以下是另一个'如何让JTextArea实时更新'的问题。我已经阅读了现有的所有帖子,我认为我正确地将其解读。但是,我仍然遇到同样的问题 - 我的JTextArea在环路完成之前不会更新,然后在一次大爆炸中更新。有人可以看到我做错了吗?我看不到它。谢谢!
编辑:切换文本区域更新被调用的方法。但我仍然有同样的结果!
private void saveImagesToDisk() {
textArea.append("\nPreparing to save photos to photos directory\n\n");
for (MediaFeedData mfd : imagesMetaDataList) {
try {
String imageURL = mfd.getImages().getLowResolution().getImageUrl();
final String filename = mfd.getId(); // just name the file using the image id from instagram
System.out.println(filename);
SaveImageFromUrl.saveImage(imageURL, filename, textArea);
} catch (IOException e) {
e.printStackTrace();
}
}
}
然后,在保存方法中,我有:
public class SaveImageFromUrl {
public static Boolean saveImage(final String imageUrl, String destinationFile, final JTextArea textArea) throws IOException {
String directoryName = "photos";
if (!makePhotosDirectory(directoryName, textArea)) {return false;}
File file = new File(directoryName, destinationFile);
URL url = new URL(imageUrl);
InputStream is = url.openStream();
OutputStream os = new FileOutputStream(file);
byte[] b = new byte[2048];
int length;
while ((length = is.read(b)) != -1) {
os.write(b, 0, length);
}
is.close();
os.close();
new Thread() {
public void run() {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
textArea.append(imageUrl + " written to photos directory\n");
}
});
}
}.start();
return true;
}
答案 0 :(得分:2)
for循环和下面方法中的代码都需要在后台线程中调用,这是你没有做到的。
if (SaveImageFromUrl.saveImage(imageURL, filename, textArea)) {
如果时间密集型代码不是在后台调用的代码,那么仅使用后台线程将无济于事。
考虑使用SwingWorker,比如......
private void saveImagesToDisk() {
textArea.append("\nPreparing to save photos to photos directory\n\n");
final SwingWorker<Void, String> imageWorker = new SwingWorker<Void, String>() {
@Override
protected Void doInBackground() throws Exception {
for (MediaFeedData mfd : imagesMetaDataList) {
final String imageURL = mfd.getImages().getLowResolution().getImageUrl();
final String filename = mfd.getId();
System.out.println(filename);
String textToPublish = "";
if (SaveImageFromUrl.saveImage(imageURL, filename, textArea)) {
textToPublish = filename + " written to photos directory\n";
} else {
textToPublish = filename + " not saved!\n";
}
// publish String so it can be used in the process method
publish(textToPublish);
}
return null;
}
@Override
protected void process(List<String> chunks) {
// Strings sent to the EDT by the publish method
// This called on the Swing event thread.
for (String chunk : chunks) {
textArea.append(chunk);
}
}
};
imageWorker.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
try {
// need to call this on the event thread
// to catch any exceptions that have occurred int he Swing Worker
imageWorker.get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
// TODO catch exceptions buried in this guy
e.printStackTrace();
}
}
}
});
// run our SwingWorker
imageWorker.execute();
}
有关详细信息,请阅读Concurrency in Swing。