trymouseadapter.java

Java 入门书的源码

//Copyright (c) 1998, Arthur Gittleman
//This example is provided WITHOUT ANY WARRANTY either expressed or implied.

/*  Revises TryMouseMotion.java using
 *  an inner class to extend MouseAdapter,
 *  overriding the mousePressed method.
 */

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

public class TryMouseAdapter extends Applet
         implements MouseMotionListener {
  private int [] x = {50,100,150};
  private int [] y = {100,50,100};
  private Polygon p = new Polygon(x,y,3);
  private int oldx;
  private int oldy;

  public void init() {
    addMouseListener(new MousePressListener());
    addMouseMotionListener(this);
  }
  public void paint(Graphics g) {
   g.fillPolygon(p);
  }
  public void mouseMoved(MouseEvent event) { }
  public void mouseDragged(MouseEvent event) {
    int x = event.getX();
    int y = event.getY(); 
    if (p.contains(x,y)){
      p.translate(x-oldx,y-oldy);
      oldx=x;
      oldy=y; 
      repaint();
    }
  } 

  class MousePressListener extends MouseAdapter {
    public void mousePressed(MouseEvent event) {
      int x = event.getX();
      int y = event.getY(); 
      if (p.contains(x,y)){
        oldx = x;
        oldy = y;
      } 
    }
  }
}