of the type of action and data the activity +accepts.</p> + +<p>The system may send a given {@link android.content.Intent} to an activity if that activity has +an intent filter fulfills the following criteria of the {@link android.content.Intent} object:</p> + +<dl> + <dt>Action</dt> + <dd>A string naming the action to perform. Usually one of the platform-defined values such +as {@link android.content.Intent#ACTION_SEND} or {@link android.content.Intent#ACTION_VIEW}. + <p>Specify this in your intent filter with the <a +href="{@docRoot}guide/topics/manifest/action-element.html">{@code <action>}</a> element. +The value you specify in this element must be the full string name for the action, instead of the +API constant (see the examples below).</p></dd> + + <dt>Data</dt> + <dd>A description of the data associated with the intent. + <p>Specify this in your intent filter with the <a +href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a> element. Using one +or more attributes in this element, you can specify just the MIME type, just a URI prefix, +just a URI scheme, or a combination of these and others that indicate the data type +accepted.</p> + <p class="note"><strong>Note:</strong> If you don't need to declare specifics about the data +{@link android.net.Uri} (such as when your activity handles to other kind of "extra" data, instead +of a URI), you should specify only the {@code android:mimeType} attribute to declare the type of +data your activity handles, such as {@code text/plain} or {@code image/jpeg}.</p> +</dd> + <dt>Category</dt> + <dd>Provides an additional way to characterize the activity handling the intent, usually related +to the user gesture or location from which it's started. There are several different categories +supported by the system, but most are rarely used. However, all implicit intents are defined with +{@link android.content.Intent#CATEGORY_DEFAULT} by default. + <p>Specify this in your intent filter with the <a +href="{@docRoot}guide/topics/manifest/category-element.html">{@code <category>}</a> +element.</p></dd> +</dl> + +<p>In your intent filter, you can declare which criteria your activity accepts +by declaring each of them with corresponding XML elements nested in the <a +href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code <intent-filter>}</a> +element.</p> + +<p>For example, here's an activity with an intent filter that handles the {@link +android.content.Intent#ACTION_SEND} intent when the data type is either text or an image:</p> + +<pre> +<activity android:name="ShareActivity"> + <intent-filter> + <action android:name="android.intent.action.SEND"/> + <category android:name="android.intent.category.DEFAULT"/> + <data android:mimeType="text/plain"/> + <data android:mimeType="image/*"/> + </intent-filter> +</activity> +</pre> + +<p>Each incoming intent specifies only one action and one data type, but it's OK to declare multiple +instances of the <a href="{@docRoot}guide/topics/manifest/action-element.html">{@code +<action>}</a>, <a href="{@docRoot}guide/topics/manifest/category-element.html">{@code +<category>}</a>, and <a href="{@docRoot}guide/topics/manifest/data-element.html">{@code +<data>}</a> elements in each +<a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code +<intent-filter>}</a>.</p> + +<p>If any two pairs of action and data are mutually exclusive in +their behaviors, you should create separate intent filters to specify which actions are acceptable +when paired with which data types.</p> + +<p>For example, suppose your activity handles both text and images for both the {@link +android.content.Intent#ACTION_SEND} and {@link +android.content.Intent#ACTION_SENDTO} intents. In this case, you must define two separate +intent filters for the two actions because a {@link +android.content.Intent#ACTION_SENDTO} intent must use the data {@link android.net.Uri} to specify +the recipient's address using the {@code send} or {@code sendto} URI scheme. For example:</p> + +<pre> +<activity android:name="ShareActivity"> + <!-- filter for sending text; accepts SENDTO action with sms URI schemes --> + <intent-filter> + <action android:name="android.intent.action.SENDTO"/> + <category android:name="android.intent.category.DEFAULT"/> + <data android:scheme="sms" /> + <data android:scheme="smsto" /> + </intent-filter> + <!-- filter for sending text or images; accepts SEND action and text or image data --> + <intent-filter> + <action android:name="android.intent.action.SEND"/> + <category android:name="android.intent.category.DEFAULT"/> + <data android:mimeType="image/*"/> + <data android:mimeType="text/plain"/> + </intent-filter> +</activity> +</pre> + +<p class="note"><strong>Note:</strong> In order to receive implicit intents, you must include the +{@link android.content.Intent#CATEGORY_DEFAULT} category in the intent filter. The methods {@link +android.app.Activity#startActivity startActivity()} and {@link +android.app.Activity#startActivityForResult startActivityForResult()} treat all intents as if they +contained the {@link android.content.Intent#CATEGORY_DEFAULT} category. If you do not declare it, no +implicit intents will resolve to your activity.</p> + +<p>For more information about sending and receiving {@link android.content.Intent#ACTION_SEND} +intents that perform social sharing behaviors, see the lesson about <a +href="{@docRoot}training/sharing/receive.html">Receiving Content from Other Apps</a>.</p> + + +<h2 id="HandleIntent">Handle the Intent in Your Activity</h2> + +<p>In order to decide what action to take in your activity, you can read the {@link +android.content.Intent} that was used to start it.</p> + +<p>As your activity starts, call {@link android.app.Activity#getIntent()} to retrieve the +{@link android.content.Intent} that started the activity. You can do so at any time during the +lifecycle of the activity, but you should generally do so during early callbacks such as +{@link android.app.Activity#onCreate onCreate()} or {@link android.app.Activity#onStart()}.</p> + +<p>For example:</p> + +<pre> +@Override +protected void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + + setContentView(R.layout.main); + + // Get the intent that started this activity + Intent intent = getIntent(); + Uri data = intent.getData(); + + // Figure out what to do based on the intent type + if (intent.getType().indexOf("image/") != -1) { + // Handle intents with image data ... + } else if (intent.getType().equals("text/plain")) { + // Handle intents with text ... + } +} +</pre> + + +<h2 id="ReturnResult">Return a Result</h2> + +<p>If you want to return a result to the activity that invoked yours, simply call {@link +android.app.Activity#setResult(int,Intent) setResult()} to specify the result code and result {@link +android.content.Intent}. When your operation is done and the user should return to the original +activity, call {@link android.app.Activity#finish()} to close (and destroy) your activity. For +example:</p> + +<pre> +// Create intent to deliver some kind of result data +Intent result = new Intent("com.example.RESULT_ACTION", Uri.parse("content://result_uri"); +setResult(Activity.RESULT_OK, result); +finish(); +</pre> + +<p>You must always specify a result code with the result. Generally, it's either {@link +android.app.Activity#RESULT_OK} or {@link android.app.Activity#RESULT_CANCELED}. You can then +provide additional data with an {@link android.content.Intent}, as necessary.</p> + +<p class="note"><strong>Note:</strong> The result is set to {@link +android.app.Activity#RESULT_CANCELED} by default. So, if the user presses the <em>Back</em> +button before completing the action and before you set the result, the original activity receives +the "canceled" result.</p> + +<p>If you simply need to return an integer that indicates one of several result options, you can set +the result code to any value higher than 0. If you use the result code to deliver an integer and you +have no need to include the {@link android.content.Intent}, you can call {@link +android.app.Activity#setResult(int) setResult()} and pass only a result code. For example:</p> + +<pre> +setResult(RESULT_COLOR_RED); +finish(); +</pre> + +<p>In this case, there might be only a handful of possible results, so the result code is a locally +defined integer (greater than 0). This works well when you're returning a result to an activity +in your own app, because the activity that receives the result can reference the public +constant to determine the value of the result code.