How can I change the vibration pattern during an incoming call on my Android phone?

[AC Question]

Change vibration pattern during an incoming call on my android phone

I am trying to change the vibration pattern of my phone on receiving an incoming call. I am able to vibrate my device in case of no incoming call.

Vibrator v = (Vibrator) this.context.getSystemService(Context.VIBRATOR_SERVICE);
// Vibrate for 500 milliseconds
v.vibrate(500);

But, when I receive an incoming call, my app unexpectedly stops.