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|Bruce Eckel's Thinking in Java||Contents | Prev | Next|
The original design goal of the graphical user interface (GUI) library in Java 1.0 was to allow the programmer to build a GUI that looks good on all platforms.
That goal was not achieved. Instead, the Java 1.0 Abstract Window Toolkit (AWT) produces a GUI that looks equally mediocre on all systems. In addition it’s restrictive: you can use only four fonts and you cannot access any of the more sophisticated GUI elements that exist in your operating system (OS). The Java 1.0 AWT programming model is also awkward and non-object-oriented.
Much of this situation has been improved with the Java 1.1 AWT event model, which takes a much clearer, object-oriented approach, along with the introduction of Java Beans, a component programming model that is particularly oriented toward the easy creation of visual programming environments. Java 1.2 finishes the transformation away from the old Java 1.0 AWT by adding the Java Foundation Classes (JFC), the GUI portion of which is called “Swing.” These are a rich set of easy-to-use, easy-to-understand Java Beans that can be dragged and dropped (as well as hand programmed) to create a GUI that you can (finally) be satisfied with. The “revision 3” rule of the software industry (a product isn’t good until revision 3) seems to hold true with programming languages as well.
One of Java’s primary design goals is to create applets, which are little programs that run inside a Web browser. Because they must be safe, applets are limited in what they can accomplish. However, they are a powerful tool in supporting client-side programming, a major issue for the Web.
Programming within an applet is so restrictive that it’s often referred to as being “inside the sandbox,” since you always have someone – the Java run-time security system – watching over you. Java 1.1 offers digital signing for applets so you can choose to allow trusted applets to have access to your machine. However, you can also step outside the sandbox and write regular applications, in which case you can access the other features of your OS. We’ve been writing regular applications all along in this book, but they’ve been console applications without any graphical components. The AWT can also be used to build GUI interfaces for regular applications.
In this chapter you’ll first learn the use of the original “old” AWT, which is still supported and used by many of the code examples that you will come across. Although it’s a bit painful to learn the old AWT, it’s necessary because you must read and maintain legacy code that uses the old AWT. Sometimes you’ll even need to write old AWT code to support environments that haven’t upgraded past Java 1.0. In the second part of the chapter you’ll learn about the structure of the “new” AWT in Java 1.1 and see how much better the event model is. (If you can, you should use the newest tools when you’re creating new programs.) Finally, you’ll learn about the new JFC/Swing components, which can be added to Java 1.1 as a library – this means you can use the library without requiring a full upgrade to Java 1.2.
Most of the examples will show the creation of applets, not only because it’s easier but also because that’s where the AWT’s primary usefulness might reside. In addition you’ll see how things are different when you want to create a regular application using the AWT, and how to create programs that are both applets and applications so they can be run either inside a browser or from the command line.
Please be aware that this is not a comprehensive glossary of all the methods for the described classes. This chapter will just get you started with the essentials. When you’re looking for more sophistication, make sure you go to your information browser to look for the classes and methods that will solve your problem. (If you’re using a development environment your information browser might be built in; if you’re using the Sun JDK then you use your Web browser and start in the java root directory.) Appendix F lists other resources for learning library details.