</p> + +<p class="note"><strong>Note:</strong> There's no need to check whether your activity was started +with {@link +android.app.Activity#startActivity startActivity()} or {@link +android.app.Activity#startActivityForResult startActivityForResult()}. Simply call {@link +android.app.Activity#setResult(int,Intent) setResult()} if the intent that started your activity +might expect a result. If the originating activity had called {@link +android.app.Activity#startActivityForResult startActivityForResult()}, then the system delivers it +the result you supply to {@link android.app.Activity#setResult(int,Intent) setResult()}; otherwise, +the result is ignored.</p> + + + + + + diff --git a/docs/html/training/basics/intents/index.jd b/docs/html/training/basics/intents/index.jd new file mode 100644 index 0000000..c661d98 --- /dev/null +++ b/docs/html/training/basics/intents/index.jd @@ -0,0 +1,64 @@ +page.title=Interacting with Other Apps + +trainingnavtop=true +startpage=true +next.title=Sending the User to Another App +next.link=sending.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>Dependencies and prerequisites</h2> +<ul> + <li>Basic understanding of the Activity lifecycle (see <a +href="{@docRoot}training/basics/activity-lifecycle/index.html">Managing the Activity +Lifecycle</a>)</li> +</ul> + + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li> + <li><a +href="http://android-developers.blogspot.com/2009/11/integrating-application-with-intents.html"> +Integrating Application with Intents (blog post)</a></li> + <li><a href="{@docRoot}guide/topics/intents/intents-filters.html">Intents and Intent +Filters</a></li> +</ul> + +</div> +</div> + +<p>An Android app typically has several <a +href="{@docRoot}guide/topics/fundamentals/activities.html">activities</a>. Each activity displays a +user interface that allows the user to perform a specific task (such as view a map or take a photo). +To take the user from one activity to another, your app must use an {@link +android.content.Intent} to define your app's "intent" to do something. When you pass an +{@link android.content.Intent} to the system with a method such as {@link +android.app.Activity#startActivity startActivity()}, the system uses the {@link +android.content.Intent} to identify and start the appropriate app component. Using intents even +allows your app to start an activity that is contained in a separate app.</p> + +<p>An {@link android.content.Intent} can be <em>explicit</em> in order to start a specific component +(a specific {@link android.app.Activity} instance) or <em>implicit</em> in order to start any +component that can handle the intended action (such as "capture a photo").</p> + +<p>This class shows you how to use an {@link android.content.Intent} to perform some basic +interactions with other apps, such as start another app, receive a result from that app, and +make your app able to respond to intents from other apps.</p> + +<h2>Lessons</h2> + +<dl> + <dt><b><a href="sending.html">Sending the User to Another App</a></b></dt> + <dd>Shows how you can create implicit intents to launch other apps that can perform an +action.</dd> + <dt><b><a href="result.html">Getting a Result from an Activity</a></b></dt> + <dd>Shows how to start another activity and receive a result from the activity.</dd> + <dt><b><a href="filters.html">Allowing Other Apps to Start Your Activity</a></b></dt> + <dd>Shows how to make activities in your app open for use by other apps by defining +intent filters that declare the implicit intents your app accepts.</dd> +</dl> + diff --git a/docs/html/training/basics/intents/result.jd b/docs/html/training/basics/intents/result.jd new file mode 100644 index 0000000..0086913 --- /dev/null +++ b/docs/html/training/basics/intents/result.jd @@ -0,0 +1,182 @@ +page.title=Getting a Result from an Activity +parent.title=Interacting with Other Apps +parent.link=index.html + +trainingnavtop=true +previous.title=Sending the User to Another App +previous.link=sending.html +next.title=Allowing Other Apps to Start Your Activity +next.link=filters.html + +@jd:body + +<div id="tb-wrapper"> + <div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#StartActivity">Start the Activity</a></li> + <li><a href="#ReceiveResult">Receive the Result</a></li> +</ol> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li> +</ul> + + </div> +</div> + +<p>Starting another activity doesn't have to be one-way. You can also start another activity and +receive a result back. To receive a result, call {@link android.app.Activity#startActivityForResult +startActivityForResult()} (instead of {@link android.app.Activity#startActivity +startActivity()}).</p> + +<p>For example, your app can start a camera app and receive the captured photo as a result. Or, you +might start the People app in order for the user to select a +contact and you'll receive the contact details as a result.</p> + +<p>Of course, the activity that responds must be designed to return a result. When it does, it +sends the result as another {@link android.content.Intent} object. Your activity receives it in +the {@link android.app.Activity#onActivityResult onActivityResult()} callback.</p> + +<p class="note"><strong>Note:</strong> You can use explicit or implicit intents when you call +{@link android.app.Activity#startActivityForResult startActivityForResult()}. When starting one of +your own activities to receive a result, you should use an explicit intent to ensure that you +receive the expected result.</p> + + +<h2 id="StartActivity">Start the Activity</h2> + +<p>There's nothing special about the {@link android.content.Intent} object you use when starting +an activity for a result, but you do need to pass an additional integer argument to the {@link +android.app.Activity#startActivityForResult startActivityForResult()} method.</p> + +<p>The integer argument is a "request code" that identifies your request. When you receive the +result {@link android.content.Intent}, the callback provides the same request code so that your +app can properly identify the result and determine how to handle it.</p> + +<p>For example, here's how to start an activity that allows the user to pick a contact:</p> + +<pre> +static final int PICK_CONTACT_REQUEST = 1; // The request code +... +private void pickContact() { + Intent pickContactIntent = new Intent(Intent.ACTION_PICK, new Uri("content://contacts")); + pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers + startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST); +} +</pre> + + +<h2 id="ReceiveResult">Receive the Result</h2> + +<p>When the user is done with the subsequent activity and returns, the system calls your activity's +{@link android.app.Activity#onActivityResult onActivityResult()} method. This method includes three +arguments:</p> + +<ul> + <li>The request code you passed to {@link +android.app.Activity#startActivityForResult startActivityForResult()}.</li> + <li>A result code specified by the second activity. This is either {@link +android.app.Activity#RESULT_OK} if the operation was successful or {@link +android.app.Activity#RESULT_CANCELED} if the user backed out or the operation failed for some +reason.</li> + <li>An {@link android.content.Intent} that carries the result data.</li> +</ul> + +<p>For example, here's how you can handle the result for the "pick a contact" intent:</p> + +<pre> +@Override +protected void onActivityResult(int requestCode, int resultCode, Intent data) { + // Check which request we're responding to + if (requestCode == PICK_CONTACT_REQUEST) { + // Make sure the request was successful + if (resultCode == RESULT_OK) { + // The user picked a contact. + // The Intent's data Uri identifies which contact was selected. + + // Do something with the contact here (bigger example below) + } + } +} +</pre> + +<p>In this example, the result {@link android.content.Intent} returned by +Android's Contacts or People app provides a content {@link android.net.Uri} that identifies the +contact the user selected.</p> + +<p>In order to successfully handle the result, you must understand what the format of the result +{@link android.content.Intent} will be. Doing so is easy when the activity returning a result is +one of your own activities. Apps included with the Android platform offer their own APIs that +you can count on for specific result data. For instance, the People app (Contacts app on some older +versions) always returns a result with the content URI that identifies the selected contact, and the +Camera app returns a {@link android.graphics.Bitmap} in the {@code "data"} extra (see the class +about <a href="{@docRoot}training/camera/index.html">Capturing Photos</a>).