Asynchronously load data in an activity or fragment.

1. Loader
+Handaru Sakti

2. Intoduction
● Asynchronously load data in an activity or
fragment.
● Automatically reconnect to the last their cursor
when being recreated after a configuration
change (like screen flips). Thus, they don't need
to re-query their data.
● Introduced in Honeycomb, exist on Android
Support Package v-4.

3. Involved Classes and Interfaces
● LoaderManager
● LoaderManager.LoaderCallbacks
● Loader
● AsyncTaskLoader
● CursorLoader

4. Common Approach...
● LoaderManager to initialize a Loader. There is
only one LoaderManager per activity or
fragment, but a LoaderManager can have
multiple loaders.
● LoaderManager.LoaderCallbacks: a callback
interface for a client to interact with the
LoaderManager.
● Loader: an abstract class that performs
asynchronous loading of data. This is the base
class for a loader.

5. ...Common Approach
● AsyncTaskLoader: abstract loader that provides
an AsyncTask to do the work.
● A CursorLoader used to load data which
backed by a ContentProvider. Alternatively,
implement a subclass of Loader or
AsyncTaskLoader to load data from some other
source.
● A SimpleCursorAdapter used to display the
loader’s data.

6. Implementation
● Starting a Loader
– getLoaderManager().initLoader(0, null, this);
– Within Activity via onCreate() method.
– Within Fragment via onActivityCreated() method.
● Restarting a Loader
– getLoaderManager().restartLoader(0, null, this);

7. Using the LoaderManager Callbacks
LoaderManager.LoaderCallbacks includes these
methods:
– onCreateLoader() — Instantiate and return a new
Loader for the given ID.
– onLoadFinished() — Called when a previously
created Loader has finished its load.
– onLoaderReset() — Called when a previously
created Loader is being reset, thus making its data.

8. DEMO LoaderTest

9. References
● http://developer.android.com/guide/components
/loaders.html
● http://developer.android.com/reference/android/
content/Loader.html