Question

I have a panel being changed by an action which swaps out it’s child panel with a new panel that has a different minimum Size. I need to inform my JSplitPane that one of it’s children panels has changed so I can call updateToPreferedSize method. Is there an event that is already fired which I should listen for? If not, how do I throw an event that the parent can catch to notify it?

Answer 1

The easiest way would be to fire a custom propertyChange event on the panel that swaps out the child, so that after it swaps out the child, it fires the event. Theres a good example here:
http://download.oracle.com/javase/tutorial/javabeans/properties/bound.html

Once you’ve done that, the JSplitpane can register a listener and listen for that property as described here:
http://download.oracle.com/javase/tutorial/uiswing/events/propertychangelistener.html

To sum it up, in the panel that swaps the child, you will need to initialize PropertyChangeSupport:

private final PropertyChangeSupport pcs = new PropertyChangeSupport( this );

Then when you swap out the panel:

//All code to swap out the panel goes here
this.pcs.firePropertyChange( "childUpdated", false, true );

And in the JSplitPane, you need something like this:

//...where initialization occurs:
...
amountField.addPropertyChangeListener("childUpdated",
                                      new ChildUpdateListener());
...
class ChildUpdateListener implements PropertyChangeListener {
    public void propertyChanged(PropertyChangeEvent e) {
        updateToPreferedSize();
    }
}