Windowed, threaded, double-buffered JFrame with Graphics2D text.

eastward-sphere

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package lab;

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


/**
 * Moment of truth: threaded display to move a ball around
 * Will it appear double-buffered ?
 * @author Core ideas from Brackeen, Holder & Bell
 */
public class Bounce extends JFrame implements Runnable {
    
    public static void main(String[] args) { 
        
        Bounce b = new Bounce(500,500);
        
        new Thread(b).start();
    }
    
    private boolean running = true;
    private Image offscreenImage;
    private Graphics offscr;
    private int width, height;      // bounds
    
    public Bounce(int width, int height) { 
        super();
        
        this.width = width;
        this.height = height;
        
        setPreferredSize(new Dimension(width, height));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);
        pack();
        setVisible(true);
    }
    
    public void run() { 
        while (running) { 
            try {                
                repaint();
                
                System.out.println("ball moved to (" + x + "," + y + ")");
                
                try { 
                    Thread.sleep(1000/30);
                } catch (InterruptedException e) { 
                    
                }
            } finally { 
                
            }
        }
    }
    
    float x = 0;
    float y = 100;
    float dx = 1;
    float dy = 0;   // purely eastward movement
    
    public void paint(Graphics g) { 
        if (offscr == null) {
            offscreenImage = createImage(getWidth(), getHeight());
            offscr = offscreenImage.getGraphics();
        }
        // draw to offscr context here
        // Draw checkerboard background
        int x2 = width >> 1;
        int y2 = height >> 1;
        offscr.setColor(Color.gray);
        offscr.fillRect(0, 0, x2, y2);
        offscr.fillRect(x2, y2, width - x2, height - y2);
        offscr.setColor(Color.white);
        offscr.fillRect(x2, 0, width - x2, height - y2);
        offscr.fillRect(0, y2, x2, y2);
        
        // draw 'ball'
        offscr.setColor(Color.BLUE);
        offscr.fillOval((int)x, (int)y, 10, 10);
        
        // set text anti-aliasing
        if (offscr instanceof Graphics2D) {
            Graphics2D g2 = (Graphics2D)offscr;
            g2.setRenderingHint(
                RenderingHints.KEY_TEXT_ANTIALIASING,
                RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        }
        offscr.setFont(new Font("Dialog", Font.PLAIN, 24));
        offscr.setColor(Color.MAGENTA);
        offscr.drawString("Hello world!", 50, 50);
        
        // 'move' oval (ball)
        x += dx;
        y += dy;
        
        g.drawImage(offscreenImage, 0, 0, null);
    }
}