In iOS, we've the property numberOfTouchesRequired in UIGestureRecognizer class.
Its meaning is: the number of fingers required to tap for the gesture to be recognized.
@property(nonatomic) NSUInteger numberOfTouchesRequired
It works a bit differently in Android, but you can get the same feature.
You just need to override
There, you will be able to manipulate the event variable that contains among other things the number of fingers on the screen (