使用覆盖更新方法的Java双缓冲区抛出堆栈溢出

Question

我想通过重写我的JPanel的更新方法来实现我的游戏在Java中的双重缓冲，我做所有常见的代码等，仍然不会工作，它抛出一个堆栈溢出错误，下面是具体的错误：

Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError 
     at java.awt.Rectangle.<init>(Rectangle.java:193) 
     at java.awt.Rectangle.<init>(Rectangle.java:208) 
     at sun.awt.image.BufImgSurfaceData.getBounds(BufImgSurfaceData.java:369) 
     at sun.java2d.loops.GraphicsPrimitive.convertFrom(GraphicsPrimitive.java:533) 
     at sun.java2d.loops.GraphicsPrimitive.convertFrom(GraphicsPrimitive.java:523) 
     at sun.java2d.loops.MaskBlit$General.MaskBlit(MaskBlit.java:171) 
     at sun.java2d.loops.Blit$GeneralMaskBlit.Blit(Blit.java:186) 
     at sun.java2d.pipe.DrawImage.blitSurfaceData(DrawImage.java:927) 
     at sun.java2d.pipe.DrawImage.renderImageCopy(DrawImage.java:550) 
     at sun.java2d.pipe.DrawImage.copyImage(DrawImage.java:54) 
     at sun.java2d.pipe.DrawImage.copyImage(DrawImage.java:982) 
     at sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:2979) 
     at sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:2964) 
     at epicgame.Menu.displayMenu(Menu.java:71) 
     at epicgame.GUI$1.paintComponent(GUI.java:64) 
     at javax.swing.JComponent.paint(JComponent.java:1029) 
     at epicgame.GUI$1.update(GUI.java:117) 
     at epicgame.GUI$1.paintComponent(GUI.java:98) 
     at javax.swing.JComponent.paint(JComponent.java:1029) 

我的代码是不是特别复杂或者：

mainPanel = new JPanel() 
     { 
      @Override protected void paintComponent(Graphics g) 
      { 
       //super.paintComponent(g); 

       if(menuEnabled == 1) 
       { 
        Menu.displayMenu(g, mainPanel); 
       } 
       else if(gameNum == 1) 
       { 
        StreetFighter.StreetFighter(g, mainPanel); 

        // Calls the controls method within the controls class. 
        Controls.controls(Calendar.getInstance().getTimeInMillis() - timeOld); 
        timeOld = Calendar.getInstance().getTimeInMillis(); 
       } 
       else if(gameNum == -1) 
       { 
        Menu.scoreBoard(g, mainPanel); 
        if(loaded != true) 
        { 
         Menu.loadScoreBoard(mainPanel); 
         loaded = true; 
        } 
       } 
       if(gameNum > 0) 
       { 
        if(longcat == true && longcatloaded != true) 
        { 
         Extras.loadLongCat(); 
         longcatloaded = true; 
        } 
        if(longcatloaded == true && longcat == true) 
        { 
         Extras.displayLongCat(g, mainPanel); 
        } 
       } 

       // Causes an infinite loop, e.g makes the screen render over and over. 
       //repaint(); 
       update(g); 
      } 

      @Override public void update(Graphics g) 
      { 
       System.err.println("Updating screen and using double buffer!"); 

       // initialize buffer 
       if(dbImage == null) 
       { 
        dbImage = createImage (this.getSize().width, this.getSize().height); 
        dbg = dbImage.getGraphics(); 
       } 
       // clear screen in background 
       dbg.setColor (getBackground()); 
       dbg.fillRect (0, 0, this.getSize().width, this.getSize().height); 
       // draw elements in background 
       dbg.setColor (getForeground()); 

       paint(dbg); 

       // draw image on the screen 
       g.drawImage (dbImage, 0, 0, this); 

       try 
       { 
        Thread.sleep(200); 

       } 
       catch (InterruptedException ex) 
       { 
        System.err.print("cant delay repaint."); 
       } 
      } 
     }; 

我希望有人能指出我哪里错了，我我想这可能与更新被调用的次数有关，或者可能的更新是错误的方法？

Answer 1

请不要拨打或update()方法从paintComponent()。

也不要在任何绘画方法中调用Thread.sleep()。相反，创建一个线程，每x毫秒更新一次游戏模型，然后在您的自定义组件上调用repaint()，以覆盖paintComponent()，以便绘制游戏状态。

Answer 2

您需要在每一帧完成后调用g.dispose()，否则它将永远不会从内存中释放，并且会出现您看到的堆栈溢出错误。 http://download.oracle.com/javase/1.3/docs/api/java/awt/Graphics.html

Answer 3

您在组件的paintComponent中调用paint，这将导致组件继续重新绘制自己。这将导致StackOverflowException。此外，API告诫一个关于应用程序中调用明确开发商paint：

Invoked by Swing to draw components. Applications should not invoke paint directly, but should instead use the repaint method to schedule the component for redrawing.

This method actually delegates the work of painting to three protected methods: paintComponent, paintBorder, and paintChildren. They're called in the order listed to ensure that children appear on top of component itself. Generally speaking, the component and its children should not paint in the insets area allocated to the border. Subclasses can just override this method, as always. A subclass that just wants to specialize the UI (look and feel) delegate's paint method should just override paintComponent.