How do you start an Activity with AlarmManager in Android?

Question

I've poured through a dozen tutorials and forum answers about this problem, but still haven't been able to get some working code together. I'll try to keep the question straightforward:

How do you use AlarmManager (in the Android API) to start an Activity at a given time? Any solution to this problem will do.

My latest attempt to achieve this is below.

(Imports omitted. I expect MyActivity to start 3 seconds after the program is opened, which it doesn't. There are no error messages to speak of.)

public class AndroidTest2Activity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Context context = this;//.getApplicationContext();

        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); // CORRECT
        Intent intent = new Intent(context, myReceiver.class); // CORRECT
        PendingIntent pending = PendingIntent.getBroadcast( context, 0, intent, 0 ); // CORRECT
        manager.set( AlarmManager.RTC, System.currentTimeMillis() + 3000, pending ); // CORRECT

        setContentView(R.layout.main);
    }
}

public class myReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        Intent i=new Intent(context, myActivity.class);
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(i);
    }
}

public class myActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("", "Elusive success");
        setContentView(R.layout.main);
    }
}

Any advice would be appreciated.

Please note: I've got myReceiver in the manifest already

Answer 1

I had this problem too long ago to know which answer is correct, but thank you to everyone for their responses. I'm self-answering so the question isn't still open.

Answer 2

In case someone else stumbles upon this - here's some working code (Tested on 2.3.3 emulator):

public final void setAlarm(int seconds) {
    // create the pending intent
    Intent intent = new Intent(MainActivity.this, AlarmReceiver.class);
    // intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0,
            intent, 0);
    // get the alarm manager, and scedule an alarm that calls the receiver
    ((AlarmManager) getSystemService(ALARM_SERVICE)).set(
            AlarmManager.RTC, System.currentTimeMillis() + seconds
                    * 1000, pendingIntent);
    Toast.makeText(MainActivity.this, "Timer set to " + seconds + " seconds.",
            Toast.LENGTH_SHORT).show();
}

public static class AlarmReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
        Log.d("-", "Receiver3");
    }
}

AndroidManifest.xml:

    <receiver android:name="com.example.test.MainActivity$AlarmReceiver" >
    </receiver>

Issues with BenLambell's code :

• EITHER:
  • Move the receiver to it's own .java file or
  • make the inner class static - so it can be accessed from outside
• Receiver is not declared correctly in the manifest:
  • if it's an inner class in MainActivity use: <receiver android:name="package.name.MainActivity$AlarmReceiver" ></receiver>
  • if it's in a separate file: <receiver android:name="package.name.AlarmReceiver" ></receiver>

If your intention is to display a dialog in the receiver's onReceive (like me): that's not allowed - only activities can start dialogs. This can be achieved with a dialog activity.

You can directly call an activity with the AlarmManager:

Intent intent = new Intent(MainActivity.this, TriggeredActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(MainActivity.this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
((AlarmManager) getSystemService(ALARM_SERVICE)).set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + seconds * 1000, pendingIntent);

Answer 3

In my experience you can achieve this without broadcast receiver, just use PendingIntent.getActivity() instead of getbroadcast()

private void setReminder(){

AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
            Calendar startTime = Calendar.getInstance();
            startTime.add(Calendar.MINUTE, 1);
            Intent intent = new Intent(ReminderActivity.this, ReminderActivity.class);
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            PendingIntent pendingIntent = PendingIntent.getActivity(ReminderActivity.this, 1, intent, PendingIntent.FLAG_UPDATE_CURRENT);
            alarmManager.set(AlarmManager.RTC, startTime.getTimeInMillis(), pendingIntent);   
}

I've tested this code on android O but I'm not sure about other android versions please inform me if this doesn't work on any other android version.