(Android uses program analysis source code to simulate Letao, and uses client program source code to help you write other similar shopping applications. With this simple use example, you can understand some Android programming skills, such as: click event effect settings in the bottom menu bar, imitate the virtual progress bar when loading data from the server, and call the progress bar circularly through threads. The bottom menu module ListView listener Get the data of ListView. Inheritance activity classes can use this class's methods. This class provides the public methods used by activities in the whole project. All of this class belongs to public methods. This class can be used for integration, etc)