java - 在 BufferStrategy 上绘制后尝试显示帧时出错

Question

我正在尝试用java制作一个简单的游戏引擎，我目前正在渲染和显示东西，我制作了一个显示函数来显示相机在JFrame中渲染的帧

 if (cam != null)
      frame = cam.render();
    setVisible(true);
    ImageCapabilities imgBackBufCap = new ImageCapabilities(true);
    ImageCapabilities imgFrontBufCap = new ImageCapabilities(true);
    BufferCapabilities bufCap =
      new BufferCapabilities(imgFrontBufCap, imgBackBufCap, BufferCapabilities.FlipContents.COPIED);
    try {

      createBufferStrategy(2, bufCap);
    } catch (AWTException ex) {
      createBufferStrategy(2);
    }

    BufferStrategy bs = getBufferStrategy();
    Graphics g = bs.getDrawGraphics();
    if (frame != null)
      g.drawImage(frame, 0, 0, null);
    g.dispose();
    bs.show();

但是有一次它画了一个框架，我得到了这个例外，我在互联网上找不到任何有用的东西，所以我在这里问了一个问题

Exception in thread "Display" java.lang.NullPointerException: Cannot invoke "java.awt.image.VolatileImage.getGraphics()" because "this.backBuffers[i]" is null
        at java.desktop/java.awt.Component$BltBufferStrategy.showSubRegion(Component.java:4508)
        at java.desktop/java.awt.Component$BltBufferStrategy.show(Component.java:4469)
        at com.physicsEngine.rendering.Displayer.display(Displayer.java:41)
        at com.physicsEngine.Game.display(Game.java:74)
        at com.physicsEngine.Game.run(Game.java:65)
        at com.physicsEngine.Game.run(Game.java:69)
        at com.physicsEngine.Game.run(Game.java:69)
        at com.physicsEngine.Game.run(Game.java:69)
        at com.physicsEngine.Game.run(Game.java:69)
        at com.physicsEngine.Game.run(Game.java:69)
        at com.physicsEngine.Game.run(Game.java:69)

标签： javaswingjframeawtgame-engine