java - 了解 BufferStrategy

Question

我是 java 的新手。我想做一个游戏。经过大量研究，我无法理解 bufferstrategy 是如何工作的。我知道基础知识..它创建了一个屏幕外图像，您可以稍后将其放入您的 Windows 对象中..我明白了

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..而且一点运气都没有..我不知道..也许它就在那里，而且非常简单明了，我太笨了，看不出来..

感谢所有帮助..:)

Answer 1

这是它的工作原理:

1. 当您调用 createBufferStrategy(2); 时，JFrame 构造一个 BufferStrategy。 BufferStrategy 知道它属于 JFrame 的特定实例。您正在检索它并将其存储在 bs 字段中。
2. 当需要绘制您的东西时，您正在从 bs 中检索一个 Graphics2D。此 Graphics2D 对象绑定(bind)到 bs 拥有的内部缓冲区之一。在您绘制时，所有内容都会进入该缓冲区。
3. 当您最终调用 bs.show() 时，bs 将使您刚刚绘制的缓冲区成为 JFrame 的当前缓冲区>。它知道如何执行此操作，因为(参见第 1 点)它知道它服务于什么 JFrame。

这就是所有发生的事情。

通过评论您的代码...您应该稍微更改一下您的绘图例程。而不是这个:

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

你应该有这样一个循环:

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

这将防止丢失缓冲区帧，根据 the docs , 偶尔会发生。