core java当中的MouseTest小程序

声明：该程序是从core java中copy过来的，用于个人学习。
测试鼠标的响应的事件
import javax.swing.*;
import java.util.*;
import java.awt.geom.*;
import java.awt.event.*;
import java.awt.*;
public class MouseTest {
public static void main(String[]args){
    MouseFrame  frame=new MouseFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.show();
}
}
class MouseFrame extends JFrame{
    public MouseFrame(){
        setTitle("MouseTest--phenix");
        setSize(this.DEFAULT_WIDTH,this.DEFAULT_HEIGHT);
        MousePanel  panel=new MousePanel();
        Container  contentPane=getContentPane();
        contentPane.add(panel);
    }
    public static final int DEFAULT_WIDTH=300;
    public static final int DEFAULT_HEIGHT=300;
}
class MousePanel extends JPanel{
    private static final int SIDELENGTH=20;
    private ArrayList squares;
    private Rectangle2D  current;
    public MousePanel(){
        squares =new ArrayList();
        current=null;
        addMouseListener(new MouseHandler());
        addMouseMotionListener(new MouseMotionHandler());
    }
    public Rectangle2D  find(Point2D p){
        for(int i=0;i<squares.size();i++){
            Rectangle2D  r=(Rectangle2D)squares.get(i);
            if(r.contains(p))return r;
        }
        return null;
    }
    //添加一个矩形
    public void add(Point2D p){
        double  x=p.getX();
        double  y=p.getY();
        
        current=new Rectangle2D.Double(x-SIDELENGTH/2,y-SIDELENGTH/2,SIDELENGTH,SIDELENGTH);
        squares.add(current);
        repaint();
    }
    //移除矩形
    public void remove(Rectangle2D p){
        if(p==null)return;
        if(p==current)current=null;
        squares.remove(p);
        repaint();
    }
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        Graphics2D g2=(Graphics2D)g;
        for(int i=0;i<squares.size();i++){
            g2.draw((Rectangle2D)squares.get(i));
        }
    }
    private class MouseHandler extends MouseAdapter{
    public void mousePressed(MouseEvent event){
        current=find(event.getPoint());
        if(current==null){
            add(event.getPoint());
        }
    }
    public void mouseClicked(MouseEvent event){
        current=find(event.getPoint());
        if(current!=null&&event.getClickCount()>=2){
            remove(current);
        }
    }
    }
    private class MouseMotionHandler implements MouseMotionListener{
        public void mouseMoved(MouseEvent event){
            if(find(event.getPoint())==null){
                setCursor(Cursor.getDefaultCursor());
            }
            else
            {
                setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
            }
        }
        public void mouseDragged(MouseEvent event){
            if(current!=null){
                int x=event.getX();
                int y=event.getY();
                current.setFrame(x-SIDELENGTH/2,y-SIDELENGTH/2,SIDELENGTH,SIDELENGTH);
                repaint();
            }
        }
    }
}