java - 图像 getWidth 和 getHeight 不恰本地返回 -1

Question

为什么会这样:

URL url = MinecraftPlatformGame.class.getResource("images/diamondPick.png");
image = Toolkit.getDefaultToolkit().getImage(url); 
int width = image.getWidth(null);
int height = image.getHeight(null);
System.out.println(width);
System.out.println(height);

宽度和高度均返回-1

编辑:在我找到答案之前，我的问题实际上是我应该如何修复它。 我通过执行以下操作修复了它:

URL url = MinecraftPlatformGame.class.getResource("images/diamondPick.png");
image = Toolkit.getDefaultToolkit().getImage(url); 
MediaTracker mTracker = new MediaTracker(this);
  mTracker.addImage(image,1);
        try {
            mTracker.waitForID(1);
        } catch (InterruptedException ex) {
            Logger.getLogger(MinecraftPlatformGame.class.getName()).log(Level.SEVERE, null, ex);
        }
int width = image.getWidth(null);
int height = image.getHeight(null);
System.out.println(width);
System.out.println(height);

url = MinecraftPlatformGame.class.getResource("images/gui.png");
image1 = Toolkit.getDefaultToolkit().getImage(url);
  mTracker.addImage(image1,2);
        try {
            mTracker.waitForID(2);
        } catch (InterruptedException ex) {
            Logger.getLogger(MinecraftPlatformGame.class.getName()).log(Level.SEVERE, null, ex);
        }
        width = image1.getWidth(null);
height = image1.getHeight(null);
System.out.println(width);
System.out.println(height);

我现在遇到的问题是，这似乎不是很有效，而且我似乎也不需要那么多代码来导入两个图像并指定大小。有没有更好、更高效、更简单的方法来做到这一点？

Answer 1

根据 Javadoc:

If the width is not yet known, this method returns -1 and the specified ImageObserver object is notified later.

为了响应您的编辑，并根据 Russell 的评论，使用 ImageIO.read() 来获取完全加载的图像。