从SwingWorker显示消息（Joptionpane）thread-doInBackground（）

Question

我正在运行一个长按任务按钮。我想显示任务已经开始的消息。使用swingworker，JOptionPane创建消息框，但其内容保留为空，直到任务完成。我想我的EDT正在被阻塞，因此除非任务完成，否则GUI不会更新。有什么办法来证明这个（swingutils.invokelater，因为我需要在任务开始时显示无法使用） 示例代码： -

public class myClass { 
private JFrame frame; 
private display1 dis; 

class display1 extends SwingWorker<Void,Void> 
{ 
    public Void doInBackground() throws InterruptedException 
    { 
    JOptionPane.showMessageDialog(null, 
       "Task Started"); 
     return null; 
    } 
} 
public static void main(String[] args) { 
    EventQueue.invokeLater(new Runnable() { 
     public void run() { 
      try { 
       myClass window = new myClass(); 
       window.frame.setVisible(true); 

      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
     } 
    }); 
} 


public myClass() { 
    initialize(); 
} 


private void initialize() { 
    frame = new JFrame(); 
    frame.setBounds(100, 100, 450, 300); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    frame.getContentPane().setLayout(null); 

    JButton btnNewButton = new JButton("New button"); 
    btnNewButton.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent arg0) { 
      dis=new display1(); 
      dis.execute(); 

     System.out.println("starting"); 
      for(int i=0;i<10000;i++) 
       System.out.println("this is " +i);// Long task 


     System.out.println("Finished"); 
     } 
    }); 
    btnNewButton.setBounds(166, 228, 89, 23); 
    frame.getContentPane().add(btnNewButton); 

} 
} 

Answer 1

因为SwingWorker通知事件调度线程上的任何PropertyChangeListener，只需听取绑定属性state。可能的values包括DONE,PENDING和STARTED。此TaskListener是写入控制台的示例，但在您的实现propertyChange()中更新标签是完全安全的。模式对话框是允许的但是多余的。

Answer 2

在invokeLater(Runnable);中运行的任何东西都发送到Event Dispatch Thread“gui-thread”。您的方法initialize()可以在EDT运行，但是您需要记住在EDT中正在处理与UI相关的任何操作。所以如果用户点击按钮，ActionListener代码在EDT中执行。在处理另一个UI事件时在EDT块中执行的任何长时间运行的任务。因此，您需要将您的“长期任务”移至独立线程e。 G。到SwingWorker。

如果您需要在运行任务之前显示的东西，只是把它调用swingWorker.execute();（确保，因为代码是在美国东部时间执行）之前：

button.addActionListener(new ActionListener() { 
    @Override public void actionPerformed(ActionEvent arg0) { 
     // we are are in EDT = dialog will be displayed without any problems 
     JOptionPane.showMessageDialog(null, "About to start"); 
     // executes SwingWorker's doInBackground task 
     new BackgroundTask().execute(); 
    } 
}); 

下面的代码演示了如何使用SwingWorker工作：

class BackgroundTask extends SwingWorker< 
     String/*background task's result type*/, 
     Integer/*inter-step's result type*/ 
     > 
{ 
    /** 
    * This method is designed to perform long running task in background 
    * i. e. in "non-EDT" thread = in SwingWorker thread. 
    * 
    * After method is completed, {@link #done()} is called, which is 
    * executed in "EDT" (gui-thread). 
    * 
    * Note, you can {@link #publish(Integer)} progress to {@link #process(List<V> chunks)} 
    * which is executed in "EDT" (gui-thread). 
    * 
    * You can also use {@link SwingUtilities#invokeLater(Runnable)} 
    * to send "message" to "EDT" which contains code to be executed 
    * This is similar to {@link #publish(Object)} except not-processed-yet 
    * messages are not collected and processed all at once like in 
    * {@link #publish(Object)} case. 
    */ 
    @Override 
    protected String doInBackground() throws Exception { 
     // or you can put JOptionPane.showMessageDialog(null, "About to start"); 
     // in ActionListener before calling swingWorker.execute(); 
     SwingUtilities.invokeLater(() -> JOptionPane.showMessageDialog(null, "About to start")); 
     // System.out.println("starting"); 
     for(int i = 0; i < 10000; i++) { 
      // System.out.println(i); 
      publish(i); 
     } 
     // result of the background task 
     return "Task completed"; 
    } 

    /** 
    * Method is executed in "EDT" after calling {@link #publish(Integer)}. 
    * 
    * This is the right place to update GUI about inter-step result. 
    * 
    * Note, this method is not executed immediately after calling {@link #publish(Integer)}, 
    * since EDT can process at this time sime other GUI tasks. 
    * Therefore, list contains all inter-step results send from SwingWorker 
    * to EDT which were not processed yet. 
    */ 
    @Override 
    protected void process(List<Integer> chunks) { 
     for (int number : chunks) { 
      textArea.append(number + "\n"); 
     } 
    } 

    /** 
    * Method is executed in "EDT" after {@link #doInBackground()} is finished. 
    * This is the right place to update GUI about final result. 
    */ 
    @Override 
    protected void done() { 
     String result = get(); // returns result of the doInBackground(); 
     JOptionPane.showMessageDialog(null, result); 
    } 
}