CursorLoader returns its query results to your implementation ofLoaderCallbacks.onLoadFinished(), in the form of a Cursor. In the callback, you can update your data display, do further processing on theCursor data, and so fort
When the loader framework detects changes to data associated with the query, it resets theCursorLoader, closes the current Cursor, and then invokes your implementation ofonLoaderReset(). Use this callback to delete references to the currentCursor; when the loader framework destroys the Cursor, you won't have outstanding references that cause memory leaks.
Handle Query Results
The following two snippets are an example of displaying the results of a query, using aListView backed by a SimpleCursorAdapter.
The first snippet shows the ListView and SimpleCursorAdapter:
// Gets a handle to the Android built-in ListView widget mListView = ((ListView) findViewById(android.R.id.list)); // Creates a CursorAdapter mAdapter = new SimpleCursorAdapter( this, // Current context R.layout.logitem, // View for each item in the list null, // Don't provide the cursor yet FROM_COLUMNS, // List of cursor columns to display TO_FIELDS, // List of TextViews in each line 0 // flags ); // Links the adapter to the ListView mListView.setAdapter(mAdapter);
The next snippet shows an implementation of onLoadFinished() that moves the query results in the returnedCursor to the SimpleCursorAdapter. Changing theCursor in the SimpleCursorAdapter triggers a refresh of theListView with the new data:
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) { /* * Move the results into the adapter. This * triggers the ListView to re-display. */ mAdapter.swapCursor(cursor); }
Handle a Loader Reset
The loader framework resets the CursorLoader whenever theCursor becomes invalid. This usually occurs because the data associated with theCursor has changed. Before re-running the query, the framework calls your implementation ofonLoaderReset(). In this callback, make sure to prevent memory leaks by deleting all references to the currentCursor. Once you return from onLoaderReset(), the loader framework re-runs the query.
For example:
public void onLoaderReset(Loader<Cursor> loader) { // Remove the reference to the current Cursor mAdapter.swapCursor(null); }