</p> + + +<h4>Bonus: Read the contact data</h4> + +<p>The code above showing how to get a result from the People app doesn't go into +details about how to actually read the data from the result, because it requires more advanced +discussion about <a href="{@docRoot}guide/topics/providers/content-providers.html">content +providers</a>. However, if you're curious, here's some more code that shows how to query the +result data to get the phone number from the selected contact:</p> + +<pre> +@Override +protected void onActivityResult(int requestCode, int resultCode, Intent data) { + // Check which request it is that we're responding to + if (requestCode == PICK_CONTACT_REQUEST) { + // Make sure the request was successful + if (resultCode == RESULT_OK) { + // Get the URI that points to the selected contact + Uri contactUri = data.getData(); + // We only need the NUMBER column, because there will be only one row in the result + String[] projection = {Phone.NUMBER}; + + // Perform the query on the contact to get the NUMBER column + // We don't need a selection or sort order (there's only one result for the given URI) + // CAUTION: The query() method should be called from a separate thread to avoid blocking + // your app's UI thread. (For simplicity of the sample, this code doesn't do that.) + // Consider using {@link android.content.CursorLoader} to perform the query. + Cursor cursor = getContentResolver() + .query(contactUri, projection, null, null, null); + cursor.moveToFirst(); + + // Retrieve the phone number from the NUMBER column + int column = cursor.getColumnIndex(Phone.NUMBER); + String number = cursor.getString(column); + + // Do something with the phone number... + } + } +} +</pre> + +<p class="note"><strong>Note:</strong> Before Android 2.3 (API level 9), performing a query +on the {@link android.provider.ContactsContract.Contacts Contacts Provider} (like the one shown +above) requires that your app declare the {@link +android.Manifest.permission#READ_CONTACTS} permission (see <a +href="{@docRoot}guide/topics/security/security.html">Security and Permissions</a>). However, +beginning with Android 2.3, the Contacts/People app grants your app a temporary +permission to read from the Contacts Provider when it returns you a result. The temporary permission +applies only to the specific contact requested, so you cannot query a contact other than the one +specified by the intent's {@link android.net.Uri}, unless you do declare the {@link +android.Manifest.permission#READ_CONTACTS} permission.</p> + + + + + + + + + + + + + + + diff --git a/docs/html/training/basics/intents/sending.jd b/docs/html/training/basics/intents/sending.jd new file mode 100644 index 0000000..a71c8f9 --- /dev/null +++ b/docs/html/training/basics/intents/sending.jd @@ -0,0 +1,211 @@ +page.title=Sending the User to Another App +parent.title=Interacting with Other Apps +parent.link=index.html + +trainingnavtop=true +next.title=Getting a Result from an Activity +next.link=result.html + +@jd:body + + +<div id="tb-wrapper"> + <div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#Build">Build an Implicit Intent</a></li> + <li><a href="#Verify">Verify There is an App to Receive the Intent</a></li> + <li><a href="#StartActivity">Start an Activity with the Intent</a></li> +</ol> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li> +</ul> + + </div> +</div> + +<p>One of Android's most important features is an app's ability to send the user to another app +based on an "action" it would like to perform. For example, if +your app has the address of a business that you'd like to show on a map, you don't have to build +an activity in your app that shows a map. Instead, you can send a out a request to view the address +using an {@link android.content.Intent}. The Android system then starts an app that's able to view +the address on a map.</p> + +<p>As shown in the first class, <a href="{@docRoot}training/basics/firstapp/index.html">Building +Your First App</a>, you must use intents to navigate between activities in your own app. You +generally do so with an <em>explicit intent</em>, which defines the exact class name of the +component you want to start. However, when you want to have a separate app perform an action, such +as "view a map," you must use an <em>implicit intent</em>.</p> + +<p>This lesson shows you how to create an implicit intent for a particular action, and how to use it +to start an activity that performs the action in another app.</p> + + + +<h2 id="Build">Build an Implicit Intent</h2> + +<p>Implicit intents do not declare the class name of the component to start, but instead declare an +action to perform. The action specifies the thing you want to do, such as <em>view</em>, +<em>edit</em>, <em>send</em>, or <em>get</em> something. Intents often also include data associated +with the action, such as the address you want to view, or the email message you want to send. +Depending on the intent you want to create, the data might be a {@link android.net.Uri}, +one of several other data types, or the intent might not need data at all.</p> + +<p>If your data is a {@link android.net.Uri}, there's a simple {@link +android.content.Intent#Intent(String,Uri) Intent()} constructor you can use define the action and +data.</p> + +<p>For example, here's how to create an intent to initiate a phone call using the {@link +android.net.Uri} data to specify the telephone number:</p> + +<pre> +Uri number = Uri.parse("tel:5551234"); +Intent callIntent = new Intent(Intent.ACTION_DIAL, number); +</pre> + +<p>When your app invokes this intent by calling {@link android.app.Activity#startActivity +startActivity()}, the Phone app initiates a call to the given phone number.</p> + +<p>Here are a couple other intents and their action and {@link android.net.Uri} data +pairs:</p> + +<ul> + <li>View a map: +<pre> +// Map point based on address +Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California"); +// Or map point based on latitude/longitude +// Uri location = Uri.parse("geo:37.422219,-122.08364?z=14"); // z param is zoom level +Intent mapIntent = new Intent(Intent.ACTION_VIEW, location); +</pre> + </li> + <li>View a web page: +<pre> +Uri webpage = Uri.parse("http://www.android.com"); +Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage); +</pre> + </li> +</ul> + +<p>Other kinds of implicit intents require "extra" data that provide different data types, +such as a string. You can add one or more pieces of extra data using the various {@link +android.content.Intent#putExtra(String,String) putExtra()} methods.</p> + +<p>By default, the system determines the appropriate MIME type required by an intent based on the +{@link android.net.Uri} data that's included. If you don't include a {@link android.net.Uri} in the +intent, you should usually use {@link android.content.Intent#setType setType()} to specify the type +of data associated with the intent. Setting the MIME type further specifies which kinds of +activities should receive the intent.</p> + +<p>Here are some more intents that add extra data to specify the desired action:</p> + +<ul> + <li>Send an email with an attachment: +<pre> +Intent emailIntent = new Intent(Intent.ACTION_SEND); +// The intent does not have a URI, so declare the "text/plain" MIME type +emailIntent.setType(HTTP.PLAIN_TEXT_TYPE); +emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[] {"jon@example.com"}); // recipients +emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Email subject"); +emailIntent.putExtra(Intent.EXTRA_TEXT, "Email message text"); +emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("content://path/to/email/attachment"); +// You can also attach multiple items by passing an ArrayList of Uris +</pre> + </li> + <li>Create a calendar event: +<pre> +Intent calendarIntent = new Intent(Intent.ACTION_INSERT, Events.CONTENT_URI); +Calendar beginTime = Calendar.getInstance().set(2012, 0, 19, 7, 30); +Calendar endTime = Calendar.getInstance().set(2012, 0, 19, 10, 30); +calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis()); +calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis()); +calendarIntent.putExtra(Events.TITLE, "Ninja class"); +calendarIntent.putExtra(Events.EVENT_LOCATION, "Secret dojo"); +</pre> +<p class="note"><strong>Note:</strong> This intent for a calendar event is supported only with API +level 14 and higher.</p> + </li> +</ul> + +<p class="note"><strong>Note:</strong> It's important that you define your {@link +android.content.Intent} to be as specific as possible. For example, if you want to display an image +using the {@link android.content.Intent#ACTION_VIEW} intent, you should specify a MIME type of +{@code image/*}. This prevents apps that can "view" other types of data (like a map app) from being +triggered by the intent.