Swing Hacks

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Chapter 9, Drag-and-Drop

#69 Translucent Drag-and-Drop

HACK

H A C K

#69

Translucent Drag-and-Drop Hack #69

The Java implementation of drag-and-drop offers poor visual feedback. This

hack shows how to provide more information and a better-looking response

to the user.

A good way to create user-friendly interfaces is to provide the ability to drag-

and-drop almost anything from, within, and onto those interfaces. Mac OS X

is a perfect example of a good drag-and-drop use. Every time I try to drag

something to drop it onto something else, it just works. AWT, and there-

fore Swing, let applications implement drag-and-drop but lack something

Mac OS X already offers: really cool visual feedback to let the user know

what’s going on.

A Rather Boring Cursor

J2SE has offered drag-and-drop facilities since version 1.2. All the necessary

classes and interfaces can be found in the package

java.awt.dnd. Although

not very easy to use at first, this package provides powerful features you can

use to greatly improve the usability of your applications. Unfortunately, the

Java drag-and-drop framework offers little visual feedback. In fact, the only

feedback the user can get is a simple mouse cursor. For instance, you can

show that a drag-and-drop operation is in progress with the following line of

code:

dropTarget.setCursor(DragSource.DefaultMoveDrop);

Figure 9-6. Handling dropped images by supporting Pict format

Translucent Drag-and-Drop #69

Chapter 9, Drag-and-Drop

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Figure 9-7 shows what the visual feedback looks like on Windows.

Not only does this look bad, it also conveys very little information. Mac OS X

users are used to a much richer environment, and why should Windows or

Linux users expect less? As an example of what can be done, Safari—Mac

OS X’s default web browser—shows a translucent thumbnail of the picture

you are dragging. Figure 9-8 shows what this looks like in action.

Figure 9-7. Default drag-and-drop visual feedback on Windows

Figure 9-8. Mac OS X provides great looking visual feedback for drag-and-drop