// 程序：處理鼠標事件
// 范例文件：HandleMouseEvent.java

import java.awt.*;
import java.applet.*;
import java.awt.event.*;   //為了處理事件

//除了Runnable之外，還實現了MouseListener及MouseMotionListener
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);            //注冊事件處理方法
      addMouseMotionListener(this);   

      setBackground(Color.gray);         //設定背景顏色
    
      AppletWidth  = getSize().width;    //取得Applet的高度
      AppletHeight = getSize().height;   //取得Applet的寬度
      clickCount   = 0;                  //mouseClick事件發(fā)生的次數
      
      //取得鐵錘圖像
      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("圖像加載中(Loading Images)...");
         MT.waitForAll();
      }
      catch(InterruptedException E){ }   //沒有進行異常處理
      
      hammerWidth   = hammer1.getWidth(this);   //取得鐵錘圖像寬度
      hammerHeight  = hammer1.getHeight(this);  //取得鐵錘圖像高度
      currentHammer = hammer1;                  //使用鐵錘圖像1
      showHammer    = false;                    //先不顯示鐵錘

      //建立次畫面
      OffScreen     = createImage(AppletWidth,AppletHeight);
      drawOffScreen = OffScreen.getGraphics();
   }

   public void start()                   //start()方法  
   {
      newThread = new Thread(this);      //建立與啟動新線程
      newThread.start();
   }

   public void stop()                    //stop()方法
   {
      newThread = null;                  //將線程設為null
   }

   public void paint(Graphics g)
   {
      //清除次畫面
      drawOffScreen.clearRect(0,0,AppletWidth,AppletHeight);

      //繪制鐵錘圖像
      if(showHammer)
         drawOffScreen.drawImage(currentHammer,hammerX,hammerY,this);

      //將次畫面貼到主畫面中
      g.drawImage(OffScreen,0,0,this);
   }

   public void update(Graphics g)        //update()方法
   {
      paint(g);                          //只單純調用paint()方法
   }
   
   public void run()
   {  
      while(newThread != null)           //動畫循環(huán)
      {  
         repaint();                      //重新繪制圖像

         try
         {
            Thread.sleep(80);            //暫停程序執(zhí)行80毫秒
         }
         catch(InterruptedException E){ }//沒有進行異常處理
      }
   }

   //=====實現MouseListener界面========================================
   public void mouseExited(MouseEvent e)      //鼠標離開Component
   {
      if(showHammer) showHammer = false;      //不繪制鐵錘
   }

   public void mouseClicked(MouseEvent e)     //鼠標按鍵被按下后放開
   {
      showStatus("揮動鐵錘" + (++clickCount) + "次");
   }

   public void mouseEntered(MouseEvent e)     //鼠標進入Component
   {
      if(!showHammer) showHammer = true;      //繪制鐵錘
   }

   public void mousePressed(MouseEvent e)     //鼠標按鍵被按下
   {
      currentHammer = hammer2;                //繪制鐵錘圖像2
   }

   public void mouseReleased(MouseEvent e)    //鼠標按鍵放開
   {
      currentHammer = hammer1;                //繪制鐵錘圖像1
   }

   //=====實現MouseMotionListener界面==================================
   public void mouseMoved(MouseEvent e)       //鼠標移動時
   {
      //設定鐵錘圖像的坐標
      hammerX = e.getX() - (hammerWidth / 2);
      hammerY = e.getY() - (hammerHeight / 2);

      //碰到邊界時的狀態(tài)
      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)     //鼠標拖曳時 
   {
      //設定鐵錘圖像的坐標
      hammerX = e.getX() - (hammerWidth / 2);
      hammerY = e.getY() - (hammerHeight / 2);

      //碰到邊界時的狀態(tài)
      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 + ")");
   }
}