制作一个显示“请等待”的摇摆线程的JDialog [英] Make a swing thread that show a "Please Wait" JDialog

问题描述

问题是这样的：

我正在运行一个swing应用程序，在某个时刻对话框需要输入用户名和密码并按下ok。

我希望当用户按下ok时，swing应用程序按此顺序执行：

The problem is this:
I've a swing application running, at a certain point a dialog requires to insert username and password and to press "ok".
I would like that when the user press "ok" the swing application does in this order:

1. 打开a请等待JDialog
   


2. 进行一些操作（最终显示其他一些JDialog或JOptionPane）
   


3. 当它完成操作关闭请等待JDialog
   

这是我在okButtonActionPerformed（）中编写的代码：

This is the code that I wrote in the okButtonActionPerformed():

private void okButtonActionPerformed(java.awt.event.ActionEvent evt) { 
    //This class simply extends a JDialog and contains an image and a jlabel (Please wait)
    final WaitDialog waitDialog = new WaitDialog(new javax.swing.JFrame(), false);    
    waitDialog.setVisible(true);
    ... //Do some operation (eventually show other JDialogs or JOptionPanes)
    waitDialog.dispose()
}

这段代码显然不起作用，因为当我在同一个线程中调用waitDialog时它会阻塞所有代码直到我不关闭它。

所以我尝试在不同的线程中运行它：

This code obviously doesn't works because when I call the waitDialog in the same thread it blocks all till I don't close it.
So I tried to run it in a different thread:

private void okButtonActionPerformed(java.awt.event.ActionEvent evt) { 
    //This class simply extends a JDialog and contains an image and a jlabel (Please wait)
    final WaitDialog waitDialog = new WaitDialog(new javax.swing.JFrame(), false);    
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            waitDialog.setVisible(true);
        }
    });
    ... //Do some operation (eventually show other JDialogs or JOptionPanes)
    waitDialog.dispose()
}

但这也不起作用，因为waitDialog不会立即显示，但只有在操作完成后才会显示他们的工作（当他们显示joption窗格时你已登录为。 ..）

But also this doesn't work because the waitDialog is not displayed immediately but only after that the operation completed their work (when they show a joption pane "You are logged in as...")

我还尝试使用invokeAndWait而不是invokeLater，但在这种情况下它会引发异常：

I also tried to use invokeAndWait instead of invokeLater but in this case it throws an exception:

Exception in thread "AWT-EventQueue-0" java.lang.Error: Cannot call invokeAndWait from the event dispatcher thread

我该怎么办？

推荐答案

考虑使用SwingWorker进行后台工作，然后在SwingWorker的 done（）方法中关闭对话框，或者在添加到的PropertyChangeListener中关闭对话框（我的偏好） SwingWorker。

Consider using a SwingWorker to do your background work, and then closing the dialog either in the SwingWorker's done() method or (my preference) in a PropertyChangeListener that is added to the SwingWorker.

例如，

import java.awt.BorderLayout;
import java.awt.Dialog.ModalityType;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;    
import javax.swing.*;

public class PleaseWaitEg {
   public static void main(String[] args) {
      JButton showWaitBtn = new JButton(new ShowWaitAction("Show Wait Dialog"));
      JPanel panel = new JPanel();
      panel.add(showWaitBtn);
      JFrame frame = new JFrame("Frame");
      frame.getContentPane().add(panel);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);

   }
}

class ShowWaitAction extends AbstractAction {
   protected static final long SLEEP_TIME = 3 * 1000;

   public ShowWaitAction(String name) {
      super(name);
   }

   @Override
   public void actionPerformed(ActionEvent evt) {
      SwingWorker<Void, Void> mySwingWorker = new SwingWorker<Void, Void>(){
         @Override
         protected Void doInBackground() throws Exception {

            // mimic some long-running process here...
            Thread.sleep(SLEEP_TIME);
            return null;
         }
      };

      Window win = SwingUtilities.getWindowAncestor((AbstractButton)evt.getSource());
      final JDialog dialog = new JDialog(win, "Dialog", ModalityType.APPLICATION_MODAL);

      mySwingWorker.addPropertyChangeListener(new PropertyChangeListener() {

         @Override
         public void propertyChange(PropertyChangeEvent evt) {
            if (evt.getPropertyName().equals("state")) {
               if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
                  dialog.dispose();
               }
            }
         }
      });
      mySwingWorker.execute();

      JProgressBar progressBar = new JProgressBar();
      progressBar.setIndeterminate(true);
      JPanel panel = new JPanel(new BorderLayout());
      panel.add(progressBar, BorderLayout.CENTER);
      panel.add(new JLabel("Please wait......."), BorderLayout.PAGE_START);
      dialog.add(panel);
      dialog.pack();
      dialog.setLocationRelativeTo(win);
      dialog.setVisible(true);
   }
}

注意：

• 关键概念是设置所有内容，添加PropertyChangeListener，运行SwingWorker，所有 显示模态对话框，因为一旦显示模态对话框，来自调用代码的所有代码流都被冻结（如您所知）。


• 为什么我更喜欢PropertyChangeListener来使用done方法（正如Elias在这里得到的体面回答所示，我已经投票了） - 使用监听器提供了更多的关注点分离，松耦合。通过这种方式，SwingWorker不必知道正在使用它的GUI代码。

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