session-android/src/org/thoughtcrime/securesms/util/RealtimeSleepTimer.java

package org.thoughtcrime.securesms.util;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Build;
import android.os.SystemClock;
import android.util.Log;

import org.whispersystems.signalservice.api.util.SleepTimer;

import java.util.concurrent.TimeUnit;

/**
 * A sleep timer that is based on elapsed realtime, so
 * that it works properly, even in low-power sleep modes.
 *
 */
public class RealtimeSleepTimer implements SleepTimer {
    private static final String TAG = RealtimeSleepTimer.class.getSimpleName();

    private final AlarmReceiver alarmReceiver;
    private final Context context;

    public RealtimeSleepTimer(Context context) {
        this.context = context;
        alarmReceiver = new RealtimeSleepTimer.AlarmReceiver();
    }

    @Override
    public void sleep(long millis) {
        context.registerReceiver(alarmReceiver,
                new IntentFilter(AlarmReceiver.WAKE_UP_THREAD_ACTION));

        final long startTime = System.currentTimeMillis();
        alarmReceiver.setAlarm(millis);

        while (System.currentTimeMillis() - startTime < millis) {
            try {
                synchronized (this) {
                    wait(millis - System.currentTimeMillis() + startTime);
                }
            } catch (InterruptedException e) {
                Log.w(TAG, e);
            }
        }

        context.unregisterReceiver(alarmReceiver);
    }

    private class AlarmReceiver extends BroadcastReceiver {
        private static final String WAKE_UP_THREAD_ACTION = "org.whispersystems.signalservice.api.util.RealtimeSleepTimer.AlarmReceiver.WAKE_UP_THREAD";

        private void setAlarm(long millis) {
            final Intent        intent        = new Intent(WAKE_UP_THREAD_ACTION);
            final PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
            final AlarmManager  alarmManager  = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);

            Log.w(TAG, "Setting alarm to wake up in " + millis + "ms.");

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                        SystemClock.elapsedRealtime() + millis,
                        pendingIntent);
            } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                alarmManager.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                        SystemClock.elapsedRealtime() + millis,
                        pendingIntent);
            } else {
                alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                        SystemClock.elapsedRealtime() + millis,
                        pendingIntent);
            }
        }

        @Override
        public void onReceive(Context context, Intent intent) {
            Log.w(TAG, "Waking up.");

            synchronized (RealtimeSleepTimer.this) {
                RealtimeSleepTimer.this.notifyAll();
            }
        }
    }
}