使用CursorLoader异步加载数据

public class ListViewLoader extends ListActivity
    implements LoaderManager.LoaderCallbacks<Cursor> {

  // This is the Adapter being used to display the list's data
  SimpleCursorAdapter mAdapter;

  // These are the Contacts rows that we will retrieve
  static final String[] PROJECTION = new String[] {ContactsContract.Data._ID,
      ContactsContract.Data.DISPLAY_NAME};

  // This is the select criteria
  static final String SELECTION = "((" + 
      ContactsContract.Data.DISPLAY_NAME + " NOTNULL) AND (" +
      ContactsContract.Data.DISPLAY_NAME + " != '' ))";

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Create a progress bar to display while the list loads
    ProgressBar progressBar = new ProgressBar(this);
    progressBar.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
        LayoutParams.WRAP_CONTENT, Gravity.CENTER));
    progressBar.setIndeterminate(true);
    getListView().setEmptyView(progressBar);

    // Must add the progress bar to the root of the layout
    ViewGroup root = (ViewGroup) findViewById(android.R.id.content);
    root.addView(progressBar);

    // For the cursor adapter, specify which columns go into which views
    String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME};
    int[] toViews = {android.R.id.text1}; // The TextView in simple_list_item_1

    // Create an empty adapter we will use to display the loaded data.
    // We pass null for the cursor, then update it in  Finished()
    mAdapter = new SimpleCursorAdapter(this, 
        android.R.layout.simple_list_item_1, null,
        fromColumns, toViews, 0);
    setListAdapter(mAdapter);

    // Prepare the loader. Either re-connect with an existing one,
    // or start a new one.
    getLoaderManager().initLoader(0, null, this);
  }

  // Called when a new Loader needs to be created
  public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // Now create and return a CursorLoader that will take care of
    // creating a Cursor for the data being displayed.
    return new CursorLoader(this, ContactsContract.Data.CONTENT_URI,
        PROJECTION, SELECTION, null, null);
  }

  // Called when a previously created loader has finished loading
  public void  Finished(Loader<Cursor> loader, Cursor data) {
    // Swap the new cursor in. (The  work will take care of closing the
    // old cursor once we return.)
    mAdapter.swapCursor(data);
  }

  // Called when a previously created loader is reset, making the data unavailable
  public void  erReset(Loader<Cursor> loader) {
    // This is called when the last Cursor provided to  Finished()
    // above is about to be closed. We need to make sure we are no
    // longer using it.
    mAdapter.swapCursor(null);
  }

  @Override 
  public void onListItemClick(ListView l, View v, int position, long id) {
    // Do something when a list item is clicked
  }
}