1 page.title=Setting Up the Loader 2 trainingnavtop=true 3 startpage=true 4 5 @jd:body 6 7 <!-- This is the training bar --> 8 <div id="tb-wrapper"> 9 <div id="tb"> 10 <h2>This lesson teaches you to</h2> 11 <ol> 12 <li> 13 <a href="#AddExtensions">Extend an Activity</a> 14 </li> 15 <li> 16 <a href="#GetLoader">Retrieve a LoaderManager</a> 17 </li> 18 <li> 19 <a href="#InitializeLoader">Initialize the Loader Framework</a> 20 </li> 21 </ol> 22 </div> 23 </div> 24 <p> 25 You create a {@link android.support.v4.content.CursorLoader} within a 26 <b>loader framework</b>. To set up the framework, you implement the 27 {@link android.support.v4.app.LoaderManager.LoaderCallbacks LoaderCallbacks<Cursor>} 28 as part of an {@link android.app.Activity}. In addition, to provide compatibility 29 compatible with platform versions starting with Android 1.6, you must extend the 30 {@link android.app.Activity} with the {@link android.support.v4.app.FragmentActivity} class. 31 </p> 32 <p class="note"> 33 <strong>Note:</strong> A {@link android.support.v4.app.Fragment} is not a prerequisite for 34 {@link android.support.v4.content.CursorLoader}. As a convenience, the support library class 35 {@link android.support.v4.app.FragmentActivity} contains the fragment and the loader frameworks, 36 but they are completely independent of each other. 37 </p> 38 <p> 39 Before you can use the loader framework, you need to initialize it. To do this, retrieve 40 a {@link android.support.v4.app.LoaderManager} object and call its 41 {@link android.support.v4.app.LoaderManager#initLoader initLoader()} method. 42 </p> 43 <p> 44 If you do use one or more {@link android.support.v4.app.Fragment} objects in an 45 {@link android.app.Activity}, the {@link android.support.v4.app.LoaderManager} you retrieve is 46 available to all of them. 47 </p> 48 <h2 id="AddExtensions">Extend an Activity</h2> 49 <p> 50 To set up an {@link android.app.Activity} subclass to contain a 51 {@link android.support.v4.content.CursorLoader}, extend the subclass with 52 must extend {@link android.support.v4.app.FragmentActivity}, which provides the loader 53 framework, and implement the {@link android.support.v4.app.LoaderManager.LoaderCallbacks 54 LoaderCallbacks<Cursor>} interface, which specifies method signatures that the loader 55 framework uses to interact with the {@link android.app.Activity}. 56 </p> 57 <p> 58 For example: 59 </p> 60 <pre> 61 public class DisplayActivity extends FragmentActivity 62 implements LoaderManager.LoaderCallbacks<Cursor> 63 </pre> 64 <h2 id="GetLoader">Retrieve a LoaderManager</h2> 65 <p> 66 To get an instance {@link android.support.v4.app.LoaderManager} for use in your 67 {@link android.app.Activity}, call 68 {@link android.support.v4.app.FragmentActivity#getSupportLoaderManager 69 FragmentActivity.getSupportLoaderManager()} at the beginning of the 70 {@link android.app.Activity#onCreate onCreate()} method. For example: 71 </p> 72 <pre> 73 private LoaderManager mLoaderManager; 74 public void onCreate() { 75 ... 76 mLoaderManager = this.getSupportLoaderManager(); 77 </pre> 78 <h2 id="InitializeLoader">Initialize the Loader Framework</h2> 79 <p> 80 Once you have the {@link android.support.v4.app.LoaderManager} object, initialize 81 it by calling {@link android.support.v4.app.LoaderManager#initLoader initLoader()}. For 82 example: 83 </p> 84 <pre> 85 // CursorLoader instance identifier 86 public static final int URL_LOADER = 0; 87 ... 88 // Initializes the CursorLoader 89 getSupportLoaderManager().initLoader(URL_LOADER, null, this); 90 </pre> 91
