java - Graphics.drawImage() 处的空指针异常

Question

这是我用来在 J3D Canvas3D 上绘制图像的代码：

    Graphics g = Canvas.getGraphics(); //Canvas is the Canvas3D
    g.drawImage(new ImageIcon("back/loadingscreen.png").getImage(),
            0, 0, Canvas);

但是，每当我运行代码时，我都会在 g.drawImage() 行得到 NullPointerException。我不知道是什么导致了异常，我们将不胜感激。

Answer 1

您的 ImageIcon 为空，请使用它来正确加载您的 ImageIcon

 InputStream stream = this.getClass().getClassLoader().getResourceAsStream("back/loadingscreen.png");
     BufferedImage bufferedImage=ImageIO.read(stream);
     ImageIcon icon= new ImageIcon(bufferedImage);

     Graphics g = Canvas.getGraphics(); 
        g.drawImage(icon.getImage(), 0, 0, Canvas);

Answer 2

尝试这样的事情：

图形 g = Canvas.getGraphics();

如果（g==null）{

System.out.println("没有从 getGraphics 方法接收到任何 Graphics 对象。");

}

ImageIcon icon = new ImageIcon("back/loadingscreen.png");

如果（图标==空）{

System.out.println("The icon is not received meaning the URL path (back/laodingscreen.png) is probably wrong.");

}