ProgressBar propertyychangeListener 在这种情况下不更新

Question

我在包含进度条的MainPanel 中有一个静态布尔变量inProgress。通信器类将此变量的值更改为真假。

propertyListener如下

          @Override
          public void propertyChange(PropertyChangeEvent evt) {

            System.out.println("Property change check none");
            if(true ==MainPanel.inProgress){
                progressInformationPanel.getProgressBar().setIndeterminate(true);
                progressInformationPanel.getCurrentProcesLabel().setText("Processing...");
            }
            else if(false ==MainPanel.inProgress){
                System.out.println("Property change check none" + false);
                progressInformationPanel.getProgressBar().setIndeterminate(false);
              progressInformationPanel.getCurrentProcesLabel().setText("Finished....");
            }
        }
    });

通信器类是观察者。那是在听别的课。现在，一旦有进度通信器类更新 MainPanel 的变量，但 propertyChangeListener 不动作。我不知道为什么会这样。也请在此处查看我的链接Question

这里是 SSCCE

import java.awt.GridBagLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.JFrame;
import javax.swing.JProgressBar;


public class MainFrame extends JFrame{

    public static  boolean inProgress = true;
    private JProgressBar bar;
    public Communicator diplayFacade;
    public MainFrame() {
        this.setSize(500, 500);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        diplayFacade = new Communicator();
        bar = new JProgressBar();
        setLayout(new GridBagLayout());
        add(bar);
        addProgressListener();
    }



    public void addProgressListener(){
        bar.addPropertyChangeListener(new PropertyChangeListener() {

            @Override
            public void propertyChange(PropertyChangeEvent evt) {

                if(true == MainFrame.inProgress){
                    System.out.println("Property change check none" + true);
                    bar.setIndeterminate(true);
                }
                else if(false ==MainFrame.inProgress){
                    System.out.println("Property change check none" + false);
                    bar.setIndeterminate(false);

                }


            }
        });
    }

    public static void main(String[] args) {
        MainFrame frame = new MainFrame();
        frame.diplayFacade.methodCalled();


    }

}

还有 Communicator 类

import javax.swing.JOptionPane;

public class Communicator {



    public void methodCalled(){

        JOptionPane.showInputDialog("Hi");
        MainFrame.inProgress = true;
    }
}

Answer 1

问题是，我认为您不了解 PropertyChangeListener 的实际作用。 PropertyChangeListener 监视其注册到的 Object 的属性的更改。

此通知不是偶然或自动发生的，您需要提供它，通常通过PropertyChangeSupport 提供，它可以帮助您管理PropertyChangeListeners 和触发事件...

通过将PropertyChangeListener 添加到JProgressBar，您正在监控它的变化，而不是您的框架。同样，通过在PropertyChangeListener 中修改JProgressBar 的状态，您可能会陷入无限循环，因为该对象会一遍又一遍地通知您您已经做出的更改... .

首先，你真的应该避免以这种方式使用static，最好有一个实例变量和一个setter来改变它的状态。您需要将框架的引用传递给那些对更改状态感兴趣的人，这引发了另一个问题，您真的不想不必要地公开您的程序元素，因此最好在一些中包含此功能一种界面，例如...

public interface Progressable {
    public void addPropertyChangeListener(PropertyChangeListener listener);
    public void removePropertyChangeListener(PropertyChangeListener listener);
    public void setInProgress(boolean inProgress);
    public boolean isInProgress();
}

然后你实现这个接口。然后Communicator 将引用this 接口的实例并根据需要调用setInProgress，例如...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JFrame;
import javax.swing.JProgressBar;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class MainFrame extends JFrame implements Progressable {

    private JProgressBar bar;
    public Communicator diplayFacade;
    private boolean inProgress;

    public MainFrame() {
        diplayFacade = new Communicator(this);
        bar = new JProgressBar();
        setLayout(new GridBagLayout());
        add(bar);
        addPropertyChangeListener("inProgress", new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                if (isInProgress()) {
                    bar.setIndeterminate(true);
                } else {
                    bar.setIndeterminate(false);
                }
            }
        });
    }

    @Override
    public void setInProgress(boolean value) {
        if (inProgress != value) {

            inProgress = value;
            firePropertyChange("inProgress", !inProgress, inProgress);

        }
    }

    @Override
    public boolean isInProgress() {
        return inProgress;
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException ex) {
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                } catch (UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new MainFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

Answer 2

这是可行的解决方案。感谢 MadProgrammer 的投入。必须添加 PropertyChangeSupport 以继续检查 inProgress 属性何时更改。

package progressbarPoc;

import java.awt.DisplayMode;
import java.awt.GridBagLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

import javax.swing.JFrame;
import javax.swing.JProgressBar;


public class MainFrame extends JFrame{

    public PropertyChangeSupport propertChangeSupport;
    public boolean inProgress;
    private JProgressBar bar;
    public Communicator diplayFacade;
    private PropertyChangeListener listener;
    public MainFrame() {
        this.setSize(500, 500);
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        diplayFacade = new Communicator();
        diplayFacade.frame = this;
        bar = new JProgressBar();
        setLayout(new GridBagLayout());
        add(bar);
        addProgressListener();
        propertChangeSupport = new PropertyChangeSupport(this);


        addListener();

        bar.addPropertyChangeListener(listener);
        this.addPropertyChangeListener(listener);
    }

    public void addPropertyChangeListener(PropertyChangeListener listener) {
        this.propertChangeSupport.addPropertyChangeListener(listener);
    }



    public void fireProperty(boolean oldValue , boolean newValue){
        this.propertChangeSupport.firePropertyChange("inProgress", oldValue, newValue);
    }

    public void addProgressListener(){

        System.out.println("Here");





    }

    public static void main(String[] args) {
        MainFrame frame = new MainFrame();
        frame.diplayFacade.methodCalled();


    }


    public void addListener(){


        listener = new PropertyChangeListener() {

            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                addPropertyChangeListener(this);
                if(true == inProgress){
                    System.out.println("Property change check none" + true);
                    bar.setIndeterminate(true);
                }
                else if(false ==inProgress){
                    System.out.println("Property change check none" + false);
                    bar.setIndeterminate(false);

                }

            }
        };
    }

}

还有 Communicator 类

package progressbarPoc;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

import javax.swing.JOptionPane;

public class Communicator {

    public MainFrame frame;

    public void methodCalled(){

        JOptionPane.showInputDialog("Hi");
        frame.inProgress = true;

        frame.fireProperty(frame.inProgress, !frame.inProgress);
    }

}