Java 当JComponent不再可见时，是否有方法从集合中删除UCASE父对象以获取通知？

假设我有一个简单的JFrame，其中一个JTabbedPane包含3个面板，第二个面板包含一个JComponent。当“Tab 2”面板从其容器中移除时，是否有一种方法通知JComponent？我的问题是JComponent可能在层次结构中很深

显然，我在这里寻找SWING解决方案…：）

我试着用（）来做这件事，但运气不好。。。我显然做错了什么

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另外，ASCII艺术是由。

我将使用

ComponentListener

来完成这项工作（

CardLayout

非常接近，与

JTabbedPane

类似），代码示例包含所有相关的侦听器（免责声明-->注意阻止EDT仅作为代码示例使用，并且仅以这种形式使用）

Ancesor&HierarchyListener

是有点异步的，从

AncestorListener

---

多亏了mKorbel's发布了一个很好的例子，他使用了HierarchyListener，我想出了一个我认为可以满足我需求的解决方案。在本例中，我使用

JLabel

作为需要通知的组件

我会接受mKorbel的回答，因为他为我节省了很多时间

代码如下：

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.event.AncestorEvent;
import javax.swing.event.AncestorListener;
import javax.swing.JTabbedPane;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.HierarchyEvent;
import java.awt.event.HierarchyListener;

public class TestFrame extends JFrame {
    private static final long serialVersionUID = 8388031406846751884L;
    private JPanel contentPane;
    private JTabbedPane tabbedPane;
    private JLabel label; /// The component that needs to be notified when it should save its states.

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    TestFrame frame = new TestFrame();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Adds necessary listeners.
     * @param argLabel
     */
    private void install(JLabel argLabel) {
        // ::::: HierarchyListener ::::::::::::::::::::::::::::::::::::::::::::::::::::::::
        argLabel.addHierarchyListener(new HierarchyListener() {
            @Override
            public void hierarchyChanged(HierarchyEvent arg0) {
                if ((arg0.getChangeFlags() & HierarchyEvent.DISPLAYABILITY_CHANGED) != 0) {
                    if (!arg0.getComponent().isDisplayable()) {
                        // component is not displayable due to the panel being removed
                        doSomething();
                    }
                }
            } 
        });

        // ::::: AncestorListener :::::::::::::::::::::::::::::::::::::::::::::::::::::::::
        argLabel.addAncestorListener(new AncestorListener() {

            @Override
            public void ancestorAdded(AncestorEvent arg0) {
                // not interested in this one
            }

            @Override
            public void ancestorMoved(AncestorEvent arg0) {
                // not interested in this one
            }

            @Override
            public void ancestorRemoved(AncestorEvent arg0) {
                // ancestorRemoved() is useful when user navigates between tabs, and causes
                // component to become invisible.
                doSomething();
            } 
        });
    }

    public void doSomething() {
        System.out.println("Saving some state(s)...");
    }

    /**
     * Create the frame.
     */
    public TestFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 693, 376);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        tabbedPane = new JTabbedPane(JTabbedPane.TOP);
        // first panel
        tabbedPane.add(new JPanel()); 
        // second panel
        JPanel panelWithComponents = new JPanel();
        JPanel childPanel = new JPanel();
        label = new JLabel("Test label");
        install(label);
        childPanel.add(label);
        panelWithComponents.add(childPanel);
        tabbedPane.add(childPanel);
        // third panel
        tabbedPane.add(new JPanel());

        contentPane.add(tabbedPane, BorderLayout.CENTER);

        JButton btnRemove = new JButton("Remove second");
        btnRemove.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                tabbedPane.remove(1);
            }
        });
        contentPane.add(btnRemove, BorderLayout.SOUTH);
    } // main() method

} // TestFrame class

---

如果组件本身需要执行某些操作，您还可以覆盖add/removeNotify（不过不要忘记调用super）

import java.awt.*;
import java.awt.event.*;
import java.util.Date;
import javax.swing.*;

public class LabelWithTimer extends JLabel {

    private final Timer timer;

    public LabelWithTimer() {
        timer = new Timer(1000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                setText(new Date().toString());
            }
        });
    }

    @Override
    public void addNotify() {
        super.addNotify();
        timer.start();
        System.out.println("Clock started");
    }

    @Override
    public void removeNotify() {
        System.out.println("Clock stopped");
        timer.stop();
        super.removeNotify();
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                final JPanel clock = new JPanel(new GridBagLayout());
                clock.add(new LabelWithTimer());

                final JTabbedPane tabs = new JTabbedPane();
                tabs.addTab("Empty", new JLabel());
                tabs.setPreferredSize(new Dimension(400, 300));

