doublebuffer.java

用两个缓冲区实现鼠标事件的跟踪

/**
 * @(#)DoubleBuffer.java
 *
 * Sample Applet application
 *
 * @author 
 * @version 1.00 04/11/18
 */
 
import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class DoubleBuffer extends Applet {
	Image oimg = null;
	Graphics og = null;
		
	public void init() {
		
		Dimension d = this.getSize();
		oimg = this.createImage(d.width, d.height);
		og = oimg.getGraphics();
		
		
		this.addMouseListener(new MouseAdapter(){
			int orgX;
			int orgY;
			
			public void mousePressed(MouseEvent e){
				orgX = e.getX();
				orgY = e.getY();
			}		
			
			public void mouseReleased(MouseEvent e){
				Graphics g = getGraphics();
				g.setColor(Color.RED);
				g.drawString(orgX + ", " + orgY, orgX, orgY);
				g.drawString(e.getX() + ", " + e.getY(), e.getX(), e.getY());
				g.drawLine(orgX, orgY, e.getX(), e.getY());
				og.setColor(Color.RED);
				og.drawString(orgX + ", " + orgY, orgX, orgY);
				og.drawString(e.getX() + ", " + e.getY(), e.getX(), e.getY());
				og.drawLine(orgX, orgY, e.getX(), e.getY());				
			}
		});
	}

	public void paint(Graphics g) {
		if (oimg != null){
			g.drawImage(oimg, 0, 0, this);
		}
	}
}