Java AWT 图形界面编程事件处理机制 ② ( Frame 窗口事件监听器 WindowListener | 代码示例 )

Posted 2023-02-01 韩曙亮

文章目录

• 一、Frame 窗口事件监听器 WindowListener
• 二、Frame 窗口事件监听器 WindowListener 代码示例

一、Frame 窗口事件监听器 WindowListener

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在 AWT 中 , 为 Frame 窗口 添加 窗口事件监听器 WindowListener , 可以监听窗口的操作 , 如 :

• 窗口显示 WindowListener#windowOpened(WindowEvent e)
• 窗口正在被关闭 WindowListener#windowClosing(WindowEvent e)
• 窗口完全关闭 WindowListener#windowClosed(WindowEvent e)
• 窗口最小化 WindowListener#windowIconified(WindowEvent e)
• 窗口从最小化开始改变 WindowListener#windowDeiconified(WindowEvent e)
• 窗口获取焦点 WindowListener#windowActivated(WindowEvent e)
• 窗口失去焦点 WindowListener#windowDeactivated(WindowEvent e)

Frame 窗口事件监听器 WindowListener 原型 : 可以阅读下面的原型中的文档 , 理解窗口的各种监听 ;

/**
 * The listener interface for receiving window events.
 * The class that is interested in processing a window event
 * either implements this interface (and all the methods it
 * contains) or extends the abstract <code>WindowAdapter</code> class
 * (overriding only the methods of interest).
 * The listener object created from that class is then registered with a
 * Window using the window's <code>addWindowListener</code>
 * method. When the window's status changes by virtue of being opened,
 * closed, activated or deactivated, iconified or deiconified,
 * the relevant method in the listener object is invoked, and the
 * <code>WindowEvent</code> is passed to it.
 *
 * @author Carl Quinn
 *
 * @see WindowAdapter
 * @see WindowEvent
 * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/windowlistener.html">Tutorial: How to Write Window Listeners</a>
 *
 * @since 1.1
 */
public interface WindowListener extends EventListener 
    /**
     * Invoked the first time a window is made visible.
     */
    public void windowOpened(WindowEvent e);

    /**
     * Invoked when the user attempts to close the window
     * from the window's system menu.
     */
    public void windowClosing(WindowEvent e);

    /**
     * Invoked when a window has been closed as the result
     * of calling dispose on the window.
     */
    public void windowClosed(WindowEvent e);

    /**
     * Invoked when a window is changed from a normal to a
     * minimized state. For many platforms, a minimized window
     * is displayed as the icon specified in the window's
     * iconImage property.
     * @see java.awt.Frame#setIconImage
     */
    public void windowIconified(WindowEvent e);

    /**
     * Invoked when a window is changed from a minimized
     * to a normal state.
     */
    public void windowDeiconified(WindowEvent e);

    /**
     * Invoked when the Window is set to be the active Window. Only a Frame or
     * a Dialog can be the active Window. The native windowing system may
     * denote the active Window or its children with special decorations, such
     * as a highlighted title bar. The active Window is always either the
     * focused Window, or the first Frame or Dialog that is an owner of the
     * focused Window.
     */
    public void windowActivated(WindowEvent e);

    /**
     * Invoked when a Window is no longer the active Window. Only a Frame or a
     * Dialog can be the active Window. The native windowing system may denote
     * the active Window or its children with special decorations, such as a
     * highlighted title bar. The active Window is always either the focused
     * Window, or the first Frame or Dialog that is an owner of the focused
     * Window.
     */
    public void windowDeactivated(WindowEvent e);

二、Frame 窗口事件监听器 WindowListener 代码示例

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代码示例 :

import java.awt.*;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class HelloAWT 
    private Frame frame;

    private void init() 
        frame = new Frame("AWT 界面编程");

        frame.addWindowListener(new WindowListener() 
            @Override
            public void windowOpened(WindowEvent e) 
                System.out.println("窗口打开");
            

            @Override
            public void windowClosing(WindowEvent e) 
                System.out.println("窗口正在关闭");
                System.exit(0);
            

            @Override
            public void windowClosed(WindowEvent e) 
                System.out.println("窗口完全关闭");
            

            @Override
            public void windowIconified(WindowEvent e) 
                System.out.println("窗口最小化");
            

            @Override
            public void windowDeiconified(WindowEvent e) 
                System.out.println("窗口从最小化开始变化");
            

            @Override
            public void windowActivated(WindowEvent e) 
                System.out.println("窗口获取焦点");
            

            @Override
            public void windowDeactivated(WindowEvent e) 
                System.out.println("窗口失去焦点");
            
        );

        frame.pack();
        frame.setVisible(true);
    

    public static void main(String[] args) 
        new HelloAWT().init();
    

执行结果 :

窗口显示时 , 自动回调 windowActivated 先获取焦点 , 然后回调 windowOpened 函数 说明获取了焦点 ,

点击最小化按钮 , 会自动回调 windowIconified 函数 , 然后回调 windowDeactivated 函数 说明失去了焦点 ,

然后点击底部图标的程序图标 , 将其展示到前台 , 会自动回调 windowDeiconified 函数 , 然后自动回调 windowActivated 函数 , 说明获取了焦点 ;

最后点击 关闭按钮 , 会回调 windowClosing 函数 , 此时直接退出了程序 ;