Custom Event Handling in Android

I currently have a Blossom class (which are flower petals that fall from the top of the screen). I want to be able to register when they collide with something (say, the basket that catches them). For an easier ex开发者_如何学编程ample, maybe we could discuss how I would register when they fall out of the screen (y value is > 430). How would I do this? I've been reading up a lot on custom event handlers, but I haven't been able to find anything that dumbs it down for me...which is what I need. I am trying to figure out the "Mr. Happy Object" example (Click Here) but I just can't work it out. Can anybody explain this with some rough examples, like, in very simplistic terms?