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A comprehensive framework for caching and displaying data.
There is a newer version: 1.1.3
/* 
 * Copyright (C) 2014 Pivotal Software, Inc. 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.pivotal.arca.broadcaster;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class ArcaBroadcastManager {

	private static final int MSG_SEND_BROADCAST = 100;

	private static final Map> RECEIVERS = new HashMap>();
	private static final Map> ACTIONS = new HashMap>();

	private static final List BROADCASTS = new ArrayList();

	private static Context sContext;
	private static Handler sHandler;

	public static void initialize(final Context context, final BroadcastHandler handler) {
		sContext = context.getApplicationContext();
		sHandler = handler;
	}

	private static void initializeDefaultHandler(final Context context) {
		initialize(context, new BroadcastHandler(context.getMainLooper()));
	}

	// ====================================================

	public static synchronized void registerReceiver(final BroadcastReceiver receiver, final String action) {
		addToActions(receiver, action);
		addToReceivers(receiver, action);
	}

	public static synchronized void unregisterReceiver(final BroadcastReceiver receiver) {
		final Set actions = RECEIVERS.remove(receiver);
		removeReceiverFromActions(receiver, actions);
	}

	// ====================================================

	private static void addToReceivers(final BroadcastReceiver receiver, final String action) {
		Set actions = RECEIVERS.get(receiver);
		if (actions == null) {
			actions = new HashSet(1);
			RECEIVERS.put(receiver, actions);
		}
		actions.add(action);
	}

	private static void addToActions(final BroadcastReceiver receiver, final String action) {
		Set receivers = ACTIONS.get(action);
		if (receivers == null) {
			receivers = new HashSet(1);
			ACTIONS.put(action, receivers);
		}
		receivers.add(receiver);
	}

	private static void removeReceiverFromActions(final BroadcastReceiver receiver, final Set actions) {
		for (final String action : actions) {
			final Set receivers = ACTIONS.get(action);
			if (receivers != null) {
				receivers.remove(receiver);

				if (receivers.size() <= 0) {
					ACTIONS.remove(action);
				}
			}
		}
	}

	// ====================================================

	public static synchronized void sendBroadcast(final Context context, final Intent intent) {
		final String action = intent.getAction();
		final Set receivers = ACTIONS.get(action);

		if (receivers != null) {
			for (final BroadcastReceiver receiver : receivers) {
				BROADCASTS.add(new Broadcast(receiver, intent));
			}
			notifyMessageHandler(context);
		}
	}

	private static void notifyMessageHandler(final Context context) {
		if (sHandler == null) {
			initializeDefaultHandler(context);
		}
		if (!sHandler.hasMessages(MSG_SEND_BROADCAST)) {
			sHandler.sendEmptyMessage(MSG_SEND_BROADCAST);
		}
	}

	private static synchronized void sendAndClearBroadcasts() {
		for (final Broadcast broadcast : BROADCASTS) {
			broadcast.getReceiver().onReceive(sContext, broadcast.getIntent());
		}
		BROADCASTS.clear();
	}

	// ====================================================

	public static class BroadcastHandler extends Handler {

		public BroadcastHandler(final Looper looper) {
			super(looper);
		}

		@Override
		public void handleMessage(final Message msg) {
			if (msg.what == MSG_SEND_BROADCAST) {
				sendAndClearBroadcasts();
			}
		}
	}

	// ====================================================

	private static final class Broadcast {

		private final Intent mIntent;
		private final BroadcastReceiver mReceiver;

		public Broadcast(final BroadcastReceiver receiver, final Intent intent) {
			mReceiver = receiver;
			mIntent = intent;
		}

		public BroadcastReceiver getReceiver() {
			return mReceiver;
		}

		public Intent getIntent() {
			return mIntent;
		}
	}
}