91 lines
3.4 KiB
Plaintext
91 lines
3.4 KiB
Plaintext
page.title=Setting Up the Loader
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trainingnavtop=true
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startpage=true
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@jd:body
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<!-- This is the training bar -->
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<div id="tb-wrapper">
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<div id="tb">
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<h2>This lesson teaches you to</h2>
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<ol>
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<li>
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<a href="#AddExtensions">Extend an Activity</a>
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</li>
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<li>
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<a href="#GetLoader">Retrieve a LoaderManager</a>
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</li>
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<li>
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<a href="#InitializeLoader">Initialize the Loader Framework</a>
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</li>
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</ol>
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</div>
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</div>
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<p>
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You create a {@link android.support.v4.content.CursorLoader} within a
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<b>loader framework</b>. To set up the framework, you implement the
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{@link android.support.v4.app.LoaderManager.LoaderCallbacks LoaderCallbacks<Cursor>}
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as part of an {@link android.app.Activity}. In addition, to provide compatibility
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compatible with platform versions starting with Android 1.6, you must extend the
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{@link android.app.Activity} with the {@link android.support.v4.app.FragmentActivity} class.
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</p>
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<p class="note">
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<strong>Note:</strong> A {@link android.support.v4.app.Fragment} is not a prerequisite for
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{@link android.support.v4.content.CursorLoader}. As a convenience, the support library class
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{@link android.support.v4.app.FragmentActivity} contains the fragment and the loader frameworks,
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but they are completely independent of each other.
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</p>
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<p>
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Before you can use the loader framework, you need to initialize it. To do this, retrieve
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a {@link android.support.v4.app.LoaderManager} object and call its
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{@link android.support.v4.app.LoaderManager#initLoader initLoader()} method.
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</p>
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<p>
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If you do use one or more {@link android.support.v4.app.Fragment} objects in an
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{@link android.app.Activity}, the {@link android.support.v4.app.LoaderManager} you retrieve is
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available to all of them.
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</p>
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<h2 id="AddExtensions">Extend an Activity</h2>
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<p>
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To set up an {@link android.app.Activity} subclass to contain a
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{@link android.support.v4.content.CursorLoader}, extend the subclass with
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must extend {@link android.support.v4.app.FragmentActivity}, which provides the loader
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framework, and implement the {@link android.support.v4.app.LoaderManager.LoaderCallbacks
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LoaderCallbacks<Cursor>} interface, which specifies method signatures that the loader
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framework uses to interact with the {@link android.app.Activity}.
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</p>
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<p>
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For example:
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</p>
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<pre>
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public class DisplayActivity extends FragmentActivity
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implements LoaderManager.LoaderCallbacks<Cursor>
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</pre>
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<h2 id="GetLoader">Retrieve a LoaderManager</h2>
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<p>
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To get an instance {@link android.support.v4.app.LoaderManager} for use in your
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{@link android.app.Activity}, call
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{@link android.support.v4.app.FragmentActivity#getSupportLoaderManager
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FragmentActivity.getSupportLoaderManager()} at the beginning of the
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{@link android.app.Activity#onCreate onCreate()} method. For example:
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</p>
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<pre>
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private LoaderManager mLoaderManager;
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public void onCreate() {
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...
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mLoaderManager = this.getSupportLoaderManager();
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</pre>
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<h2 id="InitializeLoader">Initialize the Loader Framework</h2>
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<p>
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Once you have the {@link android.support.v4.app.LoaderManager} object, initialize
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it by calling {@link android.support.v4.app.LoaderManager#initLoader initLoader()}. For
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example:
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</p>
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<pre>
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// CursorLoader instance identifier
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public static final int URL_LOADER = 0;
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...
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// Initializes the CursorLoader
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getSupportLoaderManager().initLoader(URL_LOADER, null, this);
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</pre>
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