Alarm Manager does not work in background on Andro

问题:

This is my Activity code,

Long time = new GregorianCalendar().getTimeInMillis()+20000;//Setting alarm after 20 sec
Intent intentAlarm = new Intent("alarm");
intentAlarm.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intentAlarm.putExtra("req_code",10);
PendingIntent pendingIntent = PendingIntent.getBroadcast(context,10, intentAlarm, PendingIntent.FLAG_UPDATE_CURRENT);
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarmManager.set(AlarmManager.RTC_WAKEUP, time, pendingIntent);

These are all the permissions that I have in my app,

  <uses-permission android:name="android.permission.VIBRATE" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
    <uses-permission android:name="android.permission.GET_ACCOUNTS"/>
    <uses-permission android:name="com.myapp.pack.permission.SET_ALARM"/>
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

This is my BroadcastReceiver code,

@Override
public void onReceive(Context context, Intent intent) {
        SharedPreferences sharedPreferences =
        context.getSharedPreferences( "mydata", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putBoolean("elligible",true);
        editor.apply();

    }

I have registered my BroadcastReceiver in the manifest,

 <receiver android:name="com.myapp.pack.AlarmReciever" android:enabled="true">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
            <action android:name="alarm" />
        </intent-filter>
    </receiver>

The above code successfully executes the BroadcastReceiver on pre-MarshMallow devices in the background ,but on a MarshMallow device ,the BroadcastReceiver does not get executed. Does anyone know what could be happening here? Thanks.

回答1:

There are a couple of things you can try which, when used in concert, should be able to cut through all of the idle/standby/doze modes (irrespective of OS version).

1. Use a WakefulBroadcastReceiver instead of an ordinary BroadcastReceiver. Make sure you include the WAKE_LOCK permission to use it correctly.

2. Use the setExactAndAllowWhileIdle() method (on API 23 & above) to schedule the Intent for the receiver:

if(Build.VERSION.SDK_INT < 23){
    if(Build.VERSION.SDK_INT >= 19){
        setExact(...);
    }
    else{
        set(...);
    }
}
else{
    setExactAndAllowWhileIdle(...);
}

References:

1. Alarm manager for background services.

2. A flowchart for background work, alarms, and your Android app.

回答2:

The reason can be Doze mode introduced in Android 6.0 Marshmallow. Use setAlarmclock() instead of set(). It's designed specifically for alarm clocks and may be able to cut through doze. There are a few adb commands you can use to manually put a phone into doze or app standby mode:

https://developer.android.com/preview/features/power-mgmt.html

If that isn't able to wake your app up, there's the surefire method setExactAndAllowWhileIdle() is designed to wake the phone from doze no matter what. Worst case scenario, you can wake your app up with this method and use the wakeup to schedule the next alarm.

Reference: How to make Alarm Manager work when Android 6.0 in Doze mode?