</p> + + + +<h2 id="Verify">Verify There is an App to Receive the Intent</h2> + +<p>Although the Android platform guarantees that certain intents will resolve to one of the +built-in apps (such as the Phone, Email, or Calendar app), you should always include a +verification step before invoking an intent.</p> + +<p class="caution"><strong>Caution:</strong> If you invoke an intent and there is no app +available on the device that can handle the intent, your app will crash.</p> + +<p>To verify there is an activity available that can respond to the intent, call {@link +android.content.pm.PackageManager#queryIntentActivities queryIntentActivities()} to get a list +of activities capable of handling your {@link android.content.Intent}. If the returned {@link +java.util.List} is not empty, you can safely use the intent. For example:</p> + +<pre> +PackageManager packageManager = {@link android.content.Context#getPackageManager()}; +List<ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0); +boolean isIntentSafe = activities.size() > 0; +</pre> + +<p>If <code>isIntentSafe</code> is <code>true</code>, then at least one app will respond to +the intent. If it is <code>false</code>, then there aren't any apps to handle the intent.</p> + +<p class="note"><strong>Note:</strong> You should perform this check when your activity first +starts in case you need to disable the feature that uses the intent before the user attempts to use +it. If you know of a specific app that can handle the intent, you can also provide a link for the +user to download the app (see how to <a +href="{@docRoot}guide/publishing/publishing.html#marketintent">link to an app on Google +Play</a>).</p> + + +<h2 id="StartActivity">Start an Activity with the Intent</h2> + +<div class="figure" style="width:200px"> + <img src="{@docRoot}images/training/basics/intents-choice.png" alt="" /> + <p class="img-caption"><strong>Figure 1.</strong> Example of the selection dialog that appears +when more than one app can handle an intent.</p> +</div> + +<p>Once you have created your {@link android.content.Intent} and set the extra info, call {@link +android.app.Activity#startActivity startActivity()} to send it to the system. If the system +identifies more than one activity that can handle the intent, it displays a dialog for the user to +select which app to use, as shown in figure 1. If there is only one activity that handles the +intent, the system immediately starts it.</p> + +<pre> +startActivity(intent); +</pre> + +<p>Here's a complete example that shows how to create an intent to view a map, verify that an +app exists to handle the intent, then start it:</p> + +<pre> +// Build the intent +Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California"); +Intent mapIntent = new Intent(Intent.ACTION_VIEW, location); + +// Verify it resolves +PackageManager packageManager = {@link android.content.Context#getPackageManager()}; +List<ResolveInfo> activities = packageManager.queryIntentActivities(mapIntent, 0); +boolean isIntentSafe = activities.size() > 0; + +// Start an activity if it's safe +if (isIntentSafe) { + startActivity(mapIntent); +} +</pre> + + + + diff --git a/docs/html/training/basics/location/currentlocation.jd b/docs/html/training/basics/location/currentlocation.jd new file mode 100644 index 0000000..4692530 --- /dev/null +++ b/docs/html/training/basics/location/currentlocation.jd @@ -0,0 +1,155 @@ +page.title=Obtaining the Current Location +parent.title=Making Your App Location Aware +parent.link=index.html + +trainingnavtop=true +previous.title=Using the Location Manager +previous.link=locationmanager.html +next.title=Displaying the Location Address +next.link=geocoding.html + + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="currentlocation.html#TaskSetupLocationListener">Set Up the Location Listener</a></li> + <li><a href="currentlocation.html#TaskHandleLocationUpdates">Handle Multiple Sources of Location Updates</a></li> + <li><a href="currentlocation.html#TaskGetLastKnownLocation">Use getLastKnownLocation() Wisely</a></li> + <li><a href="currentlocation.html#TaskTerminateUpdates">Terminate Location Updates</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/topics/location/index.html">Location and Maps</a></li> +</ul> + +<h2>Try it out</h2> + +<div class="download-box"> +<a href="http://developer.android.com/shareables/training/LocationAware.zip" class="button">Download + the sample app</a> +<p class="filename">LocationAware.zip</p> +</div> + +</div> +</div> + +<p>After setting up your application to work with {@link android.location.LocationManager}, you can begin to obtain location updates.</p> + +<h2 id="TaskSetupLocationListener">Set Up the Location Listener</h2> + +<p>The {@link android.location.LocationManager} class exposes a number of methods for applications to receive location updates. In its simplest form, you register an event listener, identify the location manager from which you'd like to receive location updates, and specify the minimum time and distance intervals at which to receive location updates. The {@link android.location.LocationListener#onLocationChanged(android.location.Location) onLocationChanged()} callback will be invoked with the frequency that correlates with time and distance intervals.</p> + +<p> +In the sample code snippet below, the location listener is set up to receive notifications at least every 10 seconds and if the device moves by more than 10 meters. The other callback methods notify the application any status change coming from the location provider. +</p> + +<pre> +private final LocationListener listener = new LocationListener() { + + @Override + public void onLocationChanged(Location location) { + // A new location update is received. Do something useful with it. In this case, + // we're sending the update to a handler which then updates the UI with the new + // location. + Message.obtain(mHandler, + UPDATE_LATLNG, + location.getLatitude() + ", " + + location.getLongitude()).sendToTarget(); + + ... + } + ... +}; + +mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, + 10000, // 10-second interval. + 10, // 10 meters. + listener); +</pre> + +<h2 id="TaskHandleLocationUpdates">Handle Multiple Sources of Location Updates</h2> + +<p>Generally speaking, a location provider with greater accuracy (GPS) requires a longer fix time than one with lower accuracy (network-based). If you want to display location data as quickly as possible and update it as more accurate data becomes available, a common practice is to register a location listener with both GPS and network providers. In the {@link android.location.LocationListener#onLocationChanged(android.location.Location) onLocationChanged()} callback, you'll receive location updates from multiple location providers that may have different timestamps and varying levels of accuracy. You'll need to incorporate logic to disambiguate the location providers and discard updates that are stale and less accurate. The code snippet below demonstrates a sample implementation of this logic.</p> + +<pre> +private static final int TWO_MINUTES = 1000 * 60 * 2; + +/** Determines whether one Location reading is better than the current Location fix + * @param location The new Location that you want to evaluate + * @param currentBestLocation The current Location fix, to which you want to compare the new one + */ +protected boolean isBetterLocation(Location location, Location currentBestLocation) { + if (currentBestLocation == null) { + // A new location is always better than no location + return true; + } + + // Check whether the new location fix is newer or older + long timeDelta = location.getTime() - currentBestLocation.getTime(); + boolean isSignificantlyNewer = timeDelta > TWO_MINUTES; + boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES; + boolean isNewer = timeDelta > 0; + + // If it's been more than two minutes since the current location, use the new location + // because the user has likely moved + if (isSignificantlyNewer) { + return true; + // If the new location is more than two minutes older, it must be worse + } else if (isSignificantlyOlder) { + return false; + } + + // Check whether the new location fix is more or less accurate + int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy()); + boolean isLessAccurate = accuracyDelta > 0; + boolean isMoreAccurate = accuracyDelta < 0; + boolean isSignificantlyLessAccurate = accuracyDelta > 200; + + // Check if the old and new location are from the same provider + boolean isFromSameProvider = isSameProvider(location.getProvider(), + currentBestLocation.getProvider()); + + // Determine location quality using a combination of timeliness