How to Draw in Java

EE3206/EE5805 Java Programming and Applications

notes from Liang(2009), p.478

How to draw in Java:

1. create a class that extends JPanel

2. override paintComponent()

The paintComponent() is automatically invoked to paint graphics when the component is first displayed or whenever the component needs to be redisplayed.

import javax.swing.*;
import java.awt.Graphics;
import java.awt.*;


public class TestDrawPanel extends JFrame {
    
    public TestDrawPanel()
    {
        JPanel dp = new DrawPanel();
        dp.setBackground(Color.ORANGE);
        
        add(dp);
          // 3. add JPanel to the JFrame
    }

    public static void main(String[] args)
    {
        TestDrawPanel tdp = new TestDrawPanel();

        tdp.setTitle("TestDrawPanel");
        tdp.setSize(300,200);
        tdp.setLocationRelativeTo(null);
        tdp.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        tdp.setVisible(true);

    }

class DrawPanel extends JPanel
{
    // to draw, 1. create a class that extends JPanel
    protected  void paintComponent(Graphics g)
    {
       // 2. override the paintComponent()
        //
        super.paintComponent(g);

        g.setColor(Color.RED);
        g.drawLine(10,10, 70, 70);
        g.drawRect(30,50 ,150, 100);
    }
}


}