Java 如何在线程和小程序中使用双缓冲

我有一个关于何时调用绘制和更新方法的问题？？ 我有一个游戏小程序，我想使用双缓冲。但我不能使用它。问题是 在我的游戏中，有一个球在run（）方法中移动。我想知道如何使用双缓冲来交换屏幕外图像和当前图像。有人请帮忙

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当同时存在update（）和paint（）方法时，首先调用哪一个，何时以及为什么

您可以使用的一种方法是向小程序添加画布，然后为该画布创建缓冲策略。抽象代码，您可能会得到硬件加速

代码如下：--扩展AppletGameCore并定义实现所需方法的您自己的子类

import java.awt.Canvas;
import java.awt.Graphics2D;
import java.awt.Dimension;
import java.awt.image.BufferStrategy;
import java.applet.Applet;

/**
*AppletGameCore.java
*@author David Graham
*/

public abstract class AppletGameCore extends Applet implements Runnable
{
     private BufferStrategy bufferStrategy;
     private Canvas drawArea;/*Drawing Canvas*/
     private boolean stopped = false;/*True if the applet has been destroyed*/
     private int x = 0;

     public void init()
     {
           Thread t = new Thread(this);
           drawArea = new Canvas();
           setIgnoreRepaint(true);
           t.start();
     }

     public void destroy()
     {
           stopped = true;

           /*Allow Applet to destroy any resources used by this applet*/
           super.destroy();
     }

     public void update()
     {
           if(!bufferStrategy.contentsLost())
           {
                 //Show bufferStrategy
                 bufferStrategy.show();
           }
     }

     //Return drawArea's BufferStrategy
     public BufferStrategy getBufferStrategy()
     {
           return bufferStrategy;
     }

     //Create drawArea's BufferStrategies
     public void createBufferStrategy(int numBuffers)
     {
           drawArea.createBufferStrategy(numBuffers);
     }

     //Subclasses should override this method to do any drawing
     public abstract void draw(Graphics2D g);

     public void update(Graphics2D g)
     {
           g.setColor(g.getBackground());
           g.fillRect(0,0,getWidth(),getHeight());
     }

     //Update any sprites, images, or primitives
     public abstract void update(long time);

     public Graphics2D getGraphics()
     {
           return (Graphics2D)bufferStrategy.getDrawGraphics();
     }

     //Do not override this method      
     public void run()
     {
           drawArea.setSize(new Dimension(getWidth(),getHeight()));
           add(drawArea);
           createBufferStrategy(2);
           bufferStrategy = drawArea.getBufferStrategy();

           long startTime = System.currentTimeMillis();
           long currTime = startTime;

           //animation loop
           while(!stopped)
           {
                 //Get time past
                 long elapsedTime = System.currentTimeMillis()-currTime;
                 currTime += elapsedTime;

                 //Flip or show the back buffer
                 update();

                 //Update any sprites or other graphical objects
                 update(elapsedTime);

                 //Handle Drawing
                 Graphics2D g = getGraphics();
                 update(g);
                 draw(g);

                 //Dispose of graphics context
                 g.dispose();
           }

     }
}