为什么这个属性更改()方法不能处理这个事件？

Question

我是Swing开发的新手，在使用实现PropertyChangeListener接口的类时遇到以下问题。

因此，我有以下GUI类（我只发布了这个类中有趣的部分）：

public class GUI extends SingleFrameApplication implements PropertyChangeListener {
private MainFrame mainFrame = null;
private static LoginFrame loginFrame;
    @Override
protected void startup() {
    boolean offLine = false;
            showLoginFrame();
    mainFrame = new MainFrame(settings, tasksSettings, logAppender);
    if (OSUtils.isUbuntuPrecisePangolin() || OSUtils.isFedoraBeefyMiracle() || OSUtils.isFedoraSphericalCow()) {
        File mountPointFolder = new File(System.getenv("HOME") + "/connect_drives");
        if (!mountPointFolder.exists())
            mountPointFolder.mkdir();
        mainFrame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        mainFrame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                if (mainFrame.getState() == JFrame.ICONIFIED)
                    tryToExit();
                else
                    mainFrame.setState(JFrame.ICONIFIED);
            }
        });
    }
}
private void showLoginFrame() {
    loginFrame = new LoginFrame();
    loginFrame.setVisible(true);
    loginFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    // Notify every change to every bound property for that object:
    loginFrame.addPropertyChangeListener(this); 
}
@Override
protected void shutdown() {
    System.out.println("Entered into GUI ---> shutdown()");
    logger.debug("Termino l'applicazione.");
    ulogger.info(Constants.APP_TITLE + "|Arresto "+ Constants.APP_TITLE);
    // FileUtils.saveGeneralLogFile(logAppender.getLogInFile());
    logAppender.saveGeneralLogFile();
    EventBusService.unsubscribe(this);
    if (mainFrame != null)
        mainFrame.setVisible(false);
}
public static void main(String[] args) {
    launch(GUI.class, args);
}
@Override
public void propertyChange(PropertyChangeEvent arg0) {
    System.out.println("GUI SingleFrameApplication ---> propertyChange(): " + arg0.getPropertyName());
    if (arg0.getPropertyName().equals("buttonLogOffClicked")) {
        //System.out.println("GUI SingleFrameApplication ---> richiamo exit");
        //exit();
        mainFrame.OnWindowClose();
        mainFrame.dispose();
        mainFrame = null;
        showLoginFrame();
    }
    if (arg0.getPropertyName().equals("loginResult")) {
        System.out.println("GUI SingleFrameApplication ---> richiamo MainFrame");
        //loginFrame.setVisible(false);
        loginFrame.dispose();
        loginFrame = null;
        showMainFrame();
    }
}
private void showMainFrame() {
    mainFrame = new MainFrame(settings, tasksSettings, logAppender);
    // I add a PropertyChangeListener to the created MainFrame object:
    mainFrame.addPropertyChangeListener(this);
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    WindowListener exitListener = new WindowAdapter() {
        @Override
        public void windowClosing(WindowEvent e) {
            System.out.println("GUI SingleFrameApplication --> windowClosing");
            shutdown();
            // mainFrame.setVisible(false);
            /*int confirm = JOptionPane.showOptionDialog(frame,
            "Are You Sure to Close this Application?",
            "Exit Confirmation", JOptionPane.YES_NO_OPTION,
            JOptionPane.QUESTION_MESSAGE, null, null, null);
            if (confirm == JOptionPane.YES_OPTION) {
            System.exit(1);
            }*/
        }
    };
    mainFrame.addWindowListener(exitListener);
    mainFrame.setVisible(true);
}

然后我有MainFram类，它扩展了JFrame，其中有一个JButton来执行注销操作，类似于以下内容：

public class MainFrame extends JFrame {
    private final Action actionLogOut = new AbstractAction() {
        {
            putValue(Action.NAME, _("log-out"));
        }
        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println("logOutButton clicked !!!, firePropertyChange() will start");
            // System.exit(0);
            firePropertyChange("buttonLogOffClicked", false, true);
        }
    };
    public MainFrame(Settings settings, TasksSettings tasksSettings, LogAppender logAppender) {
        super();
    ......................
    ......................
    ......................
    header.add(new JButton(actionLogOut));
    ......................
    ......................
    ......................
    }
}

因此，当我的JButton被点击时，它将按照以下方法执行：

private final Action actionLogOut = new AbstractAction() {
    {
        putValue(Action.NAME, _("log-out"));
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("logOutButton clicked !!!, firePropertyChange() will start");
        // System.exit(0);
        firePropertyChange("buttonLogOffClicked", false, true);
    }
};

实际上，当我点击控制台中的按钮时，我会看到输出：

"单击logOutButton！！，firePropertyChange（）将启动"

然后我执行firePropertyChange（）方法，我希望该事件由GUI类的方法处理：

@Override
public void propertyChange(PropertyChangeEvent arg0) {
    System.out.println("GUI SingleFrameApplication ---> propertyChange(): " + arg0.getPropertyName());
    if (arg0.getPropertyName().equals("buttonLogOffClicked")) {
        //System.out.println("GUI SingleFrameApplication ---> richiamo exit");
        //exit();
        mainFrame.OnWindowClose();
        mainFrame.dispose();
        mainFrame = null;
        showLoginFrame();
    }
    if (arg0.getPropertyName().equals("loginResult")) {
        System.out.println("GUI SingleFrameApplication ---> richiamo MainFrame");
        //loginFrame.setVisible(false);
        loginFrame.dispose();
        loginFrame = null;
        showMainFrame();
    }
}

但是不起作用，并且似乎没有进入firePropertyChange（）方法？

为什么？我错过了什么？

Tnx

Andrea

Answer 1

当您从MainFrame上下文调用firePropertyChange时，它正在为MainFrame触发，CCD_3实际上可以监听它的属性更改事件。但是您已经使用loginFrame.addPropertyChangeListener(this)向login frame添加了监听器；如果更改事件是由firePropertyChange函数触发的，则loginframe将侦听更改。但是，您可以拨打loginFrame.firePropertyChange("buttonLogOffClicked", false, true)；来自actionLogOut Action的actionPerformed()函数。

编辑：

1. 尝试将LoginFrame的实例传递给您创建的MainFrame实例构造函数。

2. 或者，在GUI类中声明一个名为fireLogInPropEvent的static函数。您需要将LoginFrame实例声明为静态实例。然后在这个函数中放入loginFrame.firePropertyChange("buttonLogOffClicked", false, true)来监听这个属性。

   public class GUI extends SingleFrameApplication implements PropertyChangeListener {
   
       private MainFrame mainFrame = null;
       private static LoginFrame loginFrame = new LoginFrame();
       /// your other code
       private void showLoginFrame() {
           // loginFrame = new LoginFrame(); <------- already created hence commenting out
           loginFrame.setVisible(true);
           loginFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           // Notify every change to every bound property for that object:
           loginFrame.addPropertyChangeListener(this); 
        }
         public static void fireLogInPropEvent()
         {
            loginFrame.firePropertyChange("buttonLogOffClicked", false, true);
         }
      }