Refactoring MainActivity to PongActivity

I think MainActivity is a bit vague as it was in the Sub Hunter project, but we won't refactor MainActivity to Pong or PongGame because now that we are dividing our game up into multiple classes, Pong or PongGame seem a bit too grand. In this project, our Activity-based class will not be the entire game. It will be a mere Activity, an entry point to our game engine and all the game objects. Let's refactor MainActivity to PongActivity.

In the project panel, right-click the MainActivity file and select Refactor | Rename. In the pop-up window, change MainActivity to PongActivity. Leave all the other options at the defaults and left-click the Refactor button.

Notice the filename in the project panel has changed as expected but also multiple occurrences of MainActivity have been changed to PongActivity in the AndroidManifest.xml file, as well as an instance in the PongActivity.java file. First, we will make sure the game is played...