and accuracy + if (isMoreAccurate) { + return true; + } else if (isNewer && !isLessAccurate) { + return true; + } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) { + return true; + } + return false; +} + +/** Checks whether two providers are the same */ +private boolean isSameProvider(String provider1, String provider2) { + if (provider1 == null) { + return provider2 == null; + } + return provider1.equals(provider2); +} +</pre> + +<h2 id="TaskGetLastKnownLocation">Use getLastKnownLocation() Wisely</h2> + +<p>The setup time for getting a reasonable location fix may not be acceptable for certain applications. You should consider calling the {@link android.location.LocationManager#getLastKnownLocation(java.lang.String) getLastKnownLocation()} method which simply queries Android for the last location update previously received by any location providers. Keep in mind that the returned location may be stale. You should check the timestamp and accuracy of the returned location and decide whether it is useful for your application. If you elect to discard the location update returned from {@link android.location.LocationManager#getLastKnownLocation(java.lang.String) getLastKnownLocation()} and wait for fresh updates from the location provider(s), you should consider displaying an appropriate message before location data is received.</p> + +<h2 id="TaskTerminateUpdates">Terminate Location Updates</h2> + +<p>When you are done with using location data, you should terminate location update to reduce unnecessary consumption of power and network bandwidth. For example, if the user navigates away from an activity where location updates are displayed, you should stop location update by calling {@link android.location.LocationManager#removeUpdates(android.location.LocationListener) removeUpdates()} in {@link android.app.Activity#onStop()}. ({@link android.app.Activity#onStop()} is called when the activity is no longer visible. If you want to learn more about activity lifecycle, read up on the <a href="/training/basic-activity-lifecycle/stopping.html">Starting and Stopping an Activity</a> lesson.</p> + +<pre> +protected void onStop() { + super.onStop(); + mLocationManager.removeUpdates(listener); +} +</pre> + +<p class="note"><strong>Note:</strong> For applications that need to continuously receive and process location updates like a near-real time mapping application, it is best to incorporate the location update logic in a background service and make use of the system notification bar to make the user aware that location data is being used.</p>
\ No newline at end of file diff --git a/docs/html/training/basics/location/geocoding.jd b/docs/html/training/basics/location/geocoding.jd new file mode 100644 index 0000000..6364976 --- /dev/null +++ b/docs/html/training/basics/location/geocoding.jd @@ -0,0 +1,98 @@ +page.title=Displaying the Location Address +parent.title=Making Your App Location Aware +parent.link=index.html + +trainingnavtop=true +previous.title=Obtaining the Current Location +previous.link=currentlocation.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="geocoding.html#TaskReverseGeocoding">Perform Reverse Geocoding</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/topics/location/index.html">Location and Maps</a></li> +</ul> + +<h2>Try it out</h2> + +<div class="download-box"> +<a href="http://developer.android.com/shareables/training/LocationAware.zip" class="button">Download + the sample app</a> +<p class="filename">LocationAware.zip</p> +</div> + +</div> +</div> + +<p>As shown in previous lessons, location updates are received in the form of latitude and longitude coordinates. While this format is useful for calculating distance or displaying a pushpin on a map, the decimal numbers make no sense to most end users. If you need to display a location to user, it is much more preferable to display the address instead.</p> + +<h2 id="TaskReverseGeocoding">Perform Reverse Geocoding</h2> + +<p>Reverse-geocoding is the process of translating latitude longitude coordinates to a human-readable address. The {@link android.location.Geocoder} API is available for this purpose. Note that behind the scene, the API is dependent on a web service. If such service is unavailable on the device, the API will throw a "Service not Available exception" or return an empty list of addresses. A helper method called {@link android.location.Geocoder#isPresent()} was added in Android 2.3 (API level 9) to check for the existence of the service.</p> + +<p>The following code snippet demonstrates the use of the {@link android.location.Geocoder} API to perform reverse-geocoding. Since the {@link android.location.Geocoder#getFromLocation(double, double, int) getFromLocation()} method is synchronous, you should not invoke it from the UI thread, hence an {@link android.os.AsyncTask} is used in the snippet.</p> + +<pre> +private final LocationListener listener = new LocationListener() { + + public void onLocationChanged(Location location) { + // Bypass reverse-geocoding if the Geocoder service is not available on the + // device. The isPresent() convenient method is only available on Gingerbread or above. + if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD && Geocoder.isPresent()) { + // Since the geocoding API is synchronous and may take a while. You don't want to lock + // up the UI thread. Invoking reverse geocoding in an AsyncTask. + (new ReverseGeocodingTask(this)).execute(new Location[] {location}); + } + } + ... +}; + +// AsyncTask encapsulating the reverse-geocoding API. Since the geocoder API is blocked, +// we do not want to invoke it from the UI thread. +private class ReverseGeocodingTask extends AsyncTask<Location, Void, Void> { + Context mContext; + + public ReverseGeocodingTask(Context context) { + super(); + mContext = context; + } + + @Override + protected Void doInBackground(Location... params) { + Geocoder geocoder = new Geocoder(mContext, Locale.getDefault()); + + Location loc = params[0]; + List<Address> addresses = null; + try { + // Call the synchronous getFromLocation() method by passing in the lat/long values. + addresses = geocoder.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1); + } catch (IOException e) { + e.printStackTrace(); + // Update UI field with the exception. + Message.obtain(mHandler, UPDATE_ADDRESS, e.toString()).sendToTarget(); + } + if (addresses != null &s;&s; addresses.size() > 0) { + Address address = addresses.get(0); + // Format the first line of address (if available), city, and country name. + String addressText = String.format("%s, %s, %s", + address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "", + address.getLocality(), + address.getCountryName()); + // Update the UI via a message handler. + Message.obtain(mHandler, UPDATE_ADDRESS, addressText).sendToTarget(); + } + return null; + } +} +</pre>
\ No newline at end of file diff --git a/docs/html/training/basics/location/index.jd b/docs/html/training/basics/location/index.jd new file mode 100644 index 0000000..48cfbc3 --- /dev/null +++ b/docs/html/training/basics/location/index.jd @@ -0,0 +1,51 @@ +page.title=Making Your App Location Aware + +trainingnavtop=true +startpage=true +next.title=Using the Location Manager +next.link=locationmanager.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>Dependencies and prerequisites</h2> + +<ul> + <li>Android 1.0 or higher (2.3+ for the sample app)</li> +</ul> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/topics/location/index.html">Location and Maps</a></li> +</ul> + +<h2>Try it out</h2> + +<div class="download-box"> +<a href="http://developer.android.com/shareables/training/LocationAware.zip" class="button">Download + the sample app</a> +<p class="filename">LocationAware.zip</p> +</div> + +</div> +</div> + +<p>Users bring their mobile devices with them almost everywhere. One of the unique features available to mobile applications is location awareness. Knowing the location and using the information wisely can bring a more contextual experience to your users.</p> + +<p>This class teaches you how to incorporate location based services in your Android application. You'll learn a number of methods to receive location updates and related best practices.</p> + +<h2>Lessons</h2> + +<dl> + <dt><b><a href="locationmanager.html">Using the Location Manager</a></b></dt> + <dd>Learn how to set up your application before it can receive location updates in Android.</dd> + + <dt><b><a href="currentlocation.html">Obtaining the Current Location</a></b></dt> + <dd>Learn how to work with underlying location technologies available on the platform to obtain current location.