Question

I am writing a basic game engine and have an abstract class that represents any object that can be drawn in the 3D world, however inside this class is an abstract method Render() which I would like called automatically by the engine on each draw phase. How could I implement this so that every class extending from my abstract class will automatically have Render() called?

I am using java, android sdk 2.2, and opengl es.

Answer 1

You can register every object which can be rendered to a class which will call render() on all your objects.

For example :

public class Registry{
    private static Collection<RenderedObject> register = new ArrayList<RenderedObject>();

    public static void add(RenderedObject obj){
        register.add(obj);
    }

    public static void renderAll(){
        for(RenderedObject obj : register){
            obj.render();
        }
    }
}

And you can register your objects into the registry within the constructor of your RenderedObject.