When is a Swing component 'displayable'?

Question

Is there a way (e.g., via an event?) to determine when a Swing component becomes 'displayable' -- as per the Javadocs for Component.getGraphics?

The reason I'm trying to do this is so that I can then call getGraphics(), and pass that to my 'rendering strategy' for the component.

I've tried adding a ComponentListener, but componentShown doesn't seem to get called. Is there anything else I can try?

Thanks.

And additionally, is it OK to keep hold of the Graphics object I receive? Or is there potential for a new one to be created later in the lifetime of the Component? (e.g., after it is resized/hidden?)

Answer 1

Add a HierarchyListener

public class MyShowingListener {
private JComponent component;
public MyShowingListener(JComponent jc) { component=jc; }

public void hierarchyChanged(HierarchyEvent e) {
    if((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED)>0 && component.isShowing()) {
        System.out.println("Showing");
    }
}
}

JTable t = new JTable(...);
t.addHierarchyListener(new MyShowingListener(t));