空指針異常

Question

這是我使用上繪製一個J3D Canvas3D的圖像的代碼：

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

然而

每當我運行代碼我在g線得到一個NullPointerException .drawImage（）。我不知道是什麼導致例外，幫助將不勝感激。

Answer 1

你的ImageIcon爲空 請使用此加載您的ImageIcon正確

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

嘗試是這樣的：

圖形G = Canvas.getGraphics（）;

如果（克== NULL）{

的System.out.println（ 「未收到任何圖形從方法的getGraphics對象。」）;

}

ImageIcon的圖標=新的ImageIcon（ 「回/ loadingscreen.png」）;

如果（圖標== NULL）{

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

}