Load data asynchronously using CursorLoader

Android 3.0 introduces CursorLoader to load data asynchronously, in order to avoid blocking UI threads when querying databases synchronously. Prior to API 11, you can download the support library to enable previous systems to support this functionality.

Here's an example:

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
 }
}