LoaderManager 사용 상세 정보(둘) - LoaderManager 이해

public class SampleActivity extends Activity implements LoaderManager.LoaderCallbacks<D> {  
  
  public Loader<D> onCreateLoader(int id, Bundle args) { ... }  
  
  public void onLoadFinished(Loader<D> loader, D data) { ... }  
  
  public void onLoaderReset(Loader<D> loader) { ... }  
  
  /* ... */  
}

public class SampleListActivity extends ListActivity implements  
    LoaderManager.LoaderCallbacks<Cursor> {  
  
  private static final String[] PROJECTION = new String[] { "_id", "text_column" };  
  
  // The loader's unique id. Loader ids are specific to the Activity or  
  // Fragment in which they reside.  
  private static final int LOADER_ID = 1;  
  
  // The callbacks through which we will interact with the LoaderManager.  
  private LoaderManager.LoaderCallbacks<Cursor> mCallbacks;  
  
  // The adapter that binds our data to the ListView  
  private SimpleCursorAdapter mAdapter;  
  
  @Override  
  public void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
  
    String[] dataColumns = { "text_column" };  
    int[] viewIDs = { R.id.text_view };  
  
    // Initialize the adapter. Note that we pass a 'null' Cursor as the  
    // third argument. We will pass the adapter a Cursor only when the  
    // data has finished loading for the first time (i.e. when the  
    // LoaderManager delivers the data to onLoadFinished). Also note  
    // that we have passed the '0' flag as the last argument. This  
    // prevents the adapter from registering a ContentObserver for the  
    // Cursor (the CursorLoader will do this for us!).  
    mAdapter = new SimpleCursorAdapter(this, R.layout.list_item,  
        null, dataColumns, viewIDs, 0);  
  
    // Associate the (now empty) adapter with the ListView.  
    setListAdapter(mAdapter);  
  
    // The Activity (which implements the LoaderCallbacks<Cursor>  
    // interface) is the callbacks object through which we will interact  
    // with the LoaderManager. The LoaderManager uses this object to  
    // instantiate the Loader and to notify the client when data is made  
    // available/unavailable.  
    mCallbacks = this;  
  
    // Initialize the Loader with id '1' and callbacks 'mCallbacks'.  
    // If the loader doesn't already exist, one is created. Otherwise,  
    // the already created Loader is reused. In either case, the  
    // LoaderManager will manage the Loader across the Activity/Fragment  
    // lifecycle, will receive any new loads once they have completed,  
    // and will report this new data back to the 'mCallbacks' object.  
    LoaderManager lm = getLoaderManager();  
    lm.initLoader(LOADER_ID, null, mCallbacks);  
  }  
  
  @Override  
  public Loader<Cursor> onCreateLoader(int id, Bundle args) {  
    // Create a new CursorLoader with the following query parameters.  
    return new CursorLoader(SampleListActivity.this, CONTENT_URI,  
        PROJECTION, null, null, null);  
  }  
  
  @Override  
  public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {  
    // A switch-case is useful when dealing with multiple Loaders/IDs  
    switch (loader.getId()) {  
      case LOADER_ID:  
        // The asynchronous load is complete and the data  
        // is now available for use. Only now can we associate  
        // the queried Cursor with the SimpleCursorAdapter.  
        mAdapter.swapCursor(cursor);  
        break;  
    }  
    // The listview now displays the queried data.  
  }  
  
  @Override  
  public void onLoaderReset(Loader<Cursor> loader) {  
    // For whatever reason, the Loader's data is now unavailable.  
    // Remove any references to the old data by replacing it with  
    // a null Cursor.  
    mAdapter.swapCursor(null);  
  }  
}