AlarmManager not starting on android

Question

I want to set an alarm on android but its not working, here is my code.. I used the pending intent to start the alarm at a specific time, but when I run the app on my device it doesn't starts.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Intent alarmIntent = new Intent(MainActivity.this, AlarmReceiver.class);
    pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, alarmIntent, 0);

    findViewById(R.id.startAlarm).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);


            Calendar calendar = Calendar.getInstance();
            calendar.setTimeInMillis(System.currentTimeMillis());
            calendar.set(Calendar.HOUR_OF_DAY, 16);
            calendar.set(Calendar.MINUTE, 39);

            /* Repeating on every 20 minutes interval */
            manager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
                    1000 * 60 * 20, pendingIntent);

            Toast.makeText(MainActivity.this, "Alarm Set", Toast.LENGTH_SHORT).show();
        }
    });

    findViewById(R.id.stopAlarm).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
            manager.cancel(pendingIntent);
            Toast.makeText(MainActivity.this, "Alarm Canceled", Toast.LENGTH_SHORT).show();
        }
    });
}

I am new to android, so please help. And here is my receiver class

public class AlarmReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        // For our recurring task, we'll just display a message
        Toast.makeText(context, "I'm running", Toast.LENGTH_SHORT).show();
    }
}

Answer 1

Have you declared your receiver in the manifest?

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