handlemouseevent.java

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// 程序：处理鼠标事件
// 范例文件：HandleMouseEvent.java

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


public class HandleMouseEvent extends Applet 
             implements Runnable,MouseListener,MouseMotionListener
{
   int          AppletWidth,AppletHeight,hammerX,hammerY,
                hammerWidth,hammerHeight,clickCount;
   Image        hammer1,hammer2,OffScreen,currentHammer;
   Thread       newThread;
   boolean      showHammer;
   Graphics     drawOffScreen;
   MediaTracker MT;

   public void init()
   {  
      addMouseListener(this);        
      addMouseMotionListener(this);   

      setBackground(Color.gray);     
    
      AppletWidth  = getSize().width;  
      AppletHeight = getSize().height; 
      clickCount   = 0;          
      
      hammer1      = getImage(getDocumentBase(),"Images/hammer1.gif");
      hammer2      = getImage(getDocumentBase(),"Images/hammer2.gif");

      MT           = new MediaTracker(this); 
      MT.addImage(hammer1,0);
      MT.addImage(hammer2,0);
      
      try
      {
         showStatus("图像载入中(Loading Images)...");
         MT.waitForAll();
      }
      catch(InterruptedException E){ }  
      
      hammerWidth   = hammer1.getWidth(this);  
      hammerHeight  = hammer1.getHeight(this); 
      currentHammer = hammer1;              
      showHammer    = false;           

      OffScreen     = createImage(AppletWidth,AppletHeight);
      drawOffScreen = OffScreen.getGraphics();
   }

   public void start()       
   {
      newThread = new Thread(this);  
      newThread.start();
   }

   public void stop()     
   {
      newThread = null;   
   }

   public void paint(Graphics g)
   {

      drawOffScreen.clearRect(0,0,AppletWidth,AppletHeight);


      if(showHammer)
         drawOffScreen.drawImage(currentHammer,hammerX,hammerY,this);


      g.drawImage(OffScreen,0,0,this);
   }

   public void update(Graphics g)    
   {
      paint(g);             
   }
   
   public void run()
   {  
      while(newThread != null)  
      {  
         repaint();            

         try
         {
            Thread.sleep(80);  
         }
         catch(InterruptedException E){ }
      }
   }


   public void mouseExited(MouseEvent e) 
   {
      if(showHammer) showHammer = false; 
   }

   public void mouseClicked(MouseEvent e) 
   {
      showStatus("挥动铁  " + (++clickCount) + "次");
   }

   public void mouseEntered(MouseEvent e) 
   {
      if(!showHammer) showHammer = true;  
   }

   public void mousePressed(MouseEvent e) 
   {
      currentHammer = hammer2;           
   }

   public void mouseReleased(MouseEvent e) 
   {
      currentHammer = hammer1;          
   }

  
   public void mouseMoved(MouseEvent e)     
   {
  
      hammerX = e.getX() - (hammerWidth / 2);
      hammerY = e.getY() - (hammerHeight / 2);

      if(hammerX <= 0) 
         hammerX = 0;
      if(hammerX >= (AppletWidth - hammerWidth))
         hammerX = AppletWidth - hammerWidth;
      if(hammerY <= 0)
         hammerY = 0;
      if(hammerY >= (AppletHeight - hammerHeight))
         hammerY = AppletHeight - hammerHeight;

      showStatus("(" + hammerX + "," + hammerY + ")");
   }  
 
   public void mouseDragged(MouseEvent e) 
   {
 
      hammerX = e.getX() - (hammerWidth / 2);
      hammerY = e.getY() - (hammerHeight / 2);

 
      if(hammerX <= 0) 
         hammerX = 0;
      if(hammerX >= (AppletWidth - hammerWidth))
         hammerX = AppletWidth - hammerWidth;
      if(hammerY <= 0)
         hammerY = 0;
      if(hammerY >= (AppletHeight - hammerHeight))
         hammerY = AppletHeight - hammerHeight;

      showStatus("(" + hammerX + "," + hammerY + ")");
   }
}