通过不同的线程访问变量和摆动组件 [英] accessing variables and swing components through different threads

问题描述

这个问题与我提出的问题有点相关此处。
现在，我有一个Controller类，它由main方法和所有swing组件组成。有一个名为VTOL的类，它由一个名为altitude的变量组成（我现在已声明此变量为volatile）。

This question is related somewhat to the one i asked HERE. Now, i have a class "Controller" which consists of the main method and all the swing components. there is a class named "VTOL" which consists of a variable named "altitude"(i have declared this variable volatile as of now).

这是一个包含的类在后台运行的线程：

here is a class that consists of a thread which runs in the background:

import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author Vineet
 */
public class Gravity extends Thread {

    String altStr;
    double alt;
    Controller ctrl = new Controller();

    @Override
    public void run() {
        while (true) {
            alt=VTOL.altitude;
            System.out.println(alt);
            alt = alt-0.01;
            VTOL.altitude= (int) alt;
            altStr=new Integer(VTOL.altitude).toString();
            ctrl.lblAltitude.setText(altStr);
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

    }
}

首先，我最初面临的问题是我无法更新高度的值，它在整个程序执行期间保持为0。所以我宣称它是不稳定的（我不知道它是不是一个好习惯）

Firstly, the problem i was facing initially was that i couldnt update value of "altitude" it remained 0 throughout the execution of program. So i declared it as volatile (I dont know if its a good practice)

其次，在Controller类中有一个名为lblAltitude的jLabel，我想更新它的在这个帖子中改变了它的值，但不知怎的，这没有发生。
我该怎么做？

Secondly, there is a jLabel in Controller class named "lblAltitude", i wish to update its value as its changed in this thread, but somehow thats not happening. How can i do that?

推荐答案

解决方法是使用SwingPropertyChangeSupport对象，使海拔高度达到绑定 具有此支持对象的属性，让您的GUI监听器通知此模型类，从而通知GUI高度变化。

A solution is to use a SwingPropertyChangeSupport object, to make altitude a "bound" property with this support object, to have your GUI listener to this model class and to thereby notify the GUI of changes in altitude.

例如，

import java.beans.PropertyChangeListener;
import javax.swing.event.SwingPropertyChangeSupport;

public class Gravity implements Runnable {
   public static final String ALTITUDE = "altitude";
   private SwingPropertyChangeSupport swingPcSupport = new SwingPropertyChangeSupport(this);
   private volatile double altitude;

   @Override
   public void run() {
      while (true) {
         double temp = altitude + 10;
         setAltitude(temp); // fires the listeners
         try {
            Thread.sleep(10);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }

   }

   public double getAltitude() {
      return altitude;
   }

   public void setAltitude(double altitude) {
      Double oldValue = this.altitude;
      Double newValue = altitude;

      this.altitude = newValue;

      // this will be fired on the EDT since it is a SwingPropertyChangeSupport object
      swingPcSupport.firePropertyChange(ALTITUDE, oldValue, newValue);
   }

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

   public void removePropertyChangeListener(PropertyChangeListener listener) {
      swingPcSupport.removePropertyChangeListener(listener);
   }


}

了解更多完整的可运行示例：

For a more complete runnable example:

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
import javax.swing.event.SwingPropertyChangeSupport;

public class GravityTestGui extends JPanel {
   private static final long ALT_SLEEP_TIME = 400;
   private static final double ALT_DELTA = 5;
   JLabel altitudeLabel = new JLabel("     ");
   private Gravity gravity = new Gravity(ALT_SLEEP_TIME, ALT_DELTA);

   public GravityTestGui() {
      add(new JLabel("Altitude:"));
      add(altitudeLabel);

      gravity.addPropertyChangeListener(new PropertyChangeListener() {

         @Override
         public void propertyChange(PropertyChangeEvent pcEvt) {
            if (Gravity.ALTITUDE.equals(pcEvt.getPropertyName())) {
               String altText = String.valueOf(gravity.getAltitude());
               altitudeLabel.setText(altText);
            }
         }
      });

      new Thread(gravity).start();
   }

   private static void createAndShowGui() {
      GravityTestGui mainPanel = new GravityTestGui();

      JFrame frame = new JFrame("GravityTest");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }


}

class Gravity implements Runnable {
   public static final String ALTITUDE = "altitude";
   private SwingPropertyChangeSupport swingPcSupport = new SwingPropertyChangeSupport(this);
   private volatile double altitude;
   private long sleepTime;
   private double delta;

   public Gravity(long sleepTime, double delta) {
      this.sleepTime = sleepTime;
      this.delta = delta;
   }

   @Override
   public void run() {
      while (true) {
         double temp = altitude + delta;
         setAltitude(temp); // fires the listeners
         try {
            Thread.sleep(sleepTime);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }

   }

   public double getAltitude() {
      return altitude;
   }

   public void setAltitude(double altitude) {
      Double oldValue = this.altitude;
      Double newValue = altitude;

      this.altitude = newValue;

      // this will be fired on the EDT since it is a SwingPropertyChangeSupport object
      swingPcSupport.firePropertyChange(ALTITUDE, oldValue, newValue);
   }

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

   public void removePropertyChangeListener(PropertyChangeListener listener) {
      swingPcSupport.removePropertyChangeListener(listener);
   }
}

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