InactivityTimer.java

/**
 * Copyright (C) 2013 Eesti Vabariigi Valimiskomisjon 
 * (Estonian National Electoral Committee), www.vvk.ee
 *
 * Written in 2013 by AS Finestmedia, www.finestmedia.ee
 *
 * Vote-verification application for Estonian Internet voting system
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * This file incorporates work covered by the following copyright and  
 * permission notice:  
 * 
 * Copyright (C) 2008 ZXing authors
 * 
 * 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 ee.vvk.ivotingverification.qr;

import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;

/**
 * Finishes an activity after a period of inactivity if the device is on battery
 * power.
 */
public final class InactivityTimer {

	private static final int INACTIVITY_DELAY_SECONDS = 5 * 60;

	private final ScheduledExecutorService inactivityTimer = Executors
			.newSingleThreadScheduledExecutor(new DaemonThreadFactory());
	private final Activity activity;
	private ScheduledFuture<?> inactivityFuture = null;
	private final BroadcastReceiver powerStatusReceiver = new PowerStatusReceiver();

	public InactivityTimer(Activity activity) {
		this.activity = activity;
		onActivity();
	}

	public void onActivity() {
		cancel();
		if (!inactivityTimer.isShutdown()) {
			try {
				inactivityFuture = inactivityTimer.schedule(new FinishListener(
						activity), INACTIVITY_DELAY_SECONDS, TimeUnit.SECONDS);
			} catch (RejectedExecutionException ree) {
			}
		}
	}

	public void onPause() {
		cancel();
		try {
			activity.unregisterReceiver(powerStatusReceiver);
		} catch (Exception e) {
		}
	}

	public void onResume() {
		activity.registerReceiver(powerStatusReceiver, new IntentFilter(
				Intent.ACTION_BATTERY_CHANGED));
		onActivity();
	}

	private void cancel() {
		ScheduledFuture<?> future = inactivityFuture;
		if (future != null) {
			future.cancel(true);
			inactivityFuture = null;
		}
	}

	public void shutdown() {
		cancel();
		inactivityTimer.shutdown();
	}

	private static final class DaemonThreadFactory implements ThreadFactory {
		@Override
		public Thread newThread(Runnable runnable) {
			Thread thread = new Thread(runnable);
			thread.setDaemon(true);
			return thread;
		}
	}

	private final class PowerStatusReceiver extends BroadcastReceiver {
		@Override
		public void onReceive(Context context, Intent intent) {
			if (Intent.ACTION_BATTERY_CHANGED.equals(intent.getAction())) {
				int batteryPlugged = intent.getIntExtra("plugged", -1);
				if (batteryPlugged > 0) {
					InactivityTimer.this.cancel();
				}
			}
		}
	}
}