Swing Hacks

210

|

Chapter 5, Windows, Dialogs, and Frames

#40 Minimize to a Mini-Frame

HACK

The code declares a MiniMizeHack class, which creates the UI and adds itself

as an

ActionListener to the Minimize and Restore menu items. The mouse

listener implementation is there to control the pop-up menu, but because

the

MiniMizeHack

class hasn’t been added as a listener to any components,

the pop up won’t do anything yet.

Minimize the Frame

The actionPerformed( ) method does the actual switching. This is the meat

of the hack. It tests if the bottom component is visible. If the component is

visible, then this method calls

switchToMini( )

and reshapes the frame to be

smaller. If the bottom component is not visible, then

actionPerformed( )

calls

switchToNormal( )

to reverse the changes:

public void actionPerformed(ActionEvent evt) {

if(bottom.isVisible( )) {

switchToMini( );

} else {

switchToNormal( );

}

}

The magic happens in the switchToMini( ) method. A big part of a mini win-

dow is that it doesn’t have any borders, or at the least it uses custom ones.

Swing does not let you turn off a frame’s borders and window decorations

after the frame has been shown on screen because it might have already allo-

cated immutable system resources. The only way around this limitation is to

seamlessly replace the old frame with a new one:

private Dimension normal_size;

public void switchToMini( ) {

// nuke the old frame and build a new one

Point location = frame.getLocation( );

normal_size = frame.getSize( );

frame.setVisible(false);

frame = new JFrame( );

frame.setUndecorated(true);

frame.getContentPane( ).add(panel);

The switchToMini( ) method starts by saving the current frame location and

size, and then hides the frame and replaces it with a new one. Now, it can

safely call

setUndecorated(true) on the frame. The frame.getContentPane( ).

add(panel)

line will add the main panel to the new frame. It is not necessary

to remove the panel from the old frame because Swing will take care of it

automatically. There is also no need to remove the menu bar because it had

never been added to the new frame.

Now, the code can hide the bottom component (the label representing the

extra clock configuration) and add the mouse listener to activate the pop up