[Android Pro] 使用CursorLoader异步加载数据 from 3.0

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 onLoadFinished()
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 onLoadFinished(Loader<Cursor> loader, Cursor data) {
// Swap the new cursor in. (The framework 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 onLoaderReset(Loader<Cursor> loader) {
// This is called when the last Cursor provided to onLoadFinished()
// 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
}
}