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AWT Components
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| Supplements AWT Components Button Demo 1 Canvas Demo 2 AWT GUI Demo Demo 3 Swing Dialogs JOptionPane Dialog Demo 1 JDialog Demo 2 UI Enhancement: P1 Demo 1 Demo 2 Demo 3 UI Enhancement: P2 Demo 1 |
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The basic AWT framework offers a number of user interface components. As discussed in Chapter 6: Java : AWT, the AWT components, are closely bound to their peers in the windowing system on the local platform. These heavyweight components thus generally take a lowest common denominator approach for the sake of portability. However, in some cases, such as on a platform with limited memory resources, you may want to avoid using the Swing components. Here we look at some of the heavyweight AWT components. The Component class extends Object and is the base class for the AWT (as well as for Swing components). All the visible elements of an applet or application are components of one kind or another. The Component class has a very large number of methods for dealing with all aspects of the appearance, position, size, and other properties of components. For example, the paint() and getSize() methods, which we used in several examples, come from the Component class (the Applet class inherits Component). See the Java API specification page for the Component class to become familiar with all that it does. The Container class objects hold groups of components. The Panel class is a commonly used container. In fact, the Applet class inherits the Panel class: Object <- Component <- Container <- Panel <- Applet The add(Component a) method puts the component into the container. Since containers themselves are components, they can in turn be added to other containers. The arrangement of components within a container is determined by the layout manager to be discuss later. The default layout manager for Panel is the FlowLayout which places the components left to right, top to bottom In this section we provide a demonstration program to illustrate the basics of using the Button and Label components. We also use a Canvas as a drawing surface in another demonstrator. Other AWT heavyweight components include (corresponding Swing component given in parentheses):
The GUI example program uses several of these components to demonstrate building an interface in the AWT framework.
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