Wizard API updated!
Tim Boudreau has released a new version of the Swing Wizard library (version 0.997) that fixes the WizardException bug reported in JavaWorld's recent Open Source Java Project profile. The article's examples have been reworked to test out the new, improved WizardException. Thanks, Tim, for this helpful fix!
Open Source Java Projects: The Wizard API

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Create a scrollable virtual desktop in Swing

Enhance your Java GUIs with the JScrollableDesktopPane class

By Tom Tessier, JavaWorld.com, 11/30/01

The JDesktopPane class, first introduced in JDK 1.2 as a subsidiary to Swing's GUI component series, lets you create a virtual desktop or Multiple Document Interface (MDI) in Java applications. JInternalFrame's various child windows or internal frames populate this desktop, and because those frames are internal, they are clipped at the boundary of the JDesktopPane container class (as opposed to JFrame's external frames, which are painted without regard to container boundaries).

This clipping, demonstrated in Figure 1, exemplifies one of JDesktopPane's inherent limitations: a user cannot view an internal frame's hidden portion without dragging the frame back within the virtual desktop boundary, or resizing the JDesktopPane container itself. Needless to say, such actions are not conducive to navigability and usability.

Figure 1. Internal frame clipped by the virtual desktop. Click on thumbnail to view full-size image.

JDesktopPane's second limitation is that it doesn't provide a simple method to switch between internal frames; instead, you must click upon the frame title bar. Should internal frames obscure one another, the user must drag each frame aside before the next one becomes accessible. This work becomes tedious if several internal frames overlap, as is possible in any MDI environment.

Introducing JScrollableDesktopPane

The JScrollableDesktopPane class presented in this article offers a solution to the aforementioned clipping and overlap problems, and mimics the interface of the original JDesktopPane class in order to easily upgrade your application. Figure 2 depicts the scrollable desktop pane in action. As Figure 2 shows, JScrollableDesktopPane involves three main subcomponents: a virtual desktop, a toolbar, and a menu.

Figure 2. The JScrollableDesktopPane class in action. Click on thumbnail to view full-size image.

The virtual desktop comprises the main display area. When internal frames are positioned outside the virtual desktop's boundary, scroll bars update to provide access to the cropped internal frames, solving the clipping problem.

A toolbar provides a lengthwise set of toggle buttons above the virtual desktop, with each button mapped to a corresponding internal frame. The toolbar contents automatically size to fit as you add or remove buttons. When you click a button, the associated frame centers upon the virtual desktop and positions atop all other internal frames, solving the accessibility problem.

You may register a menu bar with JScrollableDesktopPane so that your application can offer an alternative solution to the accessibility problem. Upon registration, a Window menu is added to the main application's menu bar. This menu contains Tile, Cascade, Auto, and Close options along with a set of radio buttons that serve as dynamic shortcuts to the internal frames. Tile saturates the desktop with a tiled version of all internal frames, as shown in Figure 3.

Figure 3. Internal frames displayed in Tile mode. Click on thumbnail to view full-size image.

Cascade positions each internal frame in diagonal succession, as shown in Figure 4.

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