How do I draw on a Jpanel

Question

I've spent around 15 hours trying to work out how to draw something as simple as a line onto a JPanel!
I kind of understand about using paint, set color etc. if I was writing code in notepad I'm sure that it wouldn't be a problem but as I'm using the JDK SE form editor I'm very confused as to what should be done.
Basically i have a frame with 2 panels in gridLayout position and filled top to bottom left to right equally spaced.
I've added a button to the left panel. When this button is clicked I want to draw a line on the right panel. It's that simple! If I can do that then I can move on.
All the examples i've read don't show what to do when using the JDK SE form editor. Please can someone tell me exactly what to do...thanks

Answer 1

see if you can follow this
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Testing extends JFrame
  public Testing()
    setSize(400,300);
    setLocation(200,100);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    getContentPane().add(new DrawPanel());
    pack();
  public static void main(String[] args){new Testing().setVisible(true);}
class DrawPanel extends JPanel
  java.util.List points = new java.util.ArrayList();
  public DrawPanel()
    setPreferredSize(new Dimension(400,300));
    setBackground(Color.WHITE);
    addMouseListener(new MouseAdapter(){
      public void mousePressed(MouseEvent me){
        points = new java.util.ArrayList();
        points.add(me.getPoint());}});
    addMouseMotionListener(new MouseMotionListener(){
      public void mouseMoved(MouseEvent me){}
      public void mouseDragged(MouseEvent me){
        points.add(me.getPoint());
        DrawPanel.this.repaint();}});
  public void paintComponent(Graphics g)
    super.paintComponent(g);
    if(points.size() > 0)
      Point sPt = (Point)points.get(0);
      for(int x = 1, y = points.size(); x < y; x++)
        Point ePt = (Point)points.get(x);
        g.drawLine(sPt.x,sPt.y,ePt.x,ePt.y);
        sPt = ePt;
}if you want a bit of advice - dump the gui builder