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author | Joe Fernandez <joefernandez@google.com> | 2015-05-27 23:42:57 -0700 |
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committer | Joe Fernandez <joefernandez@google.com> | 2015-05-27 23:42:57 -0700 |
commit | 98e01e78c91049bd1639e91120d3d0a841035554 (patch) | |
tree | e6092a04a23874dad6bf64fcb697ab1c2c3c0b6a /docs | |
parent | 6553666f1bb9fef73a7f13ba6bf29c126749d483 (diff) | |
download | frameworks_base-98e01e78c91049bd1639e91120d3d0a841035554.zip frameworks_base-98e01e78c91049bd1639e91120d3d0a841035554.tar.gz frameworks_base-98e01e78c91049bd1639e91120d3d0a841035554.tar.bz2 |
docs: M Preview - removing Data Binding doc file from preview section
Change-Id: Ib056f31e33828702053ba54700e97d67a1554901
Diffstat (limited to 'docs')
-rw-r--r-- | docs/html/preview/data-binding/guide.jd | 908 |
1 files changed, 0 insertions, 908 deletions
diff --git a/docs/html/preview/data-binding/guide.jd b/docs/html/preview/data-binding/guide.jd deleted file mode 100644 index 49b690f..0000000 --- a/docs/html/preview/data-binding/guide.jd +++ /dev/null @@ -1,908 +0,0 @@ -page.title=Data Binding Guide - -@jd:body -<p>Data Binding allows you write declarative layouts and minimize the glue code -that is necessary to bind your application logic and layouts.</p> - - -<h2 id=build_environment>Build Environment</h2> - - -<p><strong>Setting Up Work Environment:</strong></p> - -<p>Data Binding EAP only supports gradle.</p> - -<p>To set up your application, unzip the provided bundle to a location. It has 3 -sections</p> - -<ul> - <li> <em>maven-repo:</em> which keeps the data-binding libraries - <li> <em>samples:</em> Sample applications - <li> <em>databinding.properties:</em> Properties file that can be used to integrate with your app -</ul> - -<p>Add the following section to the project’s build.gradle file (not the module's -build.gradle) and replace <code><BUNDLE_FOLDER> </code>with the absolute path of the bundle that you’ve unzipped in the previous step.</p> - -<pre class=prettyprint> -buildscript { - <strong>def </strong>eapFolder = '<BUNDLE_FOLDER>' -<strong> def </strong>Properties props = <strong>new </strong>Properties() - props.load(<strong>new </strong>FileInputStream(<strong>"</strong>${eapFolder}<strong>/databinding.properties"</strong>)) - props.mavenRepoDir = <strong>"</strong>${eapFolder}<strong>/</strong>${props.mavenRepoName}<strong>" - </strong>ext.config = props - repositories { - jcenter() - maven { - url config.mavenRepoDir - } - } - dependencies { - classpath <strong>"com.android.tools.build:gradle:1.1.3" - </strong>classpath <strong>"com.android.databinding:dataBinder:</strong>${config.snapshotVersion}<strong>" -<em></strong> </em>} -} -allprojects { - repositories { - jcenter() - maven { - url config.mavenRepoDir - } - } -} -</pre> - -<p>Next, add the following lines to the <em>build.gradle</em> -file of each module that will use data-binding. The application module must -have this, even if only its libraries use data binding.</p> - -<pre class=prettyprint> -apply plugin: <strong>'com.android.databinding' -</strong>dependencies { - compile <strong>"com.android.databinding:library:</strong>${config.snapshotVersion}<strong>" -</strong> compile <strong>"com.android.databinding:baseLibrary:</strong>${config.snapshotVersion}<strong>" -</strong> compile <strong>"com.android.databinding:adapters:</strong>${config.snapshotVersion}<strong>" -</strong> provided <strong>"com.android.databinding:annotationprocessor:</strong>${config.snapshotVersion}<strong>" -</strong>} -</pre> - - -<h2 id="data_binding_layout_files">Data Binding Layout Files</h2> - - -<h3 id="writing_expressions">Writing your first data binding expressions:</h3> - -<p>Data-binding layout files are slightly different and start with a root tag of -<strong>layout</strong> followed by a <strong>data</strong> element and a -<strong>view</strong> root element. This view element is what your root would -be in a non-binding layout file.A sample file looks like this:</p> - -<pre class=prettyprint> -<em><?<strong></em>xml version="1.0" encoding="utf-8"<em></strong>?> -</em><<strong>layout xmlns:android="http://schemas.android.com/apk/res/android"</strong>> - <<strong>data</strong>> - <<strong>variable name="user" type="com.example.User"</strong>/> - </<strong>data</strong>> - <<strong>LinearLayout - android:orientation="vertical" - android:layout_width="match_parent" - android:layout_height="match_parent"</strong>> - <<strong>TextView android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@{user.firstName}"</strong>/> - <<strong>TextView android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@{user.lastName}"</strong>/> - </<strong>LinearLayout</strong>> -</<strong>layout</strong>> -</pre> - -<p>The user <strong>variable</strong> within <strong>data</strong> describes a property that may be used within this layout.</p> - -<pre class=prettyprint> -<<strong>variable name="user" type="com.example.User"</strong>/> -</pre> - -<p>Expressions within the layout are written in the attribute properties using the -“<code>@{}</code>” syntax. Here, the TextView’s text is set to the firstName property of user:</p> -<pre class=prettyprint> -<<strong>TextView android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@{user.firstName}"</strong>/> -</pre> - - -<h3 id="data_object">Data Object</h3> - -<p>Let’s assume for now that you have a plain-old Java object (POJO) for User:</p> -<pre class=prettyprint> -<strong>public class </strong>User { - <strong>public final </strong>String <strong>firstName</strong>; - <strong>public final </strong>String <strong>lastName</strong>; - <strong>public </strong>User(String firstName, String lastName) { - <strong>this</strong>.<strong>firstName </strong>= firstName; - <strong>this</strong>.<strong>lastName </strong>= lastName; - } -} -</pre> - -<p>This type of object has data that never changes. It is common in applications -to have data that is read once and never changes thereafter. It is also -possible to use a JavaBeans objects:</p> -<pre class=prettyprint> -<strong>public class </strong>User { - <strong>private final </strong>String <strong>firstName</strong>; - <strong>private final </strong>String <strong>lastName</strong>; - <strong>public </strong>User(String firstName, String lastName) { - <strong>this</strong>.<strong>firstName </strong>= firstName; - <strong>this</strong>.<strong>lastName </strong>= lastName; - } - <strong>public </strong>String getFirstName() { - <strong>return this</strong>.<strong>firstName</strong>; - } - <strong>public </strong>String getLastName() { - <strong>return this</strong>.<strong>lastName</strong>; - } -} -</pre> - -<p>From the perspective of data binding, these two classes are equivalent. The -expression <strong><code>@{user.lastName}</code></strong> used for the TextView’s <strong><code>android:text</code></strong> attribute will access the <strong><code>firstName</code></strong> field in the former class and the <code>getFirstName()</code> method in the latter class. -</p><h3 id=binding_data>Binding Data</h3> - -<p>By default, a Binding class will be generated based on the name of the layout -file, converting it to Pascal case and suffixing “Binding” to it. The above -layout file was <code>activity_main.xml</code> so the generate class was <code>ActivityMainBinding</code>. This class holds all the bindings from the layout properties (e.g. the <code>user</code> variable) to the layout’s Views and knows how to assign values for the binding -expressions.The easiest means for creating the bindings is to do it while inflating: -</p> - -<pre class=prettyprint> -@Override -<strong>protected void </strong>onCreate(Bundle savedInstanceState) { - <strong>super</strong>.onCreate(savedInstanceState); - ActivityMainBinding binding = DataBindingUtil.<em>setContentView</em>(<strong>this</strong>, R.layout.<em><strong>main_activity</strong></em>); - User user = <strong>new </strong>User(<strong>"Test"</strong>, <strong>"User"</strong>); - binding.setUser(user); -} -</pre> - -<p>You’re done! Run the application and you’ll see Test User in the UI.Alternatively, you can get the view via: -</p><pre class=prettyprint> -MainActivityBinding binding = MainActivityBinding.<em>inflate</em>(getLayoutInflater()); -</pre> - -<p>If you are using data binding items inside a ListView or RecyclerView adapter, -you may prefer to use: -</p><pre class=prettyprint> -ListItemBinding binding = ListItemBinding.inflate(layoutInflater, viewGroup, -false); -//or -ListItemBinding binding = DataBindingUtil.<em>inflate</em>(layoutInflater, R.layout.<em><strong>list_item</strong></em>, viewGroup, <strong>false</strong>); -</pre> - - -<h2 id=layout_details>Layout Details</h2> - - -<h3 id=imports>Imports</h3> - -<p>Zero or more <strong><code>import</code></strong> elements may be used inside the <strong><code>data</code></strong> element. These allow easy reference to classes inside your layout file, just -like in Java. -</p><pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.view.View"</strong>/> -</<strong>data</strong>> -</pre> - -<p>Now, View may be used within your binding expression: -</p><pre class=prettyprint> -<<strong>TextView - android:text="@{user.lastName}" - android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:visibility="@{user.isAdult ? View.VISIBLE : View.GONE}"</strong>/> -</pre> - -<p>When there are class name conflicts, one of the classes may be renamed to an -“alias:”</p> -<pre class=prettyprint> -<<strong>import type="android.view.View"</strong>/> -<<strong>import type="com.example.real.estate.View" - alias="Vista"</strong>/> -</pre> - -<p>Now, <strong><code>Vista</code></strong> may be used to reference the <code>com.example.real.estate.View</code> and <strong><code>View</code></strong> may be used to reference <code>android.view.View </code>within the layout file.Imported types may be used as type references in variables and expressions:</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="com.example.User"</strong>/> - <<strong>import type="java.util.List"</strong>/> - <<strong>variable name="user" type="User"</strong>/> - <<strong>variable name="userList" type="List<User>"</strong>/> -</<strong>data</strong>> -… -<<strong>TextView - android:text="@{((User)(user.connection)).lastName}" - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - -<p>Imported types may also be used when referencing static fields and methods in -expressions:</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="com.example.MyStringUtils"</strong>/> - <<strong>variable name="user" type="com.example.User"</strong>/> -</<strong>data</strong>> -… -<<strong>TextView - android:text="@{MyStringUtils.capitalize(user.lastName)}" - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - -<p>Just as in Java, <code>java.lang.*</code> is imported automatically.</p> -<h3 id=variables>Variables</h3> - -<p>Any number of <strong><code>variable</code></strong> elements may be used inside the <strong><code>data</code></strong> element. Each <strong><code>variable</code></strong> element describes a property that may be set on the layout to be used in -binding expressions within the layout file.</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.graphics.drawable.Drawable"</strong>/> - <<strong>variable name="user" type="com.example.User"</strong>/> - <<strong>variable name="image" type="Drawable"</strong>/> - <<strong>variable name="note" type="String"</strong>/> -</<strong>data</strong>> -</pre> - -<p>The variable types are inspected at compile time, so if a variable implements <a href="#observable_objects">Observable</a>, <a href="#observable_collections">observable collection</a>, that should be reflected in the type. If the variable is a base class or - interface that does not implement the Observable* interface, the variables will <strong>not be</strong> observed!</p> - -<p>When there are different layout files for various configurations (e.g. -landscape or portrait), the variables will be combined. There must not be -conflicting variable definitions between these layout files.</p> - -<p>The generated binding class will have a setter and getter for each of the -described variables. The variables will take the default Java values until the -setter is called — <code>null</code> for reference types, <code>0</code> for <code>int</code>, <code>false</code> for <code>boolean</code>, etc.</p> - -<h3 id=custom_binding_class_names>Custom Binding Class Names</h3> - -<p>By default, a Binding class is generated based on the name of the layout file, -starting it with upper-case, removing underscores ( _ ) and capitalizing the -following letter and then suffixing “Binding”. This class will be placed in a -databinding package under the module package. For example, the layout file <code>contact_item.xml</code> will generate <code>ContactItemBinding</code>. If the module package is <code>com.example.my.app</code>, then it will be placed in <code>com.example.my.app.databinding</code>.</p> - -<p>Binding classes may be renamed or placed in different packages by adjusting the <strong><code>class</code></strong> attribute of the <strong><code>data</code></strong> element. For example:</p> -<pre class=prettyprint> -<<strong>data class="ContactItem"</strong>> - ... -</<strong>data</strong>> -</pre> - -<p>This generates the binding class as <code>ContactItem</code> in the databinding package in the module package. If the class should be -generated in a different package within the module package, it may be prefixed -with “.”:</p> -<pre class=prettyprint> -<<strong>data class=".ContactItem"</strong>> - ... -</<strong>data</strong>> -</pre> - -In this case, <code>ContactItem</code> is generated in the module package directly.Any package may be used if the full package is provided: -<pre class=prettyprint> -<<strong>data class="com.example.ContactItem"</strong>> - ... -</<strong>data</strong>> -</pre> - - -<h3 id=includes>Includes</h3> - -<p>Variables may be passed into an included layout's binding from the containing -layout by using the application namespace and the variable name in an -attribute:</p> -<pre class=prettyprint> -<em><?<strong></em>xml version="1.0" encoding="utf-8"<em></strong>?> -</em><<strong>layout xmlns:android="http://schemas.android.com/apk/res/android" -</strong> <strong> xmlns:bind="http://schemas.android.com/apk/res-auto"</strong>> - <<strong>data</strong>> - <<strong>variable name="user" type="com.example.User"</strong>/> - </<strong>data</strong>> - <<strong>LinearLayout - android:orientation="vertical" - android:layout_width="match_parent" - android:layout_height="match_parent"</strong>> - <<strong>include layout="@layout/name" - bind:user="@{user}"</strong>/> - <<strong>include layout="@layout/contact" - bind:user="@{user}"</strong>/> - </<strong>LinearLayout</strong>> -</<strong>layout</strong>> -</pre> - -<p>Here, there must be a <code>user</code> variable in both the <code>name.xml </code>and <code>contact.xml </code>layout files.</p> -<h3 id=expression_language>Expression Language</h3> - - -<h4 id=common_features>Common Features</h4> - -<p>The expression language looks a lot like a Java expression. These are the same:</p> -<ul> - <li> Mathematical <strong><code>+ - / * %</code></strong> - <li> String concatenation <strong><code>+</code></strong> - <li> <code>L</code>ogical <strong><code>&& ||</code></strong> - <li> Binary <strong><code>&</code> <code>|</code> <code>^</code></strong> - <li> Unary <strong><code>+ - ! ~</code></strong> - <li> Shift <strong><code>>> >>> <<</code></strong> - <li> Comparison <strong><code>== > < >= <=</code></strong> - <li> <strong><code>instanceof</code></strong> - <li> Grouping <strong><code>()</code></strong> - <li> Literals - character, String, numeric, <strong><code>null</code></strong> - <li> Cast - <li> Method calls - <li> Field access - <li> Array access <strong><code>[]</code></strong> - <li> Ternary operator <strong><code>?:</code></strong> -</ul> -<p>Examples:</p> -<pre class=prettyprint> -<strong>android:text="@{String.valueOf(index + 1)}" -android:visibility="@{age < 13 ? View.GONE : View.VISIBLE}" -android:transitionName='@{"image_" + id}'</strong> -</pre> - - -<h4 id=missing_operations>Missing Operations</h4> - -<p>A few operations are missing from the expression syntax that you can use in -Java.</p> -<ul> - <li> <strong><code>this</code></strong> - <li> <strong><code>super</code></strong> - <li> <strong><code>new</code></strong> - <li> Explicit generic invocation -</ul> - -<h4 id=null_coalescing_operator>Null Coalescing Operator</h4> - -<p>The null coalescing operator (<strong><code>??</code></strong>) chooses the left operand if it is not null or the right if it is null.</p> -<pre class=prettyprint> -<strong>android:text="@{user.displayName ?? user.lastName}"</strong> -</pre> - -<p>This is functionally equivalent to:</p> -<pre class=prettyprint> -<strong>android:text="@{user.displayName != null ? user.displayName : user.lastName}"</strong> -</pre> - - -<h4 id=property_reference>Property Reference</h4> - -<p>The first was already discussed in the <a href="#writing_your_first_data_binding_expressions">Writing your first data binding expressions</a> above: short form JavaBean references. When an expression references a -property on a class, it uses the same format for fields, getters, and -ObservableFields.</p> -<pre class=prettyprint> -<strong>android:text="@{user.lastName}"</strong> -</pre> - - -<h4 id=collections>Collections</h4> - -<p>Common collections: arrays, lists, sparse lists, and maps, may be accessed -using the <code>[]</code> operator for convenience.</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.util.SparseArray"</strong>/> - <<strong>import type="java.util.Map"</strong>/> - <<strong>import type="java.util.List"</strong>/> - <<strong>variable name="list" type="List<String>"</strong>/> - <<strong>variable name="sparse" type="SparseArray<String>"</strong>/> - <<strong>variable name="map" type="Map<String, String>"</strong>/> - <<strong>variable name="index" type="int"</strong>/> - <<strong>variable name="key" type="String"</strong>/> -</<strong>data</strong>> -… -<strong>android:text="@{list[index]}" -</strong>… -<strong>android:text="@{sparse[index]}" -</strong>… -<strong>android:text="@{map[key]}" -</strong> -</pre> - - -<h4 id=string_literals>String Literals</h4> - -<p>When using single quotes around the attribute value, it is easy to use double -quotes in the expression:</p> -<pre class=prettyprint> -<strong>android:text='@{map["firstName"]}'</strong> -</pre> - -<p>It is also possible to use double quotes to surround the attribute value. When -doing so, String literals should either use the " or back quote (`).</p> -<pre class=prettyprint> -<strong>android:text="@{map[`firstName`}" -android:text="@{map["firstName"]}"</strong> -</pre> - - -<h4 id=resources>Resources</h4> - -<p>It is possible to access resources as part of expressions using the normal -syntax:</p> -<pre class=prettyprint> -<strong>android:padding="@{large? @dimen/largePadding : @dimen/smallPadding}"</strong> -</pre> - -<p>Format strings and plurals may be evaluated by providing parameters:</p> -<pre class=prettyprint> -<strong>android:text="@{@string/nameFormat(firstName, lastName)}" -android:text="@{@plurals/banana(bananaCount)}"</strong> -</pre> - -<p>Some resources require explicit type evaluation.</p> - -<table> - <tr> - <th>Type</th> - <th>Normal Reference</th> - <th>Expression Reference</th> - </tr> - <tr> - <td> -<pre class=prettyprint> -String[]</td> - <td> -@array</td> - <td> -@stringArray</td> - </tr> - <tr> - <td> -int[]</td> - <td> -@array</td> - <td> -@intArray</td> - </tr> - <tr> - <td> -TypedArray</td> - <td> -@array</td> - <td> -@typedArray</td> - </tr> - <tr> - <td> -Animator</td> - <td> -@animator</td> - <td> -@animator</td> - </tr> - <tr> - <td> -StateListAnimator</td> - <td> -@animator</td> - <td> -@stateListAnimator</td> - </tr> - <tr> - <td> -</pre> - -color <code>int</code></td> - <td> -<pre class=prettyprint> -@color</td> - <td> -@color</td> - </tr> - <tr> - <td> -ColorStateList</td> - <td> -@color</td> - <td> -@colorStateList</td> - </tr> -</table> - -</pre> - - -<h2 id="data_objects">Data Objects</h2> - - -<p>Any plain old Java object (POJO) may be used for data binding, but modifying a -POJO will not cause the UI to update. The real power of data binding can be -used by giving your data objects the ability to notify when data changes. There -are three different data change notification mechanisms, <code>Observable </code>objects, <code>ObservableField</code>s, and <code>observable collections</code>.</p> - -<p>When one of these observable data object is bound to the UI and a property of -the data object changes, the UI will be updated automatically.</p> - -<h3 id=observable_objects>Observable Objects</h3> - - -<p>A class implementing <code>android.databinding.Observable</code> interface will allow the binding to attach a single listener to a bound object -to listen for changes of all properties on that object.</p> - -<p>The <code>Observable</code> interface has a mechanism to add and remove listeners, but notifying is up to -the developer. To make development easier, a base class, <code>BaseObservable,</code> was created to implement the listener registration mechanism. The data class -implementer is still responsible for notifying when the properties change. This -is done by assigning an <code>Bindable </code>annotation to the getter and notifying in the setter.</p> - -<pre class=prettyprint> -<strong>private static class </strong>User <strong>extends </strong>BaseObservable { - <strong>private </strong>String <strong>firstName</strong>; - <strong>private </strong>String <strong>lastName</strong>; - @Bindable - <strong>public </strong>String getFirstName() { - <strong>return this</strong>.<strong>firstName</strong>; - } - @Bindable - <strong>public </strong>String getFirstName() { - <strong>return this</strong>.<strong>lastName</strong>; - } - <strong>public void </strong>setFirstName(String firstName) { - <strong>this</strong>.<strong>firstName </strong>= firstName; - notifyPropertyChanged(BR.firstName); - } - <strong>public void </strong>setLastName(String lastName) { - <strong>this</strong>.<strong>lastName </strong>= lastName; - notifyPropertyChanged(BR.lastName); - } -} -</pre> - -<p>The <code>Bindable </code>annotation generates an entry in the BR class file during compilation. The BR -class file will be generated in the module package.If the base class for data classes cannot be changed, the <code>Observable</code> interface may be implemented using the convenient <code>PropertyChangeRegistry</code> to store and notify listeners efficiently.</p> - -<h3 id=observablefields>ObservableFields</h3> - -<p>A little work is involved in creating Observable classes, so developers who -want to save time or have few properties may use ObservableFields. -ObservableFields are self-contained observable objects that have a single -field. There are versions for all primitive types and one for reference types. -To use, create a public final field in the data class:</p> -<pre class=prettyprint> -<strong>private static class </strong>User <strong>extends </strong>BaseObservable { - <strong>public final </strong>ObservableField<String> <strong>firstName </strong>= - <strong>new </strong>ObservableField<>(); - <strong>public final </strong>ObservableField<String> <strong>lastName </strong>= - <strong>new </strong>ObservableField<>(); - <strong>public final </strong>ObservableInt <strong>age </strong>= <strong>new </strong>ObservableInt(); -} -</pre> - -<p>That's it! To access the value, use the set and get accessor methods:</p> -<pre class=prettyprint> -user.<strong>firstName</strong>.set(<strong>"Google"</strong>); -<strong>int </strong>age = user.<strong>age</strong>.get(); -</pre> - - -<h3 id=observable_collections>Observable Collections</h3> - -<p>Some applications use more dynamic structures to hold data. Observable - collections allow keyed access to these data objects.ObservableArrayMap is useful when the key is a reference type, such as String.</p> - -<pre class=prettyprint> -ObservableArrayMap<String, Object> user = <strong>new </strong>ObservableArrayMap<>(); -user.put(<strong>"firstName"</strong>, <strong>"Google"</strong>); -user.put(<strong>"lastName"</strong>, <strong>"Inc."</strong>); -user.put(<strong>"age"</strong>, 17); -</pre> - -In the layout, the map may be accessed through the String keys: -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.databinding.ObservableMap"</strong>/> - <<strong>variable name="user" type="ObservableMap<String, Object>"</strong>/> -</<strong>data</strong>> -… -<<strong>TextView - android:text='@{user["lastName"]}' - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -<<strong>TextView - android:text='@{String.valueOf(1 + (Integer)user["age"])}' - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - -<p>ObservableArrayList is useful when the key is an integer:</p> -<pre class=prettyprint> -ObservableArrayList<Object> user = <strong>new </strong>ObservableArrayList<>(); -user.add(<strong>"Google"</strong>); -user.add(<strong>"Inc."</strong>); -user.add(17); -</pre> - -<p>In the layout, the list may be accessed through the indices:</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.databinding.ObservableList"</strong>/> - <<strong>import type="com.example.my.app.Fields"</strong>/> - <<strong>variable name="user" type="ObservableList<Object>"</strong>/> -</<strong>data</strong>> -… -<<strong>TextView - android:text='@{user[Fields.LAST_NAME]}' - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -<<strong>TextView - android:text='@{String.valueOf(1 + (Integer)user[Fields.AGE])}' - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - - -<h2 id=generated_binding>Generated Binding</h2> - -<p>The generated binding class links the layout variables with the Views within -the layout. As discussed earlier, the name and package of the Binding may be <a href="#custom_binding_class_names">customized</a>. The Generated binding classes all extend <code>android.databinding.ViewDataBinding</code>.</p> -<h3 id=creating>Creating</h3> - -<p>The binding should be created soon after inflation to ensure that the View -hierarchy is not disturbed prior to binding to the Views with expressions -within the layout. There are a few ways to bind to a layout. The most common is -to use the static methods on the Binding class.The inflate method inflates the View hierarchy and binds to it all it one step. -There are versions that attach the View to its parent and that inflate without -attaching.</p> -<pre class=prettyprint> -MyLayoutBinding binding = MyLayoutBinding.<em>inflate</em>(<strong>this</strong>); -MyLayoutBinding binding = MyLayoutBinding.<em>inflate</em>(viewGroup); -</pre> - -<p>If the layout was inflated using a different mechanism, it may be bound -separately:</p> -<pre class=prettyprint> -MyLayoutBinding binding = MyLayoutBinding.<em>bind</em>(viewRoot); -</pre> - -<p>Sometimes the binding cannot be known in advance. In such cases, the binding -can be created using the DataBindingUtil class:</p> -<pre class=prettyprint> -ViewDataBinding binding = DataBindingUtil.<em>inflate</em>(context, layoutId, - parent, attachToParent); -ViewDataBinding binding = DataBindingUtil.<em>bindTo</em>(viewRoot, layoutId); -</pre> - - -<h3 id=views_with_ids>Views With IDs</h3> - -<p>A public final field will be generated for each View with an ID in the layout. -The binding does a single pass on the View hierarchy, extracting the Views with -IDs. This mechanism can be faster than calling findViewById for several Views. For example:</p> -<pre class=prettyprint> -<<strong>layout xmlns:android="http://schemas.android.com/apk/res/android"</strong>> - <<strong>data</strong>> - <<strong>variable name="user" type="com.example.User"</strong>/> - </<strong>data</strong>> - <<strong>LinearLayout - android:orientation="vertical" - android:layout_width="match_parent" - android:layout_height="match_parent"</strong>> - <<strong>TextView android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@{user.firstName}" -</strong> <strong>android:id="@+id/firstName"</strong>/> - <<strong>TextView android:layout_width="wrap_content" - android:layout_height="wrap_content" - android:text="@{user.lastName}"</strong> <strong>android:id="@+id/lastName"</strong>/> - </<strong>LinearLayout</strong>> -</<strong>layout</strong>> -</pre> - -Will generate a binding class with: -<pre class=prettyprint> -<strong>public final </strong>TextView <strong>firstName</strong>; -<strong>public final </strong>TextView <strong>lastName</strong>; -</pre> - -<p>IDs are not nearly as necessary as without data binding, but there are still -some instances where access to Views are still necessary from code.</p> -<h3 id=variables>Variables</h3> - -<p>Each variable will be given a accessor methods.</p> -<pre class=prettyprint> -<<strong>data</strong>> - <<strong>import type="android.graphics.drawable.Drawable"</strong>/> - <<strong>variable name="user" type="com.example.User"</strong>/> - <<strong>variable name="image" type="Drawable"</strong>/> - <<strong>variable name="note" type="String"</strong>/> -</<strong>data</strong>> -</pre> - -<p>will generate setters and getters in the binding:</p> -<pre class=prettyprint> -<strong>public abstract </strong>com.example.User getUser(); -<strong>public abstract void </strong>setUser(com.example.User user); -<strong>public abstract </strong>Drawable getImage(); -<strong>public abstract void </strong>setImage(Drawable image); -<strong>public abstract </strong>String getNote(); -<strong>public abstract void </strong>setNote(String note); -</pre> - - -<h3 id=viewstubs>ViewStubs</h3> - -<p>ViewStubs are a little different from normal Views. They start off invisible -and when they either are made visible or are explicitly told to inflate, they -replace themselves in the layout by inflating another layout.</p> - -<p>Because the ViewStub essentially disappears from the View hierarchy, the View -in the binding object must also disappear to allow collection. Because the -Views are final, a ViewStubProxy object takes the place of the ViewStub, giving -the developer access to the ViewStub when it exists and also access to the -inflated View hierarchy when the ViewStub has been inflated.</p> - -<p>When inflating another layout, a binding must be established for the new -layout. Therefore, the ViewStubProxy must listen to the ViewStub's -OnInflateListener and establish the binding at that time. Since only one can -exist, the ViewStubProxy allows the developer to set an OnInflateListener on it -that it will call after establishing the binding.</p> - -<h3 id=advanced_binding>Advanced Binding</h3> - - -<h4 id=dynamic_variables>Dynamic Variables</h4> - -<p>At times, the specific binding class won't be known. For example, a -RecyclerView Adapter operating against arbitrary layouts won't know the -specific binding class. It still must assign the binding value during the -onBindViewHolder.</p> - -<p>In this example, all layouts that the RecyclerView binds to have an "item" -variable. The BindingHolder has a getBinding method returning the <code>ViewDataBinding</code> base.</p> -<pre class=prettyprint> -<strong>public void </strong>onBindViewHolder(BindingHolder holder, <strong>int </strong>position) { - <strong>final </strong>T item = <strong>mItems</strong>.get(position); - holder.getBinding().setVariable(BR.item, item); - holder.getBinding().executePendingBindings(); -} -</pre> - - -<h4 id=immediate_binding>Immediate Binding</h4> - -<p>When a variable or observable changes, the binding will be scheduled to change -before the next frame. There are times, however, when binding must be executed -immediately. To force execution, use the executePendingBindings() method.</p> -<h2 id=attribute_setters>Attribute Setters</h2> - -<p>Whenever a bound value changes, the generated binding class must call a setter -method on the View with the binding expression. The data binding framework has -ways to customize which method to call to set the value.</p> -<h3 id=automatic_setters>Automatic Setters</h3> - -For an attribute, data binding tries to find the method setAttribute. The -namespace for the attribute does not matter, only the attribute name itself. - -<p>For example, an expression associated with TextView's attribute <strong><code>android:text</code></strong> will look for a setText(String). If the expression returns an int, data -binding will search for a setText(int) method. Be careful to have the -expression return the correct type, casting if necessary.Note that data binding will work even if no attribute exists with the given -name. You can then easily "create" attributes for any setter by using data -binding. For example, support DrawerLayout doesn't have any attributes, but -plenty of setters. You can use the automatic setters to use one of these.</p> -<pre class=prettyprint> -<android.support.v4.widget.<strong>DrawerLayout - android:layout_width="wrap_content" - android:layout_height="wrap_content" - app:scrimColor="@{@color/scrim}" - app:drawerListener="@{fragment.drawerListener}"/></strong> -</pre> - - -<h3 id=renamed_setters>Renamed Setters</h3> - -<p>Some attributes have setters that don't match by name. For these methods, an -attribute may be associated with the setter through BindingMethods annotation. -This must be associated with a class and contains BindingMethod annotations, -one for each renamed method. For example, the <strong><code>android:tint</code></strong> attribute is really associated with setImageTintList, not setTint.</p> -<pre class=prettyprint> -@BindingMethods({ - @BindingMethod(type = <strong>"android.widget.ImageView"</strong>, - attribute = <strong>"android:tint"</strong>, - method = <strong>"setImageTintList"</strong>), -}) -</pre> - -<p>It is unlikely that developers will need to rename setters; the android -framework attributes have already been implemented.</p> -<h3 id=custom_setters>Custom Setters</h3> - -<p>Some attributes need custom binding logic. For example, there is no associated -setter for the <strong><code>android:paddingLeft</code></strong> attribute. Instead, setPadding(left, top, right, bottom) exists. A static -binding adapter method with the BindingAdapter annotation allows the developer -to customize how a setter for an attribute is called.</p> - -<p>The android attributes have already had BindingAdapters created. For example, -here is the one for paddingLeft:</p> -<pre class=prettyprint></p> -@BindingAdapter(<strong>"android:paddingLeft"</strong>) -<strong>public static void </strong>setPaddingLeft(View view, <strong>int </strong>padding) { - view.setPadding(padding, - view.getPaddingTop(), - view.getPaddingRight(), - view.getPaddingBottom()); -} -</pre> - -<p>Binding adapters are useful for other types of customization. For example, a - custom loader can be called off-thread to load an image.</p> - -<p>Developer-created binding adapters will override the data binding default -adapters when there is a conflict.</p> - -<p>You can also have adapters that receive multiple parameters. </p> -<pre class=prettyprint> -@BindingAdapter(attributes = {<strong>"bind:imageUrl"</strong>, <strong>"bind:error"</strong>}) -<strong>public static void </strong>loadImage(ImageView view, String url, Drawable error) { - Picasso.<em>with</em>(view.getContext()).load(url).error(error).into(view); -} -</pre> - -<p>This adapter will be called if both <strong>imageUrl </strong>and <strong>error </strong>are used for an ImageView and <em>imageUrl </em>is a string and <em>error</em> is a drawable.</p> -<ul> - <li> Custom namespaces are ignore during matching. - <li> You can also write adapters for android namespace. -</ul> - -<pre class=prettyprint> -<ImageView app:imageUrl=“@{venue.imageUrl}” -app:error=“@{@drawable/venueError}”/> -</pre> - - -<h2 id=converters>Converters</h2> - - -<h3 id=object_conversions>Object Conversions</h3> - -<p>When an Object is returned from a binding expression, a setter will be chosen -from the automatic, renamed, and custom setters. The Object will be cast to a -parameter type of the chosen setter.</p><p>This is a convenience for those using ObservableMaps to hold data. for example:</p> -<pre class=prettyprint> -<<strong>TextView - android:text='@{userMap["lastName"]}' - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - -<p>The userMap returns an Object and that Object will be automatically cast to -parameter type found in the setter <code>setText(CharSequence)</code>. When there may be confusion about the parameter type, the developer will need -to cast in the expression.</p> -<h3 id=custom_conversions>Custom Conversions</h3> - -<p>Sometimes conversions should be automatic between specific types. For example, -when setting the background:</p> -<pre class=prettyprint> -<<strong>View - android:background="@{isError ? @color/red : @color/white}" - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - -<p>Here, the background takes a <code>Drawable</code>, but the color is an integer. Whenever a <code>Drawable</code> is expected and an integer is returned, the <code>int</code> should be converted to a <code>ColorDrawable</code>. This conversion is done using a static method with a BindingConversion -annotation:</p> -<pre class=prettyprint> -@BindingConversion -<strong>public static </strong>ColorDrawable convertColorToDrawable(<strong>int </strong>color) { - <strong>return new </strong>ColorDrawable(color); -} -</pre> - -<p>Note that conversions only happen at the setter level, so it is <strong>not allowed </strong>to mix types like this:</p> -<pre class=prettyprint> -<<strong>View - android:background="@{isError ? @drawable/error : @color/white}" - android:layout_width="wrap_content" - android:layout_height="wrap_content"</strong>/> -</pre> - |