Guomato Guomato - 1 year ago 55
Android Question

Alarm Manager won't work when the app is killed in the background and device is locked

I have been stuck in this situation for a long time...

I want to use the alarm manager to show notification at the specific time, and now it worked in the situation listed below:

  1. when the app runs in the background, notification will be shown at the correct time, and no matter the device is locked or not.

  2. after the app has been killed in the background, i will still get correct notification when device is not locked, but things turn wrong when the device is locked, i can't receive any notification.

Here's the code, all the needed permission has been added into AndroidManifest.xml already:

public void onReceive(Context context, Intent intent) {

String action = intent.getAction();

Log.d(TAG, action); //when app is killed and device is locked, no info is shown at the logcat

if (ACTION_ALARM.equals(action)) {
Vibrator vibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
vibrator.vibrate(2 * 1000);

notify(context, "Jello!");


public static void alarm(Context context) {
AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(context, AlarmReceiver.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, 0);

alarmManager.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + 5 * 1000, pi);
} else {
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + 5 * 1000, pi);

private void notify(Context context, String msg) {
NotificationManager notificationManager = (NotificationManager)

PendingIntent contentIntent = PendingIntent.getActivity(context, 0,
new Intent(context, InfoActivity.class), 0);

Notification notification =
new NotificationCompat.Builder(context)
.setStyle(new NotificationCompat.BigTextStyle().bigText(msg))

notificationManager.notify(1, notification);

Permissions added:

<uses-permission android:name="android.permission.WAKE_LOCK"/>
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
<uses-permission android:name="android.permission.VIBRATE"/>

Answer Source

I had a similar issue one day and found a solution online, which was wakelocking the phone when the broadcastreceiver was called. So try creating this class, and calling MyWakeLock.acquire() when the broadcastreceiver gets called. You should also call MyWakeLock.release() when you are done executing whatever your alarm does.


import android.content.Context;
import android.os.PowerManager;

public abstract class MyWakeLock {
    private static PowerManager.WakeLock wakeLock;

    public static void acquire(Context c) {
        if (wakeLock != null) wakeLock.release();

        PowerManager pm = (PowerManager) c.getSystemService(Context.POWER_SERVICE);
        wakeLock = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK |
                PowerManager.ACQUIRE_CAUSES_WAKEUP |
                PowerManager.ON_AFTER_RELEASE, MainActivity.APP_TAG);

    public static void release() {
        if (wakeLock != null){
        wakeLock = null;