Question about relative sizing on JPanels

Question

Hi,
My question is about relative sizing on components that are not drawn yet. For example I want to draw a JLabel on the 3rd quarter height of a JPanel. But JPanel's height is 0 as long as it is not drawn on the screen. Here is a sample code:
JPanel activityPnl = new JPanel();
private void buildActivityPnl(){
        //setting JPanel's look and feel
        activityPnl.setLayout(null);
        activityPnl.setBackground(Color.WHITE);
        int someValue = 30;  // I use this value to decide the width of my JPanel
        activityPnl.setPreferredSize(new Dimension(someValue, 80));
        //The JLabel's height is 1 pixel and its width is equal to the JPanel's width. I want to draw it on the 3/4 of the JPanel's height
        JLabel timeline = new JLabel();
        timeline.setOpaque(true);
        timeline.setBackground(Color.RED);
        timeline.setBounds(0, (activityPnl.getSize().height * 75) / 100 , someValue , 1);
        activityPnl.add(timeline);
    }Thanks a lot for your help
SD
Edited by: swingDeveloper on Feb 24, 2010 11:41 PM

Answer 1

And use a layout manager. It can adjust automatically for a change in the frame size.
Read the Swing tutorial on Using Layout Managers for examples of the different layout managers.