当我从URL获取图像时，我找不到在下载时显示加载图标的方法。这是我的方法：
private void fetchAdImage(String clickedLink) {
try {
// This gets completely ignored /
adDisplayLabel.setIcon(new ImageIcon(MainFrame.class.getResource("/icons/spinner.png")));
// /
URL link = new URL(clickedLink);
ImageIcon adImage = new ImageIcon(link, "");
int difference;
if (adImage.getIconHeight() > adDisplayLabel.getHeight()) {
difference = adImage.getIconHeight() + adDisplayLabel.getHeight();
} else {
difference = adImage.getIconHeight() - adDisplayLabel.getHeight();
}
adDisplayLabel.setIcon(drawBorder(Tools.getResizedIcon(adImage, adImage.getIconWidth() - difference, adDisplayLabel.getHeight())));
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
这个想法是在"onPreUpdate"阶段将JLabel的图标更改为"微调器"图像，并在"onSuccess"阶段更改为下载的图像。问题是：这种下载方法没有这样的事情，前面的语句被完全忽略了。有没有异步方式在 Java 中下载图像？
由于@Slaw的建议(将代码包装在 Swingworker 中，一个我不知道的类(，我设法解决了这个问题。代码如下：
private void fetchAdImage(String clickedLink) {
try {
SwingWorker<ImageIcon, Void> worker = new SwingWorker<ImageIcon, Void>() {
ImageIcon adImage;
int difference;
@Override
protected ImageIcon doInBackground() throws Exception {
adDisplayLabel.setIcon(new ImageIcon(MainFrame.class.getResource("/icons/spinner.png")));
URL link = new URL(clickedLink);
adImage = new ImageIcon(link, "");
if (adImage.getIconHeight() > adDisplayLabel.getHeight()) {
difference = adImage.getIconHeight() + adDisplayLabel.getHeight();
} else {
difference = adImage.getIconHeight() - adDisplayLabel.getHeight();
}
return adImage;
}
protected void done() {
adDisplayLabel.setIcon(drawBorder(Tools.getResizedIcon(adImage, adImage.getIconWidth() - difference, adDisplayLabel.getHeight())));
}
};
worker.execute();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}