</dd> + + <dt><b><a href="geocoding.html">Displaying a Location Address</a></b></dt> + <dd>Learn how to translate location coordinates into addresses that are readable to users.</dd> +</dl> diff --git a/docs/html/training/basics/location/locationmanager.jd b/docs/html/training/basics/location/locationmanager.jd new file mode 100644 index 0000000..61abcbd --- /dev/null +++ b/docs/html/training/basics/location/locationmanager.jd @@ -0,0 +1,120 @@ +page.title=Using the Location Manager +parent.title=Making Your App Location Aware +parent.link=index.html + +trainingnavtop=true +next.title=Obtaining the Current Location +next.link=currentlocation.html + +@jd:body + + +<!-- This is the training bar --> +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="locationmanager.html#TaskDeclarePermissions">Declare Proper Permissions in Android Manifest</a></li> + <li><a href="locationmanager.html#TaskGetLocationManagerRef">Get a Reference to LocationManager</a></li> + <li><a href="locationmanager.html#TaskPickLocationProvider">Pick a Location Provider</a></li> + <li><a href="locationmanager.html#TaskVerifyProvider">Verify the Location Provider is Enabled</a></li> +</ol> + +<h2>You should also read</h2> + +<ul> + <li><a href="{@docRoot}guide/topics/location/index.html">Location and Maps</a></li> +</ul> + +<h2>Try it out</h2> + +<div class="download-box"> +<a href="http://developer.android.com/shareables/training/LocationAware.zip" class="button">Download + the sample app</a> +<p class="filename">LocationAware.zip</p> +</div> + +</div> +</div> + +<p>Before your application can begin receiving location updates, it needs to perform some simple steps to set up access. In this lesson, you'll learn what these steps entail.</p> + +<h2 id="TaskDeclarePermissions">Declare Proper Permissions in Android Manifest</h2> + +<p>The first step of setting up location update access is to declare proper permissions in the manifest. If permissions are missing, the application will get a {@link java.lang.SecurityException} at runtime.</p> + +<p>Depending on the {@link android.location.LocationManager} methods used, either {@link android.Manifest.permission#ACCESS_COARSE_LOCATION} or {@link android.Manifest.permission#ACCESS_FINE_LOCATION} permission is needed. For example, you need to declare the {@link android.Manifest.permission#ACCESS_COARSE_LOCATION} permission if your application uses a network-based location provider only. The more accurate GPS requires the {@link android.Manifest.permission#ACCESS_FINE_LOCATION} permission. +Note that declaring the {@link android.Manifest.permission#ACCESS_FINE_LOCATION} permission implies {@link android.Manifest.permission#ACCESS_COARSE_LOCATION} already.</p> + +<p>Also, if a network-based location provider is used in the application, you'll need to declare the internet permission as well.</p> + +<pre> +<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> +<uses-permission android:name="android.permission.INTERNET" /> +</pre> + +<h2 id="TaskGetLocationManagerRef">Get a Reference to LocationManager</h2> + +<p>{@link android.location.LocationManager} is the main class through which your application can access location services on Android. Similar to other system services, a reference can be obtained from calling the {@link android.content.Context#getSystemService(java.lang.String) getSystemService()} method. If your application intends to receive location updates in the foreground (within an {@link android.app.Activity}), you should usually perform this step in the {@link android.app.Activity#onCreate(android.os.Bundle) onCreate()} method.</p> + +<pre> +LocationManager locationManager = + (LocationManager) this.getSystemService(Context.LOCATION_SERVICE); +</pre> + +<h2 id="TaskPickLocationProvider">Pick a Location Provider</h2> + +<p>While not required, most modern Android-powered devices can receive location updates through multiple underlying technologies, which are abstracted to an application as {@link android.location.LocationProvider} objects. Location providers may have different performance characteristics in terms of time-to-fix, accuracy, monetary cost, power consumption, and so on. Generally, a location provider with a greater accuracy, like the GPS, requires a longer fix time than a less accurate one, such as a network-based location provider.</p> + +<p>Depending on your application's use case, you have to choose a specific location provider, or multiple providers, based on similar tradeoffs. For example, a points of interest check-in application would require higher location accuracy than say, a retail store locator where a city level location fix would suffice. The snippet below asks for a provider backed by the GPS.</p> + +<pre> +LocationProvider provider = + locationManager.getProvider(LocationManager.GPS_PROVIDER); +</pre> + +<p>Alternatively, you can provide some input criteria such as accuracy, power requirement, monetary cost, and so on, and let Android decide a closest match location provider. The snippet below asks for a location provider with fine accuracy and no monetary cost. Note that the criteria may not resolve to any providers, in which case a null will be returned. Your application should be prepared to gracefully handle the situation.</p> + +<pre> +// Retrieve a list of location providers that have fine accuracy, no monetary cost, etc +Criteria criteria = new Criteria(); +criteria.setAccuracy(Criteria.ACCURACY_FINE); +criteria.setCostAllowed(false); +... +String providerName = locManager.getBestProvider(criteria, true); + +// If no suitable provider is found, null is returned. +if (providerName != null) { + ... +} +</pre> + +<h2 id="TaskVerifyProvider">Verify the Location Provider is Enabled</h2> + +<p>Some location providers such as the GPS can be disabled in Settings. It is good practice to check whether the desired location provider is currently enabled by calling the {@link android.location.LocationManager#isProviderEnabled(java.lang.String) isProviderEnabled()} method. If the location provider is disabled, you can offer the user an opportunity to enable it in Settings by firing an {@link android.content.Intent} with the {@link android.provider.Settings#ACTION_LOCATION_SOURCE_SETTINGS} action.</p> + +<pre> +@Override +protected void onStart() { + super.onStart(); + + // This verification should be done during onStart() because the system calls + // this method when the user returns to the activity, which ensures the desired + // location provider is enabled each time the activity resumes from the stopped state. + LocationManager locationManager = + (LocationManager) getSystemService(Context.LOCATION_SERVICE); + final boolean gpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER); + + if (!gpsEnabled) { + // Build an alert dialog here that requests that the user enable + // the location services, then when the user clicks the "OK" button, + // call enableLocationSettings() + } +} + +private void enableLocationSettings() { + Intent settingsIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); + startActivity(settingsIntent); +} +</pre> diff --git a/docs/html/training/basics/supporting-devices/index.jd b/docs/html/training/basics/supporting-devices/index.jd new file mode 100644 index 0000000..49ea81d --- /dev/null +++ b/docs/html/training/basics/supporting-devices/index.jd @@ -0,0 +1,49 @@ +page.title=Supporting Different Devices + +trainingnavtop=true +startpage=true +next.title=Supporting Multiple Languages +next.link=languages.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>Dependencies and prerequisites</h2> +<ul> + <li>Android 1.6 or higher</li> +</ul> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}guide/topics/resources/index.html">Application Resources</a></li> + <li><a href="{@docRoot}training/multiscreen/index.html">Designing for Multiple Screens</a></li> +</ul> + + +</div> +</div> + +<p>Android devices come in many shapes and sizes all around the world. With a wide range of device +types, you have an opportunity to reach a huge audience with your app. In order to be as successful +as possible on Android, your app needs to adapt to various device configurations. Some of the +important variations that you should consider include different languages, screen sizes, and +versions of the Android platform.</p> + +<p>This class teaches you how to use basic platform features that leverage alternative +resources and other features so your app can provide an optimized user experience on a +variety of Android-compatible devices, using a single application package (APK).</p> + +<h2>Lessons</h2> + +<dl> + <dt><b><a href="languages.html">Supporting Different Languages</a></b></dt> + <dd>Learn how to support multiple languages with alternative string resources.