You can use the getHeight() and getWidth() and make your application adapt to the screen size of the device it´s running on. This is how I do it, then of course there are other concerns as that some devices may not report the width and height correctly, in which case you could use hard coded values. To ease this even more, you could use a preprocessor to have one setup of code with preprocessor directives telling it for what platform the compiler should compile your game. I know there are some java preprocessors out there, but you could just as well use a C preprocessor in theory.
If you don't use any images, its possible to scale your game
width getHeight() and getWidth(), Once you start using images
its another story (since you can't scale images). I usally do
all paint (and help methods) in a View Class, so you just have
to do another View Class.
If you use images the only choice is to build different versions for each different screen type.
I prefer using final int constants for positioning images and define boundaries for each device. The game logic and paint method use these constants. The Ant with Antenna (build tool) can preprocess and build my apps for different devices in one go.