Body Collision Contact Point Monitoring

From: Himi "Android game programming from scratch" www.himigame.com

A collision listener Interface "Contactlistener" is provided in box2d, which uses an interface that requires rewriting its four abstract functions.

@Override public
	void Add (ContactPoint arg0) {
		//TODO auto-generated Method stub
		//Collision, response to this function
	when there is a new contact point }

	@Override public
	void persist (ContactPoint arg0) {
		//TODO auto-generated Method stub
		// Respond to this function when an existing contact point persists
	} @Override public
	void Remove (ContactPoint arg0) {
		//TODO auto-generated method Stub
		//Response to this function when the presence of a touch point is deleted
	}

	@Override public
	void result (Contactresult arg0) {
		//TODO auto-generated method Stub
		//per time step monitoring, if there is still a contact presence is responded to
	}

Through the instance of the parameter ContactPoint class, we can get the two body instances that collide with each other, get the body instance method as follows:

Body body1 = Arg0.shape1.getBody ();
Body body2 = Arg0.shape2.getBody ();

The application is as follows:

if (arg0.shape1.getBody () = = Bodyball && arg0.shape2.getBody () = = lostBody1) {
	gameislost = true;
} else if (arg0.shape1.getBody () = = Bodyball && arg0.shape2.getBody () = = LostBody2) {
	gameislost = true;
} else if (arg0.shape1.getBody () = = Bodyball && arg0.shape2.getBody () = = Winbody) {
	Gameiswin = true;
}

Finally, make sure to bind the listener to the physical world instance:

World.setcontactlistener (Contactlistener listener);