The Android environment adds yet another Graphical User Interface (GUI) toolkit to the Java ecosphere, joining AWT, Swing, SWT, and J2ME (leaving aside the web UI toolkits). If you've worked with any of these, the Android framework will look familiar. Like them, it is single-threaded, event-driven, and built on a library of nestable components.
The Android UI framework is, like the other UI frameworks, organized around the common Model-View-Controller pattern illustrated in Figure 10-1. It provides structure and tools for building a Controller that handles user input (like key presses and screen taps) and a View that renders graphical information to the screen.
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