</dd> + <dt><b><a href="screens.html">Supporting Different Screens</a></b></dt> + <dd>Learn how to optimize the user experience for different screen sizes and densities.</dd> + <dt><b><a href="platforms.html">Supporting Different Platform Versions</a></b></dt> + <dd>Learn how to use APIs available in new versions of Android while continuing to support +older versions of Android.</dd> +</dl> + diff --git a/docs/html/training/basics/supporting-devices/languages.jd b/docs/html/training/basics/supporting-devices/languages.jd new file mode 100644 index 0000000..fcc95c2 --- /dev/null +++ b/docs/html/training/basics/supporting-devices/languages.jd @@ -0,0 +1,134 @@ +page.title=Supporting Different Languages +parent.title=Supporting Different Devices +parent.link=index.html + +trainingnavtop=true +next.title=Supporting Different Screens +next.link=screens.html + +@jd:body + + +<div id="tb-wrapper"> + <div id="tb"> + <h2>This class teaches you to</h2> + <ol> + <li><a href="#CreateDirs">Create Locale Directories and String Files</a></li> + <li><a href="#UseString">Use the String Resources</a></li> + </ol> + <h2>You should also read</h2> + <ul> + <li><a href="{@docRoot}guide/topics/resources/localization.html">Localization</a></li> + </ul> + </div> +</div> + +<p>It’s always a good practice to extract UI strings from your app code and keep them +in an external file. Android makes this easy with a resources directory in each Android +project.</p> + +<p>If you created your project using the Android SDK +Tools (read <a href="{@docRoot}training/basics/firstapp/creating-project.html">Creating an +Android Project</a>), the tools create a <code>res/</code> directory in the top level of +the project. Within this <code>res/</code> directory are subdirectories for various resource +types. There are also a few default files such as <code>res/values/strings.xml</code>, which holds +your string values.</p> + + +<h2 id="CreateDirs">Create Locale Directories and String Files</h2> + +<p>To add support for more languages, create additional <code>values</code> directories inside +<code>res/</code> that include a hyphen and the ISO country code at the end of the +directory name. For example, <code>values-es/</code> is the directory containing simple +resourcess for the Locales with the language code "es". Android loads the appropriate resources +according to the locale settings of the device at run time.</p> + +<p>Once you’ve decided on the languages you will support, create the resource subdirectories and +string resource files. For example:</p> + +<pre class="classic no-pretty-print"> +MyProject/ + res/ + values/ + strings.xml + values-es/ + strings.xml + values-fr/ + strings.xml +</pre> + +<p>Add the string values for each locale into the appropriate file.</p> + +<p>At runtime, the Android system uses the appropriate set of string resources based on the +locale currently set for the user's device.</p> + +<p>For example, the following are some different string resource files for different languages.</p> + + +<p>English (default locale), <code>/values/strings.xml</code>:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<resources> + <string name="title">My Application</string> + <string name="hello_world">Hello World!</string> +</resources> +</pre> + + +<p>Spanish, <code>/values-es/strings.xml</code>:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<resources> + <string name="title">Mi Aplicación</string> + <string name="hello_world">Hola Mundo!</string> +</resources> +</pre> + + +<p>French, <code>/values-fr/strings.xml</code>:</p> + +<pre> +<?xml version="1.0" encoding="utf-8"?> +<resources> + <string name="title">Ma Application</string> + <string name="hello_world">Bonjour tout le Monde!</string> +</resources> +</pre> + + +<h2 id="UseString">Use the String Resources</h2> + +<p>You can reference your string resources in your source code and other XML files using the +resource name defined by the {@code <string>} element's {@code name} attribute.</p> + +<p>In your source code, you can refer to a string resource with the syntax {@code +R.string.<string_name>}. There are a variety of methods that accept a string resource this +way.</p> + +<p>For example:</p> + +<pre> +// Get a string resource from your app's {@link android.content.res.Resources} +String hello = {@link android.content.Context#getResources()}.getString(R.string.hello_world); + +// Or supply a string resource to a method that requires a string +TextView textView = new TextView(this); +textView.setText(R.string.hello_world); +</pre> + +<p>In other XML files, you can refer to a string resource with the syntax {@code +@string/<string_name>} whenever the XML attribute accepts a string value.</p> + +<p>For example:</p> + +<pre> +<TextView + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:text="@string/hello_world" /> +</pre> + + + diff --git a/docs/html/training/basics/supporting-devices/platforms.jd b/docs/html/training/basics/supporting-devices/platforms.jd new file mode 100644 index 0000000..0d4e7d9 --- /dev/null +++ b/docs/html/training/basics/supporting-devices/platforms.jd @@ -0,0 +1,138 @@ +page.title=Supporting Different Platform Versions +parent.title=Supporting Different Devices +parent.link=index.html + +trainingnavtop=true +previous.title=Supporting Different Screens +previous.link=screens.html + +@jd:body + + +<div id="tb-wrapper"> + <div id="tb"> + + <h2>This lesson teaches you to</h2> + <ol> + <li><a href="#sdk-versions">Specify Minimum and Target API Levels</a></li> + <li><a href="#version-codes">Check System Version at Runtime</a></li> + <li><a href="#style-themes">Use Platform Styles and Themes</a></li> + </ol> + + <h2>You should also read</h2> + <ul> + <li><a href="{@docRoot}guide/appendix/api-levels.html">Android API Levels</a></li> + <li><a +href="{@docRoot}sdk/compatibility-library.html">Android Support Library</a></li> + </ul> + </div> +</div> + +<p>While the latest versions of Android often provide great APIs for your app, you should continue +to support older versions of Android until more devices get updated. This +lesson shows you how to take advantage of the latest APIs while continuing to support older +versions as well.</p> + +<p>The dashboard for <a +href="http://developer.android.com/resources/dashboard/platform-versions.html">Platform Versions</a> +is updated regularly to show the distribution of active +devices running each version of Android, based on the number of devices that visit the Google Play +Store. Generally, it’s a good practice to support about 90% of the active devices, while +targeting your app to the latest version.</p> + +<p class="note"><strong>Tip:</strong> In order to provide the best features and +functionality across several Android versions, you should use the <a +href="{@docRoot}sdk/compatibility-library.html">Android Support Library</a> in your app, +which allows you to use several recent platform APIs on older versions.</p> + + + +<h2 id="sdk-versions">Specify Minimum and Target API Levels</h2> + +<p>The <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">AndroidManifest.xml</a> file +describes details about your app and +identifies which versions of Android it supports. Specifically, the <code>minSdkVersion</code> +and <code>targetSdkVersion</code> attributes for the <a +href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">{@code <uses-sdk}</a> element +identify the lowest API level with which your app is compatible and the highest API level against +which you’ve designed and tested your app.</p> + +<p>For example:</p> + +<pre> +<manifest xmlns:android="http://schemas.android.com/apk/res/android" ... > + <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="15" /> + ... +</manifest> +</pre> + +<p>As new versions of Android are released, some style and behaviors may change. +To allow your app to take advantage of these changes and ensure that your app fits the style of +each user's device, you should set the +<a +href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a> +value to match the latest Android version +available.</p> + + + +<h2 id="version-codes">Check System Version at Runtime</h2> + +<p>Android provides a unique code for each platform version in the {@link android.os.Build} +constants class. Use these codes within your app to build conditions that ensure the code that +depends on higher API levels is executed only when those APIs are available on the system.