Is it better to create new Activities or just create a different Layout and replace the existing layout?

Question

Since I am new to Android, I am now thinking on what is the correct way of doing things.

As it stands, the application I\'m writing has 4 different screens:

Answer 1

Not sure if this has been mentioned in any of the sub questions, but if you change activities pre-2.0 you cannot animate between them.

So if you have a loading screen and would like it to fade to a menu you have to use two views and switch between the two.