title: Alarm Manager doesn't work for me
body: <p>I'm trying to get the alarm to work, but it doesn't do anything, what do I'm mising? 
  My code is</p>
  
  <pre><code>        Calendar cal = Calendar.getInstance();
      Intent intent = new Intent(this, OnetimeAlarmReceiver.class);
      PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, 0);
  
      AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
      am.set(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis() + 3000, sender);
  </code></pre>
  
  <p>And my broadcast receiver looks like this</p>
  
  <pre><code>    public class OnetimeAlarmReceiver extends BroadcastReceiver {
  
      @Override
      public void onReceive(Context context, Intent intent) {
              Toast.makeText(context, "Alarm worked.", Toast.LENGTH_LONG).show();
      }
  }
  </code></pre>
  
  <p>Which is an inner class.</p>
  
  <p>What do I'm missing?</p>