Chapter 17: Windows, Frames, Dialogs and Menus

The java.awt.Window class and its subclasses let you create free-standing windows. Stand-alone windows can also be used to build applications that use the AWT instead of the command-line or to provide additional space for applets. A Window is a subclass of java.awt.Container that is independent of other Containers. That is, a Window is not itself contained. Since Window is a subclass of java.awt.Container you can add Components like Buttons and TextFields to Windows. You can arrange the Components you add with a LayoutManager. You can draw directly into a Window in a paint method. Everything you did in an applet panel in the last five chapters can also be done in a Window.

Normally you won't use the Window class directly but will access one of its subclasses, either java.awt.Frame or java.awt.Dialog depending on your need. A Frame is what most people think of as a window in their native environment. It can have a menu bar; it can be independently moved and resized; and it will hang around on the screen as long as the user is interested in the content of the window.

A Dialog will not have a menu bar. It can be moved but often can't be resized. Its purpose is to get some particular information from the user (input) or to impart some particularly important information to the user (output). It is normally visible on the screen only until it gets the input or receives acknowledgement from the user about its output.

In this chapter you learn

How to use Frames
How to create Dialogs
What a modal Dialog is
How to write applications that use the AWT
What the Window Events are
How to add Menus to your Windows

The Examples

Example 17.1: Window Tester
The example in the book is an uncloseable window. You may wish to look at a slightly better example that lets the window be closed.
Example 17.2: Dialog Tester
Warning: This example may force you to quit Netscape. You can look at a somewhat more complex but less hostile applet if you wish.
Example 17.3 and 17.4 An Alert Dialog and a Simple Applet to Demonstrate the Alert Dialog
Example 17.5: Menu Tester
Example 17.6: Active Menus Warning: This applet may crash Netscape 3.0 for the Mac and possibly other versions. It works properly in Sun's applet viewer on the Mac.