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(tabs);
                frame.getContentPane().add(new JButton(new AbstractAction("Add/remove clock") {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if(tabs.getTabCount() == 2) {
                            tabs.removeTabAt(1);
                        }
                        else {
                            tabs.addTab("Clock", clock);
                            tabs.setSelectedIndex(1);
                        }

                    }
                }), BorderLayout.PAGE_END);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}

---

这个场景可以通过

antestorremoved（）来处理

。当用户选择其他JTabbedPane的子组件时，该组件将获得该事件。问题是，当包含该组件的JTabbedPane的子组件被删除时……看起来唯一得到通知的方法是使用ContainerListener或适配器……感谢mKorbel，我所需要的只是当用户删除该组件时的HierarchyListener专家组：）

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.event.AncestorEvent;
import javax.swing.event.AncestorListener;
import javax.swing.JTabbedPane;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.HierarchyEvent;
import java.awt.event.HierarchyListener;

public class TestFrame extends JFrame {
    private static final long serialVersionUID = 8388031406846751884L;
    private JPanel contentPane;
    private JTabbedPane tabbedPane;
    private JLabel label; /// The component that needs to be notified when it should save its states.

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    TestFrame frame = new TestFrame();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Adds necessary listeners.
     * @param argLabel
     */
    private void install(JLabel argLabel) {
        // ::::: HierarchyListener ::::::::::::::::::::::::::::::::::::::::::::::::::::::::
        argLabel.addHierarchyListener(new HierarchyListener() {
            @Override
            public void hierarchyChanged(HierarchyEvent arg0) {
                if ((arg0.getChangeFlags() & HierarchyEvent.DISPLAYABILITY_CHANGED) != 0) {
                    if (!arg0.getComponent().isDisplayable()) {
                        // component is not displayable due to the panel being removed
                        doSomething();
                    }
                }
            } 
        });

        // ::::: AncestorListener :::::::::::::::::::::::::::::::::::::::::::::::::::::::::
        argLabel.addAncestorListener(new AncestorListener() {

            @Override
            public void ancestorAdded(AncestorEvent arg0) {
                // not interested in this one
            }

            @Override
            public void ancestorMoved(AncestorEvent arg0) {
                // not interested in this one
            }

            @Override
            public void ancestorRemoved(AncestorEvent arg0) {
                // ancestorRemoved() is useful when user navigates between tabs, and causes
                // component to become invisible.
                doSomething();
            } 
        });
    }

    public void doSomething() {
        System.out.println("Saving some state(s)...");
    }

    /**
     * Create the frame.
     */
    public TestFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 693, 376);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        tabbedPane = new JTabbedPane(JTabbedPane.TOP);
        // first panel
        tabbedPane.add(new JPanel()); 
        // second panel
        JPanel panelWithComponents = new JPanel();
        JPanel childPanel = new JPanel();
        label = new JLabel("Test label");
        install(label);
        childPanel.add(label);
        panelWithComponents.add(childPanel);
        tabbedPane.add(childPanel);
        // third panel
        tabbedPane.add(new JPanel());

        contentPane.add(tabbedPane, BorderLayout.CENTER);

        JButton btnRemove = new JButton("Remove second");
        btnRemove.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                tabbedPane.remove(1);
            }
        });
        contentPane.add(btnRemove, BorderLayout.SOUTH);
    } // main() method

} // TestFrame class

import java.awt.*;
import java.awt.event.*;
import java.util.Date;
import javax.swing.*;

public class LabelWithTimer extends JLabel {

    private final Timer timer;

    public LabelWithTimer() {
        timer = new Timer(1000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                setText(new Date().toString());
            }
        });
    }

    @Override
    public void addNotify() {
        super.addNotify();
        timer.start();
        System.out.println("Clock started");
    }

    @Override
    public void removeNotify() {
        System.out.println("Clock stopped");
        timer.stop();
        super.removeNotify();
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                final JPanel clock = new JPanel(new GridBagLayout());
                clock.add(new LabelWithTimer());

                final JTabbedPane tabs = new JTabbedPane();
                tabs.addTab("Empty", new JLabel());
                tabs.setPreferredSize(new Dimension(400, 300));

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(tabs);
                frame.getContentPane().add(new JButton(new AbstractAction("Add/remove clock") {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        if(tabs.getTabCount() == 2) {
                            tabs.removeTabAt(1);
                        }
                        else {
                            tabs.addTab("Clock", clock);
                            tabs.setSelectedIndex(1);
                        }

                    }
                }), BorderLayout.PAGE_END);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}