Have a look at the SetGestureDetectorListener function where we are using the FromEventPattern method from the Observable framework. The function must be typed with a particular object (that is, MotionEvent) that contains an EventHandler property, in this case Touch. Every time a Touch event is fired, using the Window method, we wait 0.7 seconds before doing anything (this ensures that we only respond to the first event taken every period set in the Window method). Once this period is reached, SelectMany is called and the first Touch event is retrieved from the observable sequence via the Take method. Then we call Subscribe to assign the NotifyFocus method, and pass in the MotionEvent object taken from the SelectMany method.

To summarize, the FromEventPattern method is very useful for controlling multiple events and responding with specific actions. We have applied this technique with touch events because we want to make sure only one touch event is processed every...