MVC 进度条线程 [英] MVC Progress Bar Threading

问题描述

我在我的设计中使用了 MVC 模式，当用户按下搜索按钮时，我在模型中调用搜索，但我还想使用从该模型返回的信息更新进度条.

I am using an MVC pattern for my design, when a user presses the search button, I call a search in the model, but I also want to update a progress bar with information returned from that model.

我尝试使用 Swingworker，但进度条没有更新.我怀疑我的线程有问题.

I have tried using a swingworker, but the progress bar does not update. I suspect I am doing something wrong with my threading.

我在控制器中定义的按钮是:

My button as defined in the controller is:

 class SearchBtnListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            _view.displayProgress();  
        }    
}

这会在模型中调用搜索，并在视图中进行以下调用:

This calls the search in the model and has the following call in the view:

public void displayProgress() {

    TwoWorker task = new TwoWorker();
    task.addPropertyChangeListener(new PropertyChangeListener() {

         @Override
         public void propertyChange(PropertyChangeEvent e) {
             if ("progress".equals(e.getPropertyName())) {
                _progressBar.setValue((Integer) e.getNewValue());
             }
         }

     });
     task.execute();             
}      


private class TwoWorker extends SwingWorker<Void, Void> {        
    @Override
    protected Void doInBackground() throws Exception {
        _model.startSearch(getTerm());                  // time intensive code
        File file = new File("lock");           
        while (file.exists()){
            setProgress(_model.getStatus());
            System.out.println(_model.getStatus()); // never called
        }           
        return null;
    }  

    protected void done(){
        updateMain();
    }
}

在用于测试的模型中定义的虚拟函数:

Dummy function defined in Model for testing:

public int getStatus(){
    Random r = new Random();
    return r.nextInt();
}

推荐答案

不要打电话

_progressBar.setValue(_model.getStatus());

在您的 SwingWorker 中，因为这是从后台线程调用 Swing 代码，并且无论如何都是 PropertyChangeListener 的用途.相反，只需设置进度属性即可.

from within your SwingWorker as this is calling Swing code from a background thread and is what the PropertyChangeListener is for anyway. Instead, just set the progress property, that's all.

此外，不要从 doInBackground 方法中调用 done()，因为这需要由 SwingWorker 从 EDT 调用.所以让 SwingWorker 自己在实际完成时调用这个方法.

Also, don't call done() from within the doInBackground method as this needs to be called from the EDT by the SwingWorker. So let the SwingWorker itself call this method when it is in fact done.

另外，Done() 应该是 done() —— 第一个字母不应该大写，并且你应该在这段代码中使用 @Override 注释，这样你就可以确保你正确地覆盖了方法.

Also, Done() should be done() -- the first letter shouldn't be capitalized, and you should use @Override annotations in this code so you can be sure that you're overriding methods correctly.

另外，这是做什么的?

 _model.startSearch(_view.getTerm());

它是否调用了需要一段时间才能完成的代码?这应该从 SwingWorker doInBackground 本身内部初始化吗?

Does it call code that takes a while to complete? Should this be initialized from within the SwingWorker doInBackground itself?

另一种选择是给模型一个绑定的 int 属性，比如称为进度，然后向它添加一个 PropertyChangeListener 直接让它更新 JProgressBar.例如，

Another option is to give the Model a bound int property, say called progress, and then add a PropertyChangeListener to it directly letting it update the JProgressBar. For example,

import java.awt.BorderLayout;
import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

import javax.swing.*;

public class MVC_ProgressBarThread {
   private static void createAndShowUI() {
      MVC_View view = new MVC_View();
      MVC_Model model = new MVC_Model();
      MVC_Control control = new MVC_Control(view, model);
      view.setControl(control);

      JFrame frame = new JFrame("MVC_ProgressBarThread");
      frame.getContentPane().add(view);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

@SuppressWarnings("serial")
class MVC_View extends JPanel {
   private MVC_Control control;
   private JProgressBar progressBar = new JProgressBar();
   private JButton startActionButton = new JButton("Start Action");

   public MVC_View() {
      startActionButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            buttonActionPerformed();
         }
      });

      JPanel buttonPanel = new JPanel();
      buttonPanel.add(startActionButton);
      setLayout(new BorderLayout());
      add(buttonPanel, BorderLayout.NORTH);
      add(progressBar, BorderLayout.CENTER);
   }

   public void setControl(MVC_Control control) {
      this.control = control;
   }

   private void buttonActionPerformed() {
      if (control != null) {
         control.doButtonAction();
      }
   }

   public void setProgress(int progress) {
      progressBar.setValue(progress);
   }

   public void start() {
      startActionButton.setEnabled(false);
   }

   public void done() {
      startActionButton.setEnabled(true);
      setProgress(100);
   }
}

class MVC_Control {
   private MVC_View view;
   private MVC_Model model;

   public MVC_Control(final MVC_View view, final MVC_Model model) {
      this.view = view;
      this.model = model;
      model.addPropertyChangeListener(new PropertyChangeListener() {
         public void propertyChange(PropertyChangeEvent pce) {
            if (MVC_Model.PROGRESS.equals(pce.getPropertyName())) {
               view.setProgress((Integer)pce.getNewValue());
            }
         }
      });
   }

   public void doButtonAction() {
      view.start();
      SwingWorker<Void, Void> swingworker = new SwingWorker<Void, Void>() {
         @Override
         protected Void doInBackground() throws Exception {
            model.reset();
            model.startSearch();
            return null;
         }

         @Override
         protected void done() {
            view.done();
         }
      };
      swingworker.execute();
   }

}

class MVC_Model {
   public static final String PROGRESS = "progress";
   private static final int MAX = 100;
   private static final long SLEEP_DELAY = 100;
   private int progress = 0;
   private PropertyChangeSupport pcs = new PropertyChangeSupport(this);

   public void setProgress(int progress) {
      int oldProgress = this.progress;
      this.progress = progress;

      PropertyChangeEvent evt = new PropertyChangeEvent(this, PROGRESS, oldProgress, progress);
      pcs.firePropertyChange(evt);
   }

   public void reset() {
      setProgress(0);
   }

   public void addPropertyChangeListener(PropertyChangeListener listener) {
      pcs.addPropertyChangeListener(listener);
   }

   public void startSearch() {
      for (int i = 0; i < MAX; i++) {
         int newValue = (100 * i) / MAX;
         setProgress(newValue);
         try {
            Thread.sleep(SLEEP_DELAY);
         } catch (InterruptedException e) {}
      }
   }
}

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