.drawLine on event (button click) Jpanel/Jbutton/JTabbedPane

I know how to do action listeners for button clicks in/on swing, but I have this class which does some stuff but I want it a function/event that when a button is clicked it runs a metho开发者_开发技巧d similiar to the PaintComponent below... (draws a line)

class CustomPanel extends JPanel {

    private int destx = 100;
    private int desty = 100;
    private int startx = 0;
    private int starty = 0;

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawLine(startx, starty, destx, desty);
    }

} 

How would I call this paintcomponent (Or a similar one which draws a line) from a action listener?

Here is my actionlistener: (Its on GUI.java while the code above is on CustomPanel.java)

public void actionPerformed(ActionEvent e)
    {
        if (e.getSource() == loginButton)
        {
            //Does other stuff but removed for simplifying
            CustomPanel cp = new CustomPanel();
        }
    }

Thanks alot,

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Your question didn't make sense to me in your last posting and it still doesn't make sense to me in this posting.

You still haven't posted a SSCCE that attempts to demonstrate what you want to do.

If you have a "login panel", typically that is done by creating a modal JDialog.

If you are trying to draw a diagonal across the top of all components in the frame, then you would need to use a Glass Pane or a Layered Pane.

Read the section from the Swing tutorial on How to Use Root Panes for examples and more detailed information.

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You need to add it to gui. Something like this:

 SwingUtilities.invokeLater(new Runnable() {
     public void run() {
         parentPanel.add(new CustomPanel());
         parentPanel.revalidate();
         parentPanel.repaint();
     }
 });

But if you only want to draw a line on the current container that's another thing...

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Simply adding your CustomPanel to any other JComponent and updating the UI should do the trick. Swing takes care of all the painting for you.

Here is a reslly useful guide to swing painting;
http://java.sun.com/products/jfc/tsc/articles/painting/#paint_process