adapterspot.java

北大Java 语言程序设计 ppt课件及源码

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

public class AdapterSpot extends Applet /* no implements clause */ {
    private java.awt.Point clickPoint = null;
    private static final int RADIUS = 7;

    public void init() {
	addMouseListener(new MyMouseAdapter());
    }
    public void paint(Graphics g) {
	g.drawRect(0, 0, getSize().width - 1,
			 getSize().height - 1);
	if (clickPoint != null)
	    g.fillOval(clickPoint.x-RADIUS,
		       clickPoint.y-RADIUS,
		       RADIUS*2, RADIUS*2);
    }
    class MyMouseAdapter extends MouseAdapter {
	public void mousePressed(MouseEvent event) {
	    clickPoint = event.getPoint();
	    repaint();
	}
    }
    /* no empty methods! */
}