Reference trouble

Question

I want to pass a reference to a method in a separate public class. I have an actionEvent in my main class in a file main.java:
private void outlineActionPerformed(java.awt.event.ActionEvent evt) {                                       
        anotherclass.outline(Graphics2D g2);
    }I want this to reference a method in anotherclass.java:
static void outline(Graphics2D g2) {
    }The arguments are initialised in anotherclass like so:
public void paintComponent(Graphics g) {
  // Clear off-screen bitmap
  super.paintComponent(g);
  // Cast Graphics to Graphics2D
  Graphics2D g2 = (Graphics2D)g;
  g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
  }What gives?

Answer 1

I'm guessing you want to have a reference to the Graphics object used by the paintComponent method in the outlineActionPerformed method? Possibly so that you can do some painting in the actionPerformed method instead of the paintComponent method?
If so, that's probably a bad idea. A better way to do it would be to set some state data in the actionPerformed method, which the paintComponent method uses to paint the component. The paintComponent method could be using a new Graphics object each time it's called for all you know, so if you stored a reference to it, you could end up drawing on a Graphics that isn't being painted to the screen anymore.
If you want to call the outline method to delegate some painting, then call it from the paintComponent method, and pass it the Graphics that gets passed to paintComponent as a parameter. The outline method probably shouldn't be static either, but without seeing the rest of the design, I can't be sure.
private void outlineActionPerformed(java.awt.event.ActionEvent evt) {                                       
        someStuffToBeDrawn = whatever;
static void outline(Graphics2D g2) {
        // draw some stuff on g2 here maybe?
public void paintComponent(Graphics g) {
  // Clear off-screen bitmap
  super.paintComponent(g);
  // Cast Graphics to Graphics2D
  Graphics2D g2 = (Graphics2D)g;
  g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
   // do some painting based on someStuffToBeDrawn
   // maybe call outline(g2) so it can do some other painting?
  }