Question

下面的示例允许显示，隐藏，处置和关闭窗口（通过发送事件）。

示例显示，该窗口仅打开一次 - 在第一组可见时。即使窗口被丢弃，然后再次显示，它也不会经历“开放”事件。

为什么？

如何在不编写处理程序并跟踪此事件的情况下知道窗口是否已打开？

如何关闭窗口以便在设置可见时再次进行打开事件？即如何将窗口对象返回初始状态？

是否还有其他可以拥有所需属性的州或事件？

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.AbstractAction;
import javax.swing.AbstractListModel;
import javax.swing.ComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.event.ListDataListener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Tester_JFrame_Closing_01 {

    private static Logger log = LoggerFactory.getLogger(Tester_JFrame_Closing_01.class);

    protected static Toolkit toolkit = Toolkit.getDefaultToolkit();
    protected static EventQueue eventQueue = toolkit.getSystemEventQueue();

    public static enum CloseOperation {

        DO_NOTHING_ON_CLOSE(JFrame.DO_NOTHING_ON_CLOSE),
        HIDE_ON_CLOSE(JFrame.HIDE_ON_CLOSE),
        DISPOSE_ON_CLOSE(JFrame.DISPOSE_ON_CLOSE),
        EXIT_ON_CLOSE(JFrame.EXIT_ON_CLOSE)
        ;

        public static ComboBoxModel newModel() {

            return new ComboBoxModel() {
                private CloseOperation selected = HIDE_ON_CLOSE;

                @SuppressWarnings("serial")
                private final AbstractListModel core = new AbstractListModel() {

                    @Override
                    public int getSize() {
                        return values().length;
                    }

                    @Override
                    public Object getElementAt(int index) {
                        return values()[index];
                    }

                };

                @Override
                public int getSize() {
                    return core.getSize();
                }

                @Override
                public Object getElementAt(int index) {
                    return core.getElementAt(index);
                }

                @Override
                public void addListDataListener(ListDataListener l) {
                    core.addListDataListener(l);
                }

                @Override
                public void removeListDataListener(ListDataListener l) {
                    core.removeListDataListener(l);
                }

                @Override
                public void setSelectedItem(Object anItem) {
                    selected = (CloseOperation) anItem;
                }

                @Override
                public Object getSelectedItem() {
                    return selected;
                }

            };

        }


        public final int Value;

        private CloseOperation(int value) {
            this.Value = value;
        }

        @Override
        public String toString() {
            switch(this) {
            case DISPOSE_ON_CLOSE:
                return "DISPOSE_ON_CLOSE";
            case HIDE_ON_CLOSE:
                return "HIDE_ON_CLOSE";
            case DO_NOTHING_ON_CLOSE:
                return "DO_NOTHING_ON_CLOSE";
            case EXIT_ON_CLOSE:
                return "EXIT_ON_CLOSE";
            default:
                return "<UNKNOWN>";
            }
        }
    }

    public static void main(String[] args) {

        WindowAdapter windowAdapter = new WindowAdapter() {
            @Override
            public void windowClosed(WindowEvent e) {
                log.debug("windowClosed");
            }

            @Override
            public void windowClosing(WindowEvent e) {
                log.debug("windowClosing");
            }

            @Override
            public void windowOpened(WindowEvent e) {
                log.debug("windowOpened");
            }

        };

        final JFrame frame = new JFrame("Controlled window");
        frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
        frame.addWindowListener(windowAdapter);

        final WindowEvent closeEvent = new WindowEvent(frame, WindowEvent.WINDOW_CLOSING);

        @SuppressWarnings("serial")
        AbstractAction closeAction = new AbstractAction("close") {
            @Override
            public void actionPerformed(ActionEvent e) {
                eventQueue.postEvent(closeEvent);
            }
        };

        @SuppressWarnings("serial")
        AbstractAction hideAction = new AbstractAction("hide") {
            @Override
            public void actionPerformed(ActionEvent e) {
                frame.setVisible(false);
            }
        };

        @SuppressWarnings("serial")
        AbstractAction showAction = new AbstractAction("show") {
            @Override
            public void actionPerformed(ActionEvent e) {
                frame.setVisible(true);
            }
        };

        @SuppressWarnings("serial")
        AbstractAction disposeAction = new AbstractAction("dispose") {

            @Override
            public void actionPerformed(ActionEvent e) {
                frame.dispose();
            }
        };

        JButton closeButton = new JButton(closeAction);
        JButton hideButton = new JButton(hideAction);
        JButton showButton = new JButton(showAction);
        JButton disposeButton = new JButton(disposeAction);

        ComboBoxModel closeOperationModel = CloseOperation.newModel();

        final JComboBox closeOperationCombo = new JComboBox(closeOperationModel);
        closeOperationCombo.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                log.debug("closeOperationCombo.actionPerformed({})", e);
                frame.setDefaultCloseOperation(((CloseOperation)closeOperationCombo.getSelectedItem()).Value);
            }
        });

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout());

        buttonPanel.add(showButton);
        buttonPanel.add(hideButton);
        buttonPanel.add(disposeButton);
        buttonPanel.add(closeButton);
        buttonPanel.add(closeOperationCombo);

        JFrame controlFrame = new JFrame("Controller window");
        controlFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        controlFrame.setLayout(new FlowLayout());
        controlFrame.add(buttonPanel, BorderLayout.SOUTH);
        controlFrame.pack();
        controlFrame.setLocation(100, 100);
        controlFrame.setVisible(true);

        frame.setBounds(100, 100 + controlFrame.getHeight(), controlFrame.getWidth(), 480);

    }
}

INCREDIBLE

他们有一个名为Window.state的字段，他们甚至没有初始化（因此它为零），然后他们在show()方法中测试一次并将其设置为1它是0。这是唯一使用state的地方，此处windowOpened被触发。没有代码可以将state返回0任何地方。此外，他们放弃了state子类中的Frame变量，并使用具有相同名称的新变量覆盖它，按位保存一些新状态，包括图标化和类似，并忘记打开的位！酷！

Answer 1

如何将窗口对象返回初始状态？

如果要将变量和组件返回到初始状态，那么我认为您需要重新创建窗口。

如何关闭窗口以便在设置可见时再次进行打开事件？

您可以通过以下方式跟踪窗口的关闭/打开：

    WindowAdapter windowAdapter = new WindowAdapter()
    {
        boolean closed = false;

        @Override
        public void windowClosed(WindowEvent e) {
            closed = true;
            System.out.println("windowClosed");
        }

        @Override
        public void windowClosing(WindowEvent e) {
            System.out.println("windowClosing");
        }

        @Override
        public void windowOpened(WindowEvent e) {
            System.out.println("windowOpened");
            closed = false;
        }

        @Override
        public void windowActivated(WindowEvent e) {
            System.out.println("windowActivated");

            if (closed)
                windowOpened(e);

        }
    };

要使“关闭”按钮起作用，您还需要使用：

    frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

Answer 2

您可以使用此

要在java swing应用程序中查找活动窗口（无论是框架还是对话框），您可以使用以下递归方法：

Window getSelectedWindow(Window[] windows) {
    Window result = null;
    for (int i = 0; i < windows.length; i++) {
        Window window = windows[i];
        if (window.isActive()) {
            result = window;
        } else {
            Window[] ownedWindows = window.getOwnedWindows();
            if (ownedWindows != null) {
                result = getSelectedWindow(ownedWindows);
            }
        }
    }
    return result;
}

参考这篇文章 Get current active window's title in Java

什么时候打开窗户？如何知道窗口打开没有监听窗口事件？

2 个答案: