diff options
Diffstat (limited to 'docs/html/guide/tutorials/notepad/notepad-ex1.jd')
| -rw-r--r-- | docs/html/guide/tutorials/notepad/notepad-ex1.jd | 589 |
1 files changed, 589 insertions, 0 deletions
diff --git a/docs/html/guide/tutorials/notepad/notepad-ex1.jd b/docs/html/guide/tutorials/notepad/notepad-ex1.jd new file mode 100644 index 0000000..b7f42bf --- /dev/null +++ b/docs/html/guide/tutorials/notepad/notepad-ex1.jd @@ -0,0 +1,589 @@ +page.title=Notepad Exercise 1 +parent.title=Notepad Tutorial +parent.link=index.html +@jd:body + + +<p><em>In this exercise, you will construct a simple notes list that lets the +user add new notes but not edit them. The exercise demonstrates:</em></p> +<ul> +<li><em>The basics of <code>ListActivities</code> and creating and handling menu +options. </em></li> +<li><em>How to use a SQLite database to store the notes.</em></li> +<li><em>How to bind data from a database cursor into a ListView using a +SimpleCursorAdapter.</em></li> +<li><em>The basics of screen layouts, including how to lay out a list view, how +you can add items to the activity menu, and how the activity handles those menu +selections. </em></li> +</ul> + +<div style="float:right;white-space:nowrap"> +<span style="color:#BBB;"> + [<a href="notepad-ex1.html" style="color:#BBB;">Exercise 1</a>]</span> + [<a href="notepad-ex2.html">Exercise 2</a>] + [<a href="notepad-ex3.html">Exercise 3</a>] + [<a href="notepad-extra-credit.html">Extra Credit</a>] +</div> + + + +<h2>Step 1</h2> + + <p>Open up the <code>Notepadv1</code> project in Eclipse.</p> + + <p><code>Notepadv1</code> is a project that is provided as a starting point. It + takes care of some of the boilerplate work that you have already seen if you + followed the <a href="{@docRoot}guide/tutorials/hello-world.html">Hello, + World</a> tutorial.</p> + + <ol> + <li> + Start a new Android Project by clicking <strong>File</strong> > + <strong>New</strong> > <strong>Android Project</strong>.</li> + <li> + In the New Android Project dialog, select <strong>Create project from existing source</strong>.</li> + <li> + Click <strong>Browse</strong> and navigate to where you copied the <code>NotepadCodeLab</code> + (downloaded during <a href="{@docRoot}guide/tutorials/notepad/index.html#preparing">setup</a>). Select + <code>Notepadv1</code> and click <strong>Choose</strong>.</li> + <li> + You should see <code>Notepadv1</code> in the <em>Project name</em> and also see the <em>Location</em> + filled in with the path you selected.</li> + <li> + Click <strong>Finish</strong>. The <code>Notepadv1</code> project should open and be + visible in your Eclipse package explorer.</li> + </ol> + + <p>If you see an error about <code>AndroidManifest.xml</code>, or some + problems related to an Android zip file, right click on the project and + select <strong>Android Tools</strong> > <strong>Fix Project Properties</strong>. + (The project is looking in the wrong location for the library file, + this will fix it for you.)</p> + + <h2>Step 2</h2> + + <div class="sidebox" style="border:2px solid #FFFFDD;float:right; + background-color:#FFFFEE;margin-right:0px; + margin-bottom:.5em;margin-top:1em;padding:0em;width:240px;"> + <h2 style="border:0;font-size:12px;padding:.5em .5em .5em 1em;margin:0; + background-color:#FFFFDD;">Accessing and modifying data</h2> + <p style="padding-left:.5em;font-size:12px;margin:0; padding:.0em .5em .5em 1em;">For this + exercise, we are using a SQLite database to store our data. This is useful + if only <em>your</em> application will need to access or modify the data. If you wish for + other activities to access or modify the data, you have to expose the data using a + {@link android.content.ContentProvider ContentProvider}.</p> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">If you are interested, you can find out more about + <a href="{@docRoot}guide/topics/providers/content-providers.html">content providers</a> or the whole + subject of <a href="{@docRoot}guide/topics/data/data-storage.html">Data Storage</a>. + The NotePad sample in the <code>samples/</code> folder of the SDK also has an example of how + to create a ContentProvider.</p> + </div> + + <p>Take a look at the <code>NotesDbAdapter</code> class — this class is provided to + encapsulate data access to a SQLite database that will hold our notes data + and allow us to update it.</p> + <p>At the top of the class are some constant definitions that will be used in the application + to look up data from the proper field names in the database. There is also a database creation + string defined, which is used to create a new database schema if one doesn't exist already.</p> + <p>Our database will have the name <code>data</code>, and have a single table called + <code>notes</code>, which in turn has three fields: <code>_id</code>, <code>title</code> and + <code>body</code>. The <code>_id</code> is named with an underscore convention used in a number of + places inside the Android SDK and helps keep a track of state. The <code>_id</code> + usually has to be specified when querying or updating the database (in the column projections + and so on). The other two fields are simple text fields that will store data. + </p> + <p>The constructor for <code>NotesDbAdapter</code> takes a Context, which allows it to communicate with aspects + of the Android operating system. This is quite common for classes that need to touch the + Android system in some way. The Activity class implements the Context class, so usually you will just pass + <code>this</code> from your Activity, when needing a Context.</p> + <p>The <code>open()</code> method calls up an instance of DatabaseHelper, which is our local + implementation of the SQLiteOpenHelper class. It calls <code>getWritableDatabase()</code>, + which handles creating/opening a database for us.</p> + <p><code>close()</code> just closes the database, releasing resources related to the + connection.</p> + <p><code>createNote()</code> takes strings for the title and body of a new note, + then creates that note in the database. Assuming the new note is created successfully, the + method also returns the row <code>_id</code> value for the newly created note.</p> + <p><code>deleteNote()</code> takes a <var>rowId</var> for a particular note, and deletes that note from + the database.</p> + + <p><code>fetchAllNotes()</code> issues a query to return a {@link android.database.Cursor} over all notes in the + database. The <code>query()</code> call is worth examination and understanding. The first field is the + name of the database table to query (in this case <code>DATABASE_TABLE</code> is "notes"). + The next is the list of columns we want returned, in this case we want the <code>_id</code>, + <code>title</code> and <code>body</code> columns so these are specified in the String array. + The remaining fields are, in order: <code>selection</code>, + <code>selectionArgs</code>, <code>groupBy</code>, <code>having</code> and <code>orderBy</code>. + Having these all <code>null</code> means we want all data, need no grouping, and will take the default + order. See {@link android.database.sqlite.SQLiteDatabase SQLiteDatabase} for more details.</p> + <p class="note"><b>Note:</b> A Cursor is returned rather than a collection of rows. This allows + Android to use resources efficiently -- instead of putting lots of data straight into memory + the cursor will retrieve and release data as it is needed, which is much more efficient for + tables with lots of rows.</p> + + <p><code>fetchNote()</code> is similar to <code>fetchAllNotes()</code> but just gets one note + with the <var>rowId</var> we specify. It uses a slightly different version of the + {@link android.database.sqlite.SQLiteDatabase} <code>query()</code> method. + The first parameter (set <em>true</em>) indicates that we are interested + in one distinct result. The <var>selection</var> parameter (the fourth parameter) has been specified to search + only for the row "where _id =" the <var>rowId</var> we passed in. So we are returned a Cursor on + the one row.</p> + <p>And finally, <code>updateNote()</code> takes a <var>rowId</var>, <var>title</var> and <var>body</var>, and uses a + {@link android.content.ContentValues ContentValues} instance to update the note of the given + <var>rowId</var>.</p> + +<h2 style="clear:right;">Step 3</h2> + + <div class="sidebox" style="border:2px solid #FFFFDD;float:right; + background-color:#FFFFEE;margin-right:0px; + margin-bottom:.5em;margin-top:1em;padding:0em;width:240px;"> + <h2 style="border:0;font-size:12px;padding:.5em .5em .5em 1em;margin:0; + background-color:#FFFFDD;">Layouts and activities</h2> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">Most Activity classes will have a layout associated with them. The layout + will be the "face" of the Activity to the user. In this case our layout will + take over the whole screen and provide a list of notes.</p> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">Full screen layouts are not the only option for an Activity however. You + might also want to use a <a +href="{@docRoot}guide/appendix/faq/commontasks.html#floatingorfull">floating + layout</a> (for example, a <a +href="{@docRoot}guide/appendix/faq/commontasks.html#dialogsandalerts">dialog + or alert</a>), + or perhaps you don't need a layout at all (the Activity will be invisible + to the user unless you specify some kind of layout for it to use).</p> + </div> + + <p>Open the <code>notepad_list.xml</code> file in <code>res/layout</code> +and + take a look at it. (You may have to + hit the <em>xml</em> tab, at the bottom, in order to view the XML markup.)</p> + + <p>This is a mostly-empty layout definition file. Here are some + things you should know about a layout file:</p> + + + <ul> + <li> + All Android layout files must start with the XML header line: + <code><?xml version="1.0" encoding="utf-8"?></code>. </li> + <li> + The next definition will often (but not always) be a layout + definition of some kind, in this case a <code>LinearLayout</code>. </li> + <li> + The XML namespace of Android should always be defined in + the top level component or layout in the XML so that <code>android:</code> tags can + be used through the rest of the file: + <p><code>xmlns:android="http://schemas.android.com/apk/res/android"</code></p> + </li> + </ul> + + <h2 style="clear:right;">Step 4</h2> + <p>We need to create the layout to hold our list. Add code inside + of the <code>LinearLayout</code> element so the whole file 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="wrap_content" + android:layout_height="wrap_content"> + + <ListView android:id="@android:id/list" + android:layout_width="wrap_content" + android:layout_height="wrap_content"/> + <TextView android:id="@android:id/empty" + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:text="@string/no_notes"/> + +</LinearLayout> +</pre> + <ul> + <li> + The <strong>@</strong> symbol in the id strings of the <code>ListView</code> and + <code>TextView</code> tags means + that the XML parser should parse and expand the rest of + the id string and use an ID resource.</li> + <li> + The <code>ListView</code> and <code>TextView</code> can be + thought as two alternative views, only one of which will be displayed at once. + ListView will be used when there are notes to be shown, while the TextView + (which has a default value of "No Notes Yet!" defined as a string + resource in <code>res/values/strings.xml</code>) will be displayed if there + aren't any notes to display.</li> + <li>The <code>list</code> and <code>empty</code> IDs are + provided for us by the Android platform, so, we must + prefix the <code>id</code> with <code>android:</code> (e.g., <code>@android:id/list</code>).</li> + <li>The View with the <code>empty</code> id is used + automatically when the {@link android.widget.ListAdapter} has no data for the ListView. The + ListAdapter knows to look for this name by default. Alternatively, you could change the + default empty view by using {@link android.widget.AdapterView#setEmptyView(View)} + on the ListView. + <p> + More broadly, the <code>android.R</code> class is a set of predefined + resources provided for you by the platform, while your project's + <code>R</code> class is the set of resources your project has defined. + Resources found in the <code>android.R</code> resource class can be + used in the XML files by using the <code>android:</code> name space prefix + (as we see here).</p> + </li> + </ul> + + <h2 style="clear:right;">Step 5</h2> + + <div class="sidebox" style="border:2px solid #FFFFDD;float:right; + background-color:#FFFFEE;margin-right:0px; + margin-bottom:.5em;margin-top:1em;padding:0em;width:240px;"> + <h2 style="border:0;font-size:12px;padding:.5em .5em .5em 1em;margin:0; + background-color:#FFFFDD;">Resources and the R class</h2> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">The folders under res/ in the Eclipse project are for resources. + There is a <a href="{@docRoot}guide/appendix/faq/commontasks.html#filelist">specific structure</a> to the + folders and files under res/.</p> + <p style="padding-left:.5em;font-size:12px; +margin:0; padding:.0em .5em .5em 1em;">Resources defined in these folders and files will have + corresponding entries in the R class allowing them to be easily accessed + and used from your application. The R class is automatically generated using the contents + of the res/ folder by the eclipse plugin (or by aapt if you use the command line tools). + Furthermore, they will be bundled and deployed for you as part of the application.</p> + </p> + </div> + <p>To make the list of notes in the ListView, we also need to define a View for each row:</p> + <ol> + <li> + Create a new file under <code>res/layout</code> called + <code>notes_row.xml</code>. </li> + <li> + Add the following contents (note: again the XML header is used, and the + first node defines the Android XML namespace)<br> + <pre style="overflow:auto"> +<?xml version="1.0" encoding="utf-8"?> +<TextView android:id="@+id/text1" + xmlns:android="http://schemas.android.com/apk/res/android" + android:layout_width="wrap_content" + android:layout_height="wrap_content"/></pre> + <p> + This is the View that will be used for each notes title row — it has only + one text field in it. </p> + <p>In this case we create a new id called <code>text1</code>. The + <strong>+</strong> after the <strong>@</strong> in the id string indicates that the id should + be automatically created as a resource if it does not already exist, so we are defining + <code>text1</code> on the fly and then using it.</p> + </li> + <li>Save the file.</li> + </ol> + <p>Open the <code>R.java</code> class in the + project and look at it, you should see new definitions for + <code>notes_row</code> and <code>text1</code> (our new definitions) + meaning we can now gain access to these from the our code. </p> + + <h2 style="clear:right;">Step 6</h2> +<p>Next, open the <code>Notepadv1</code> class in the source. In the following steps, we are going to + alter this class to become a list adapter and display our notes, and also + allow us to add new notes.</p> + +<p><code>Notepadv1</code> will inherit from a subclass + of <code>Activity</code> called a <code>ListActivity</code>, + which has extra functionality to accommodate the kinds of + things you might want to do with a list, for + example: displaying an arbitrary number of list items in rows on the screen, + moving through the list items, and allowing them to be selected.</p> + +<p>Take a look through the existing code in <code>Notepadv1</code> class. + There is a currently an unused private field called <code>mNoteNumber</code> that + we will use to create numbered note titles.</p> + <p>There are also three override methods defined: + <code>onCreate</code>, <code>onCreateOptionsMenu</code> and + <code>onOptionsItemSelected</code>; we need to fill these + out:</p> + <ul> + <li><code>onCreate()</code> is called when the activity is + started — it is a little like the "main" method for an Activity. We use + this to set up resources and state for the activity when it is + running.</li> + <li><code>onCreateOptionsMenu()</code> is used to populate the + menu for the Activity. This is shown when the user hits the menu button, +and + has a list of options they can select (like "Create + Note"). </li> + <li><code>onOptionsItemSelected()</code> is the other half of the + menu equation, it is used to handle events generated from the menu (e.g., + when the user selects the "Create Note" item). + </li> + </ul> + + <h2>Step 7</h2> + <p>Change the inheritance of <code>Notepadv1</code> from +<code>Activity</code> + to <code>ListActivity</code>:</p> + <pre>public class Notepadv1 extends ListActivity</pre> + <p>Note: you will have to import <code>ListActivity</code> into the +Notepadv1 + class using Eclipse, <strong>ctrl-shift-O</strong> on Windows or Linux, or + <strong>cmd-shift-O</strong> on the Mac (organize imports) will do this for you + after you've written the above change.</p> + + <h2>Step 8</h2> + <p>Fill out the body of the <code>onCreate()</code> method.</p> + <p>Here we will set the title for the Activity (shown at the top of the + screen), use the <code>notepad_list</code> layout we created in XML, + set up the <code>NotesDbAdapter</code> instance that will + access notes data, and populate the list with the available note + titles:</p> + <ol> + <li> + In the <code>onCreate</code> method, call <code>super.onCreate()</code> with the + <code>savedInstanceState</code> parameter that's passed in.</li> + <li> + Call <code>setContentView()</code> and pass <code>R.layout.notepad_list</code>.</li> + <li> + At the top of the class, create a new private class field called <code>mDbHelper</code> of class + <code>NotesDbAdapter</code>. + </li> + <li> + Back in the <code>onCreate</code> method, construct a new +<code>NotesDbAdapter</code> + instance and assign it to the <code>mDbHelper</code> field (pass + <code>this</code> into the constructor for <code>DBHelper</code>) + </li> + <li> + Call the <code>open()</code> method on <code>mDbHelper</code> to open (or create) the + database. + </li> + <li> + Finally, call a new method <code>fillData()</code>, which will get the data and + populate the ListView using the helper — we haven't defined this method yet. </li> + </ol> + <p> + <code>onCreate()</code> should now look like this:</p> + <pre> + @Override + public void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + setContentView(R.layout.notepad_list); + mDbHelper = new NotesDbAdapter(this); + mDbHelper.open(); + fillData(); + }</pre> + <p>And be sure you have the <code>mDbHelper</code> field definition (right + under the mNoteNumber definition): </p> + <pre> private NotesDbAdapter mDbHelper;</pre> + + <h2>Step 9</h2> + + <div class="sidebox" style="border:2px solid #FFFFDD;float:right; + background-color:#FFFFEE;margin-right:0px; + margin-bottom:.5em;margin-top:1em;padding:0em;width:240px;"> + <h2 style="border:0;font-size:12px;padding:.5em .5em .5em 1em;margin:0; + background-color:#FFFFDD;">More on menus</h2> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">The notepad application we are constructing only scratches the + surface with <a href="{@docRoot}guide/appendix/faq/commontasks.html#addmenuitems">menus</a>. </p> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">You can also <a href="{@docRoot}guide/appendix/faq/commontasks.html#menukeyshortcuts">add +shortcut keys for menu items</a>, <a href="{@docRoot}guide/appendix/faq/commontasks.html#menukeyshortcuts">create +submenus</a> and even <a href="{@docRoot}guide/appendix/faq/commontasks.html#addingtoothermenus">add +menu items to other applications!</a>. </p> + </div> + +<p>Fill out the body of the <code>onCreateOptionsMenu()</code> method.</p> + +<p>We will now create the "Add Item" button that can be accessed by pressing the menu +button on the device. We'll specify that it occupy the first position in the menu.</p> + + <ol> + <li> + In <code>strings.xml</code> resource (under <code>res/values</code>), add + a new string named "menu_insert" with its value set to <code>Add Item</code>: + <pre><string name="menu_insert">Add Item</string></pre> + <p>Then save the file and return to <code>Notepadv1</code>.</p> + </li> + <li>Create a menu position constant at the top of the class: + <pre>public static final int INSERT_ID = Menu.FIRST;</pre> + </li> + <li>In the <code>onCreateOptionsMenu()</code> method, change the + <code>super</code> call so we capture the boolean return as <code>result</code>. We'll return this value at the end.</li> + <li>Then add the menu item with <code>menu.add()</code>.</li> + </ol> + <p>The whole method should now look like this: + <pre> + @Override + public boolean onCreateOptionsMenu(Menu menu) { + boolean result = super.onCreateOptionsMenu(menu); + menu.add(0, INSERT_ID, 0, R.string.menu_insert); + return result; + }</pre> + <p>The arguments passed to <code>add()</code> indicate: a group identifier for this menu (none, + in this case), a unique ID (defined above), the order of the item (zero indicates no preference), + and the resource of the string to use for the item.</p> + +<h2 style="clear:right;">Step 10</h2> + <p>Fill out the body of the <code>onOptionsItemSelected()</code> method:</p> + <p>This is going + to handle our new "Add Note" menu item. When this is selected, the + <code>onOptionsItemSelected()</code> method will be called with the + <code>item.getId()</code> set to <code>INSERT_ID</code> (the constant we + used to identify the menu item). We can detect this, and take the + appropriate actions:</p> + <ol> + <li> + The <code>super.onOptionsItemSelected(item)</code> method call goes at the + end of this method — we want to catch our events first! </li> + <li> + Write a switch statement on <code>item.getItemId()</code>. + <p>In the case of <var>INSERT_ID</var>, call a new method, <code>createNote()</code>, + and return true, because we have handled this event and do not want to + propagate it through the system.</p> + </li> + <li>Return the result of the superclass' <code>onOptionsItemSelected()</code> + method at the end.</li> + </ol> + <p> + The whole <code>onOptionsItemSelect()</code> method should now look like + this:</p> + <pre> + @Override + public boolean onOptionsItemSelected(MenuItem item) { + switch (item.getItemId()) { + case INSERT_ID: + createNote(); + return true; + } + + return super.onOptionsItemSelected(item); + }</pre> + +<h2>Step 11</h2> + <p>Add a new <code>createNote()</code> method:</p> + <p>In this first version of + our application, <code>createNote()</code> is not going to be very useful. +We will simply + create a new note with a title assigned to it based on a counter ("Note 1", + "Note 2"...) and with an empty body. At present we have no way of editing + the contents of a note, so for now we will have to be content making one + with some default values:</p> + <ol> + <li>Construct the name using "Note" and the counter we defined in the class: <code> + String noteName = "Note " + mNoteNumber++</code></li> + <li> + Call <code>mDbHelper.createNote()</code> using <code>noteName</code> as the + title and <code>""</code> for the body + </li> + <li> + Call <code>fillData()</code> to populate the list of notes (inefficient but + simple) — we'll create this method next.</li> + </ol> + <p> + The whole <code>createNote()</code> method should look like this: </p> + <pre> + private void createNote() { + String noteName = "Note " + mNoteNumber++; + mDbHelper.createNote(noteName, ""); + fillData(); + }</pre> + + +<h2>Step 12</h2> + <div class="sidebox" style="border:2px solid #FFFFDD;float:right; + background-color:#FFFFEE;margin-right:0px; + margin-bottom:.5em;margin-top:1em;padding:0em;width:240px;"> + <h2 style="border:0;font-size:12px;padding:.5em .5em .5em 1em;margin:0; + background-color:#FFFFDD;">List adapters</h2> + <p style="padding-left:.5em;font-size:12px;margin:0; + padding:.0em .5em .5em 1em;">Our example uses a {@link android.widget.SimpleCursorAdapter + SimpleCursorAdapter} to bind a database {@link android.database.Cursor Cursor} + into a ListView, and this is a common way to use a {@link android.widget.ListAdapter + ListAdapter}. Other options exist like {@link android.widget.ArrayAdapter ArrayAdapter} which + can be used to take a List or Array of in-memory data and bind it in to + a list as well.</p> + </div> + + <p>Define the <code>fillData()</code> method:</p> + <p>This + method uses <code>SimpleCursorAdapter,</code> which takes a database <code>Cursor</code> + and binds it to fields provided in the layout. These fields define the row elements of our list + (in this case we use the <code>text1</code> field in our + <code>notes_row.xml</code> layout), so this allows us to easily populate the list with + entries from our database.</p> + <p>To do this we have to provide a mapping from the <code>title</code> field in the returned Cursor, to + our <code>text1</code> TextView, which is done by defining two arrays: the first a string array + with the list of columns to map <em>from</em> (just "title" in this case, from the constant + <code>NotesDbAdapter.KEY_TITLE</code>) and, the second, an int array + containing references to the views that we'll bind the data <em>into</em> + (the <code>R.id.text1</code> TextView).</p> + <p>This is a bigger chunk of code, so let's first take a look at it:</p> + + <pre> + private void fillData() { + // Get all of the notes from the database and create the item list + Cursor c = mDbHelper.fetchAllNotes(); + startManagingCursor(c); + + String[] from = new String[] { NotesDbAdapter.KEY_TITLE }; + int[] to = new int[] { R.id.text1 }; + + // Now create an array adapter and set it to display using our row + SimpleCursorAdapter notes = + new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to); + setListAdapter(notes); + }</pre> + + <p>Here's what we've done:</p> + <ol> + <li> + After obtaining the Cursor from <code>mDbHelper.fetchAllNotes()</code>, we + use an Activity method called + <code>startManagingCursor()</code> that allows Android to take care of the + Cursor lifecycle instead of us needing to worry about it. (We will cover the implications + of the lifecycle in exercise 3, but for now just know that this allows Android to do some + of our resource management work for us.)</li> + <li> + Then we create a string array in which we declare the column(s) we want + (just the title, in this case), and an int array that defines the View(s) + to which we'd like to bind the columns (these should be in order, respective to + the string array, but here we only have one for each).</li> + <li> + Next is the SimpleCursorAdapter instantiation. + Like many classes in Android, the SimpleCursorAdapter needs a Context in order to do its + work, so we pass in <code>this</code> for the context (since subclasses of Activity + implement Context). We pass the <code>notes_row</code> View we created as the receptacle + for the data, the Cursor we just created, and then our arrays.</li> + </ol> + <p> + In the future, remember that the mapping between the <strong>from</strong> columns and <strong>to</strong> resources + is done using the respective ordering of the two arrays. If we had more columns we wanted + to bind, and more Views to bind them in to, we would specify them in order, for example we + might use <code>{ NotesDbAdapter.KEY_TITLE, NotesDbAdapter.KEY_BODY }</code> and + <code>{ R.id.text1, R.id.text2 }</code> to bind two fields into the row (and we would also need + to define text2 in the notes_row.xml, for the body text). This is how you can bind multiple fields + into a single row (and get a custom row layout as well).</p> + <p> + If you get compiler errors about classes not being found, ctrl-shift-O or + (cmd-shift-O on the mac) to organize imports. + </p> + +<h2 style="clear:right;">Step 13</h2> + <p>Run it! + <ol> + <li> + Right click on the <code>Notepadv1</code> project.</li> + <li> + From the popup menu, select <strong>Run As</strong> > + <strong>Android Application</strong>.</li> + <li> + If you see a dialog come up, select Android Launcher as the way of running + the application (you can also use the link near the top of the dialog to + set this as your default for the workspace; this is recommended as it will + stop the plugin from asking you this every time).</li> + <li>Add new notes by hitting the menu button and selecting <em>Add + Item</em> from the menu.</li> + </ol> + +<h2 style="clear:right;">Solution and Next Steps</h2> + <p>You can see the solution to this class in <code>Notepadv1Solution</code> +from +the zip file to compare with your own.</p> + +<p>Once you are ready, move on to <a href="notepad-ex2.html">Tutorial +Exercise 2</a> to add the ability to create, edit and delete notes.</p> + |