Swing Hacks

Save Window Settings #37

Chapter 5, Windows, Dialogs, and Frames

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193

HACK

—Jonathan Simon

H A C K

#37

Save Window Settings Hack #37

Make sure your windows always show up right where you left them, even

after a program restarts, by saving the window position and size

automatically.

Swing is a rich toolkit that can be used to create many kinds of programs,

but there are certain features that virtually all applications need, like win-

dow settings and preferences. This hack shows how to automatically store

and retrieve window locations and dimensions in an existing program with-

out using custom

Frame subclasses, or even making many changes to your

existing code.

Saving the size and location of a window is actually pretty easy. You can just

store them in a file and retrieve them later. The difficulty is identifying each

window, and doing it in a way that’s as noninvasive as possible.

The Window Saver Class

The first step is to create a class that handles all of the work. Because man-

aging windows will be a global function of the entire program, start with a

simple singleton with a factory interface, as shown in Example 5-4.

JLabel dateLabel = new JLabel("12/31/99");

dateLabel.setHorizontalAlignment(SwingConstants.CENTER);

statusBar.addRightComponent(dateLabel, 30);

JLabel timeLabel = new JLabel("11:59 PM");

timeLabel.setHorizontalAlignment(SwingConstants.CENTER);

statusBar.addRightComponent(timeLabel, ...