java - 为什么这个 propertyChange() 方法无法处理这个事件？

Question

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

所以我有以下GUI类(我只发布该类中有趣的部分):

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);
}

然后我有一个MainFram类，它扩展了一个JFrame，其中有一个JButton来执行注销操作，如下所示:

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，当单击我的 JButton 时，将执行此方法:

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);
    }
};

事实上，当我单击按钮时，在控制台中，会出现输出:

“点击了 logOutButton!!!，firePropertyChange() 将启动”

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

@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

安德里亚

Answer 1

当您从 MainFrame 上下文调用 firePropertyChange 时，它会为 MainFrame 触发，它实际上可以监听其属性更改事件。但您已使用 loginFrame.addPropertyChangeListener(this) 将监听器添加到登录框架；如果更改事件由其自己的 firePropertyChange 函数触发，则 loginframe 将监听更改。但是您可以调用 loginFrame.firePropertyChange("buttonLogOffClicked", false, true);来自 MainFrame 类中 actionLogOut Action 的 actionPerformed() 函数。

编辑:

1. 尝试将 LoginFrame 实例传递给您已创建的用于使用的 MainFrame 实例构造函数。

2. 或者，在 GUI 类中声明一个名为 fireLogInPropEvent 的静态函数。您需要将您的 LoginFrame 实例声明为静态。然后在这个函数中放置 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);
         }
   
      }