BookmarkStatusLoader.java

package be.digitalia.fosdem.loaders;

import be.digitalia.fosdem.db.DatabaseManager;
import be.digitalia.fosdem.model.Event;
import be.digitalia.fosdem.utils.ArrayUtils;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v4.content.AsyncTaskLoader;
import android.support.v4.content.LocalBroadcastManager;

/**
 * This loader retrieves the bookmark status of an event from the database, then updates it in real time by listening to broadcasts.
 * 
 * @author Christophe Beyls
 * 
 */
public class BookmarkStatusLoader extends AsyncTaskLoader<Boolean> {

	final Event event;
	private Boolean isBookmarked;

	private final BroadcastReceiver addBookmarkReceiver = new BroadcastReceiver() {

		@Override
		public void onReceive(Context context, Intent intent) {
			if (event.getId() == intent.getLongExtra(DatabaseManager.EXTRA_EVENT_ID, -1L)) {
				updateBookmark(true);
			}
		}
	};

	private final BroadcastReceiver removeBookmarksReceiver = new BroadcastReceiver() {

		@Override
		public void onReceive(Context context, Intent intent) {
			long[] eventIds = intent.getLongArrayExtra(DatabaseManager.EXTRA_EVENT_IDS);
			if (ArrayUtils.indexOf(eventIds, event.getId()) != -1) {
				updateBookmark(false);
			}
		}
	};

	public BookmarkStatusLoader(Context context, Event event) {
		super(context);
		this.event = event;

		LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(getContext());
		lbm.registerReceiver(addBookmarkReceiver, new IntentFilter(DatabaseManager.ACTION_ADD_BOOKMARK));
		lbm.registerReceiver(removeBookmarksReceiver, new IntentFilter(DatabaseManager.ACTION_REMOVE_BOOKMARKS));
	}

	void updateBookmark(Boolean result) {
		if (isStarted()) {
			cancelLoad();
		}
		deliverResult(result);
	}

	@Override
	protected void onStartLoading() {
		if (isBookmarked != null) {
			// If we currently have a result available, deliver it
			// immediately.
			super.deliverResult(isBookmarked);
		} else {
			forceLoad();
		}
	}

	@Override
	protected void onStopLoading() {
		// Attempt to cancel the current load task if possible.
		cancelLoad();
	}

	@Override
	protected void onReset() {
		super.onReset();

		onStopLoading();
		isBookmarked = null;

		LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(getContext());
		lbm.unregisterReceiver(addBookmarkReceiver);
		lbm.unregisterReceiver(removeBookmarksReceiver);
	}

	@Override
	public void deliverResult(Boolean data) {
		isBookmarked = data;

		if (isStarted()) {
			// If the Loader is currently started, we can immediately
			// deliver its results.
			super.deliverResult(data);
		}
	}

	@Override
	public Boolean loadInBackground() {
		return DatabaseManager.getInstance().isBookmarked(event);
	}
}