了解缓冲策略

Question

我是Java的新手。我想做一个游戏。经过大量研究，我不了解缓冲策略的工作原理。.我了解基础知识..它创建了一个屏幕外图像，您以后可以将其放入Windows对象中。

public class Marco extends JFrame {
    private static final long serialVersionUID = 1L;
    BufferStrategy bs; //create an strategy for multi-buffering.

    public Marco() {
       basicFunctions(); //just the clasics setSize,setVisible,etc
       createBufferStrategy(2);//jframe extends windows so i can call this method 
       bs = this.getBufferStrategy();//returns the buffer strategy used by this component
    }

   @Override
   public void paint(Graphics g){
      g.drawString("My game",20,40);//some string that I don't know why it does not show
      //guess is 'couse g2 overwrittes all the frame..
      Graphics2D g2=null;//create a child object of Graphics
      try{
         g2 = (Graphics2D) bs.getDrawGraphics();//this new object g2,will get the
         //buffer of this jframe?
         drawWhatEver(g2);//whatever I draw in this method will show in jframe,
         //but why??
      }finally{
         g2.dispose();//clean memory,but how? it cleans the buffer after
         //being copied to the jframe?? when did I copy to the jframe??
      }
      bs.show();//I never put anything on bs, so, why do I need to show its content??
      //I think it's a reference to g2, but when did I do this reference??
   }

   private void drawWhatEver(Graphics2D g2){
       g2.fillRect(20, 50, 20, 20);//now.. this I can show..
   }
  }

我不知道..我已经研究了很长时间了..根本没有运气..我不知道..也许所有的东西都在里面，而且它很清楚很简单，我我太愚蠢而看不见..

感谢所有的帮助.. :)

Answer 1

运作方式如下：

1. 该JFrame构造了一个BufferStrategy当你调用createBufferStrategy(2);。该BufferStrategy知道它属于那个特定实例JFrame。您正在检索它并将其存储在bs现场。
2. 到了该画画的时候，您正在Graphics2D从中检索一个bs。该Graphics2D对象绑定到拥有的内部缓冲区之一bs。绘制时，所有内容都将进入该缓冲区。
3. 当您最终调用时bs.show()，bs将使您刚才绘制的缓冲区成为的当前缓冲区JFrame。它知道如何执行此操作，因为（请参阅第1点）它知道该JFrame服务的目的。

这就是所有的事情。

通过注释代码…您应该稍微更改绘图例程。代替这个：

try{
    g2 = (Graphics2D) bs.getDrawGraphics();
    drawWhatEver(g2);
} finally {
       g2.dispose();
}
bs.show();

您应该有一个像这样的循环：

do {
    try{
        g2 = (Graphics2D) bs.getDrawGraphics();
        drawWhatEver(g2);
    } finally {
           g2.dispose();
    }
    bs.show();
} while (bs.contentsLost());

这将防止丢失丢失的缓冲帧，根据文档，这种情况可能偶尔发生。