android - Setting up Alarm Manager is creating 2 Instances of my Main Activity

Question

I have 2 activities, a Main Activity and SetAlarm Activity. I call SetAlarm Activity from Main. When I set up the alarm I create an instance of my main. How do I set up the alarm without creating another instance of the Main or do I kill the main before setting up the alarm? Quite new to this. I have read several of the alarm manager examples, but they all seem to set up a new intent and I think this is what is creating my 2 instances. Is this how you set up the alarm. It does go off.

Here is how I call SetAlarm from the Main:

public void setAlarm(View view) {
    Intent intent = new Intent(this, SetAlarmActivity.class);
    startActivityForResult(intent, 2);  
} 

Here is how I set up the Alarm:

public void setUpAlarm() {
    if (VERBOSE) Log.v(TAG, "+++ IN setUpAlarm +++");                   
        PLAY_MUSIC = "Y";
        Intent intentAlarm = new Intent(this, MainActivity.class);
        intentAlarm.putExtra("playMusic",PLAY_MUSIC);
        intentAlarm.putExtra("mPos", mPos);
        intentAlarm.putExtra("result",ALARM_SET);
        setResult(RESULT_OK,intentAlarm);
        pIntent = PendingIntent.getActivity(this, 12345, 
                intentAlarm, PendingIntent.FLAG_UPDATE_CURRENT);
        AlarmManager am = (AlarmManager)(this.getSystemService( Context.ALARM_SERVICE ));
        am.set(AlarmManager.RTC_WAKEUP, calSet.getTimeInMillis(), pIntent );
    } // setAlarmPlaySong

I cut the alarm off in the main:

@Override
public void onResume() {
    if (VERBOSE) Log.v(TAG, "+++ IN onResume +++");
    super.onResume();  
    Intent intent = getIntent()
    if (intent.hasExtra("playMusic")  && intent.hasExtra("mPos")) {
   playMusicFlag = intent.getStringExtra("playMusic"); 
   mPos = intent.getIntExtra("mPos", 0);   
   if (playMusicFlag.equalsIgnoreCase("Y")) {
       if (VERBOSE) Log.v(TAG, "+++ playMusicFlag is SET+++");
           playSongs();
               showStopAlarmButton();
       } // if    
   }
}

Answer 1

if you want that your startActivity should not start multiple instances of alam activity you should go to your manifest and have to add an attribute named launchMode for your alarm activity and set it to SingleTop that will ensure that only one instance remains in the taskk back stack(plac where every activity resides in LIFO manner)