</p> + +<pre> +private void setUpActionBar() { + // Make sure we're running on Honeycomb or higher to use ActionBar APIs + if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) { + ActionBar actionBar = getActionBar(); + actionBar.setDisplayHomeAsUpEnabled(true); + } +} +</pre> + + + +<p class="note"><strong>Note:</strong> When parsing XML resources, Android ignores XML +attributes that aren’t supported by the current device. So you can safely use XML attributes that +are only supported by newer versions without worrying about older versions breaking when they +encounter that code. For example, if you set the +<code>targetSdkVersion="11"</code>, your app includes the {@link android.app.ActionBar} by default +on Android 3.0 and higher. To then add menu items to the action bar, you need to set +<code>android:showAsAction="ifRoom"</code> in your menu resource XML. It's safe to do this +in a cross-version XML file, because the older versions of Android simply ignore the +<code>showAsAction</code> attribute (that is, you <em>do not</em> need a separate +version in <code>res/menu-v11/</code>).</p> + + + +<h2 id="style-themes">Use Platform Styles and Themes</h2> + +<p>Android provides user experience themes that give apps the look and feel of the +underlying operating system. These themes can be applied to your app within the +manifest file. By using these built in styles and themes, your app will +naturally follow the latest look and feel of Android with each new release.</p> + +<p>To make your activity look like a dialog box:</p> + +<pre><activity android:theme="@android:style/Theme.Dialog"></pre> + +<p>To make your activity have a transparent background:</p> + +<pre><activity android:theme="@android:style/Theme.Translucent"></pre> + +<p>To apply your own custom theme defined in <code>/res/values/styles.xml</code>:</p> + +<pre><activity android:theme="@style/CustomTheme"></pre> + +<p>To apply a theme to your entire app (all activities), add the <code>android:theme</code> +attribute +to the <a href="{@docRoot}guide/topics/manifest/application-element.html">{@code +<application>}</a> element:</p> + +<pre><application android:theme="@style/CustomTheme"></pre> + +<p>For more about creating and using themes, read the <a +href="{@docRoot}guide/topics/ui/themes.html">Styles and Themes</a> guide.</p> + diff --git a/docs/html/training/basics/supporting-devices/screens.jd b/docs/html/training/basics/supporting-devices/screens.jd new file mode 100644 index 0000000..8697cd5 --- /dev/null +++ b/docs/html/training/basics/supporting-devices/screens.jd @@ -0,0 +1,180 @@ +page.title=Supporting Different Screens +parent.title=Supporting Different Devices +parent.link=index.html + +trainingnavtop=true +previous.title=Supporting Different Languages +previous.link=languages.html +next.title=Supporting Different Platform Versions +next.link=platforms.html + +@jd:body + +<div id="tb-wrapper"> + <div id="tb"> + + <h2>This lesson teaches you to</h2> + <ol> + <li><a href="#create-layouts">Create Different Layouts</a></li> + <li><a href="#create-bitmaps">Create Different Bitmaps</a></li> + </ol> + + <h2>You should also read</h2> + <ul> + <li><a href="{@docRoot}training/multiscreen/index.html">Designing for Multiple +Screens</a></li> + <li><a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple +Screens</a></li> + <li><a href="{@docRoot}design/style/iconography.html">Iconography design guide</a></li> + </ul> + </div> +</div> + +<p>Android categorizes device screens using two general properties: size and density. You should +expect that your app will be installed on devices with screens that range in both size +and density. As such, you should include some alternative resources that optimize your app’s +appearance for different screen sizes and densities.</p> + +<ul> + <li>There are four generalized sizes: small, normal, large, xlarge</li> + <li>And four generalized densities: low (ldpi), medium (mdpi), high (hdpi), extra high +(xhdpi)</li> +</ul> + +<p>To declare different layouts and bitmaps you'd like to use for different screens, you must place +these alternative resources in separate directories, similar to how you do for different language +strings.</p> + +<p>Also be aware that the screens orientation (landscape or portrait) is considered a variation of +screen size, so many apps should revise the layout to optimize the user experience in each +orientation.</p> + + +<h2 id="create-layouts">Create Different Layouts</h2> + +<p>To optimize your user experience on different screen sizes, you should create a unique layout XML +file for each screen size you want to support. Each layout should be +saved into the appropriate resources directory, named with a <code>-<screen_size></code> +suffix. For example, a unique layout for large screens should be saved under +<code>res/layout-large/</code>.</p> + +<p class="note"><strong>Note:</strong> Android automatically scales your layout in order to +properly fit the screen. Thus, your layouts for different screen sizes don't +need to worry about the absolute size of UI elements but instead focus on the layout structure that +affects the user experience (such as the size or position of important views relative to sibling +views).</p> + +<p>For example, this project includes a default layout and an alternative layout for <em>large</em> +screens:</p> + +<pre class="classic no-pretty-print"> +MyProject/ + res/ + layout/ + main.xml + layout-large/ + main.xml +</pre> + +<p>The file names must be exactly the same, but their contents are different in order to provide +an optimized UI for the corresponding screen size.</p> + +<p>Simply reference the layout file in your app as usual:</p> + +<pre> +@Override + protected void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + setContentView(R.layout.main); +} +</pre> + +<p>The system loads the layout file from the appropriate layout directory based on screen size of +the device on which your app is running. More information about how Android selects the +appropriate resource is available in the <a +href="{@docRoot}guide/topics/resources/providing-resources.html#BestMatch">Providing Resources</a> +guide.</p> + +<p>As another example, here's a project with an alternative layout for landscape orientation:</p> + +<pre class="classic no-pretty-print"> +MyProject/ + res/ + layout/ + main.xml + layout-land/ + main.xml +</pre> + +<p>By default, the <code>layout/main.xml</code> file is used for portrait orientation.</p> + +<p>If you want a provide a special layout for landscape, including while on large screens, then +you need to use both the <code>large</code> and <code>land</code> qualifier:</p> + +<pre class="classic no-pretty-print"> +MyProject/ + res/ + layout/ # default (portrait) + main.xml + layout-land/ # landscape + main.xml + layout-large/ # large (portrait) + main.xml + layout-large-land/ # large landscape + main.xml +</pre> + +<p class="note"><strong>Note:</strong> Android 3.2 and above supports an advanced method of +defining screen sizes that allows you to specify resources for screen sizes based on +the minimum width and height in terms of density-independent pixels. This lesson does not cover +this new technique. For more information, read <a +href="{@docRoot}training/multiscreen/index.html">Designing for Multiple +Screens</a>.</p> + + + +<h2 id="create-bitmaps">Create Different Bitmaps</h2> + +<p>You should always provide bitmap resources that are properly scaled to each of the generalized +density buckets: low, medium, high and extra-high density. This helps you achieve good graphical +quality and performance on all screen densities.</p> + +<p>To generate these images, you should start with your raw resource in vector format and generate +the images for each density using the following size scale:</p> +<ul> +<li>xhdpi: 2.0</li> +<li>hdpi: 1.5</li> +<li>mdpi: 1.0 (baseline)</li> +<li>ldpi: 0.75</li> +</ul> + +<p>This means that if you generate a 200x200 image for xhdpi devices, you should generate the same +resource in 150x150 for hdpi, 100x100 for mdpi, and 75x75 for ldpi devices.</p> + +<p>Then, place the files in the appropriate drawable resource directory:</p> + +<pre class="classic no-pretty-print"> +MyProject/ + res/ + drawable-xhdpi/ + awesomeimage.png + drawable-hdpi/ + awesomeimage.png + drawable-mdpi/ + awesomeimage.png + drawable-ldpi/ + awesomeimage.png +</pre> + +<p>Any time you reference <code>@drawable/awesomeimage</code>, the system selects the +appropriate bitmap based on the screen's density.</p> + +<p class="note"><strong>Note:</strong> Low-density (ldpi) resources aren’t always necessary. When +you provide hdpi assets, the system scales them down by one half to properly fit ldpi +screens.</p> + +<p>For more tips and guidelines about creating icon assets for your app, see the +<a href="{@docRoot}design/style/iconography.html">Iconography design guide</a>.</p> + + + |