Android AlarmManager晚上无法正常工作

Question

I'm having a problem with the Android AlarmManager. I want to show a notification everyday at 00:01 AM. When i test the notification during the day at something like 11:30 AM the notification does show up. But when i test it at 00:01 AM nothing shows up.

I think this has something to do with my phone being asleep after a few hours of no activity at 00:01 AM, but I am not sure. Does anybody have a solution for this? Thanks in advance.

MainActivity:

    Intent alarmIntent = new Intent(this, AlarmReceiver.class);

    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    AlarmManager manager = (AlarmManager) this.getSystemService(Context.ALARM_SERVICE);

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.set(Calendar.MINUTE, 1);

    Calendar now = Calendar.getInstance();
    now.setTimeInMillis(System.currentTimeMillis());

    if (calendar.before(now)) {
        calendar.add(Calendar.DAY_OF_MONTH, 1);

        manager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
                AlarmManager.INTERVAL_DAY, pendingIntent);
    } else {
        manager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
                AlarmManager.INTERVAL_DAY, pendingIntent);
    }

AlarmReceiver:

    private static int NOTIFICATION_ID;
    private NotificationManager notificationManager;
    private PendingIntent pendingIntent;

    Intent mIntent;

    @Override
    public void onReceive(Context context, Intent intent) {

    NOTIFICATION_ID = random.nextInt(9999 - 1000) + 1000;
    notificationManager = (NotificationManager) context.getSystemService(NOTIFICATION_SERVICE);
    mIntent = new Intent(context, BirthdayActivity.class);

    pendingIntent = PendingIntent.getActivity(context, NOTIFICATION_ID, mIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    NotificationCompat.Builder builder = new NotificationCompat.Builder(context);

    builder.setContentTitle("Name");
    builder.setContentIntent(pendingIntent);

    notificationManager = (NotificationManager) context.getSystemService(NOTIFICATION_SERVICE);
    notificationManager.notify(NOTIFICATION_ID, builder.build());
}

Manifest:

    <receiver android:name=".utils.AlarmReceiver" android:enabled="true">
    </receiver>

    <uses-permission android:name="com.android.alarm.permission.SET_ALARM"/>

Answer 1

I think everything is right with your code. You can check whether the alarm is set or not using this command on your android studio terminal. adb shell dumpsys alarms >dump.txt and then search for your package name in that file. This will confirm whether your alarm is set successfully or not.

Next you are using setRepeating which means system can adjust the delivery time. To deliver the alarm at the exact time use setExact here is a excerpt from the official android documentation:

Note: as of API 19, all repeating alarms are inexact. If your application needs precise delivery times then it must use one-time exact alarms, rescheduling each time as described above.

Answer 2

From the api docs:

Note: as of API 19, all repeating alarms are inexact. If your application needs precise delivery times then it must use one-time exact alarms, rescheduling each time as described above. Legacy applications whose targetSdkVersion is earlier than API 19 will continue to have all of their alarms, including repeating alarms, treated as exact.

https://developer.android.com/reference/android/app/AlarmManager.html#setRepeating(int, long, long, android.app.PendingIntent)

There are a few questions you should answer.

• Does this really need to be exact?

• If the user is sleeping can this wait until they wake up their phone?

Exact alarms are often discouraged as they disregard the state of the phone. For example, its not "nice" to the user to sync your app when they aren't even looking at their phone.

If you are connecting to a server and updating some data, I'd recommend a 'push' approach rather than a 'pull' approach.

Answer 3

They system only holds a wakelock while delivering the alarm notification to the AlarmReceiver . Unless there is some other reason for the device to stay awake, it is entirely possible that it will go back to sleep, before the Intent is delivered to the Activity.

Have a look at WakefulBroadcastReceiver