Swing Hacks

Spin Open a Detail Pane #39

Chapter 5, Windows, Dialogs, and Frames

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203

HACK

The Invisible Man

This hack is fairly simple and relies on one fact: you can add a component to

a layout and alternately make it visible and invisible. Its position relative to

other components is preserved when it’s invisible, but it takes up no

onscreen space. So, a spin-open container consists of three components:

• The top component, which is always visible

• The spinner

• The bottom component, whose visibility can be set by clicking on the

spinner

The layout of these three is pretty straightforward, as seen in Example 5-6,

which lists the

MoreInfoPanel class but omits an inner class (for now).

Example 5-6. Laying out the three panel components

public class MoreInfoPanel extends JPanel {

public Component topComponent;

protected SpinWidget spinWidget;

public Component bottomComponent;

public static final int SPIN_WIDGET_HEIGHT = 14;

public MoreInfoPanel (Component tc, Component mic) {

topComponent = tc;

spinWidget = new SpinWidget( );

bottomComponent = mic;

doMyLayout( );

}

protected void doMyLayout( ) {

setLayout (new BoxLayout (this, BoxLayout.Y_AXIS));

add (topComponent);

add (spinWidget);

add (bottomComponent);

resetBottomVisibility( );

}

protected void resetBottomVisibility( ) {

if ((bottomComponent == null) ||

(spinWidget == null))

return;

bottomComponent.setVisible (spinWidget.isOpen( ));

revalidate( );

if ...