We don’t teach you Java in this book, but in this chapter we’ll help you understand the special use of Java within Android. Many people can benefit from this chapter: students who have learned some Java but haven’t yet stumbled over the real-life programming dilemmas it presents, programmers from other mobile environments who have used other versions of Java but need to relearn some aspects of the language in the context of Android programming, and Java programmers in general who are new to Android’s particular conventions and requirements.
If you find this chapter too fast-paced, pick up an introductory book on Java. If you follow along all right but a particular concept described in this chapter remains unclear to you, you might refer to the Java tutorial at http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/index.html.
Android is already the most widely used way of creating interactive clients using the Java language. Although there have been several other user interface class libraries for Java (AWT, SWT, Swing, J2ME Canvas, and so on), none of them has been as widely accepted as Android. For any Java programmer, the Android UI is worth learning just to understand what the future of Java UIs might look like.
The Android toolkit doesn’t gratuitously bend Java in unfamiliar directions. The mobile environment is simply different. There is a much wider variety of display sizes and shapes; there is no mouse (though ...