How to set an alarm to be scheduled at an exact time after all the newest restrictions on Android?

Question

Found a weird workaround (sample here) that seems to work for all versions, including even Android R:

Have the permission SAW permission declared in the manifest:

      <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

On Android R you will have to also have it granted. On before, doesn’t seem like it’s needed to be granted, just declared. Not sure why this changed on R, but I can say that SAW could be required as a possible solution to start things in the background, as written here for Android 10.

EDIT: Here is a guide on how to request it.

Have a service that will detect when the tasks was removed, and when it does, open a fake Activity that all it does is to close itself:

class OnTaskRemovedDetectorService : Service() {
    override fun onBind(intent: Intent?) = null

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int) = START_STICKY

    override fun onTaskRemoved(rootIntent: Intent?) {
        super.onTaskRemoved(rootIntent)
        Log.e("AppLog", "onTaskRemoved")
        applicationContext.startActivity(Intent(this, FakeActivity::class.java).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK))
        stopSelf()
    }

}

FakeActivity.kt

class FakeActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d("AppLog", "FakeActivity")
        finish()
    }
}

You can also make this Activity almost invisible to the user using this theme:

    <style name="AppTheme.Translucent" parent="@style/Theme.AppCompat.NoActionBar">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:colorBackgroundCacheHint">@null</item>
        <item name="android:windowIsTranslucent">true</item>
    </style>

Sadly, this is a weird workaround. I hope to find a nicer workaround to this.

The restriction talks about starting Activity, so my current idea is that maybe if I start a foreground service for a split of a second it will also help, and for this I won’t even need SAW permission.

EDIT: OK I tried with a foreground service (sample here), and it didn’t work. No idea why an Activity is working but not a service. I even tried to re-schedule the alarm there and tried to let the service stay for a bit, even after re-schedule. Also tried a normal service but of course it closed right away, as the task was removed, and it didn’t work at all (even if I created a thread to run in the background).

Another possible solution that I didn’t try is to have a foreground service forever, or at least till the task is removed, but this is a bit weird and I don’t see the apps I’ve mentioned using it.

EDIT: tried to have a foreground service running before removal of the app’s task, and for a bit afterwards, and the alarm still worked. Also tried to have this service to be the one in charge of task-removed event, and to close itself right away when it occurs, and it still worked (sample here). The advantage of this workaround is that you don’t have to have the SAW permission at all. The disadvantage is that you have a service with a notification while the app is already visible to the user. I wonder if it’s possible to hide the notification while the app is already in the foreground via the Activity.

EDIT: Seems it’s a bug on Android Studio (reported here, including videos comparing versions).
When you launch the app from the problematic version I tried, it could cause the alarms to be cleared.

If you launch the app from the launcher, it works fine.

This is the current code to set the alarm:

        val timeToTrigger = System.currentTimeMillis() + 10 * 1000
        val pendingShowList = PendingIntent.getActivity(this, 1, Intent(this, SomeActivity::class.java), PendingIntent.FLAG_UPDATE_CURRENT)
        val pendingIntent = PendingIntent.getBroadcast(this, 1, Intent(this, AlarmReceiver::class.java), PendingIntent.FLAG_UPDATE_CURRENT)
        manager.setAlarmClock(AlarmManager.AlarmClockInfo(timeToTrigger, pendingShowList), pendingIntent)

I don’t even have to use “pendingShowList”. Using null is also ok.

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