如何在java的后台运行这个关键监听器

Posted 2023-03-17

【中文标题】如何在java的后台运行这个关键监听器

【英文标题】：how to run this key listener in background in java

【发布时间】：2021-06-29 07:22:29

【问题描述】：

如何在后台运行这个关键监听器？我应该在代码部分嵌入什么？代码在前窗口中运行良好，但是当我切换到另一个窗口时 失去其功能。

import java.util.*;
import javax.imageio.*;
import java.awt.*;
import javax.swing.*; 

public class KeyListenerExample extends Frame implements KeyListener 
    Label l;  
    TextArea area;  

    KeyListenerExample() 
        l=new Label();  
        l.setBounds(20,50,100,20);  
        area=new TextArea();  
        area.setBounds(20,80,300, 300);  
        area.addKeyListener(this);

        add(l);add(area);  
        setSize(400,400);  
        setLayout(null);  
        setVisible(true); 
    

    public void keyPressed(KeyEvent e) 
        l.setText("Key Pressed");
    

    public void keyReleased(KeyEvent e) 
        l.setText("Key Released");
    

    public void keyTyped(KeyEvent e) 
        l.setText("Key Typed");
    

    public static void main(String[] args) 
        new KeyListenerExample();
    

【问题讨论】：

您是说即使您的应用程序不是焦点应用程序，您也希望您的应用程序继续捕获按键？

如果 Frame 在后台，它不会收到按键。

Java key listener to track all keystrokes的可能重复

【参考方案1】：

您可以使用 JNativeHook Java 库，即使您不在窗口中，它也会抓取密钥，这里是 JNativehook 的示例代码。来自我的一个较旧的项目。如果没有清除，请随时提出问题，您将需要下载 JNativeHook jar 文件

import java.awt.EventQueue;
import java.awt.Toolkit;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JDialog;
import javax.swing.JFrame;
import org.jnativehook.GlobalScreen;
import org.jnativehook.NativeHookException;
import org.jnativehook.keyboard.NativeKeyEvent;
import org.jnativehook.keyboard.NativeKeyListener;

public class Main2 extends JDialog implements NativeKeyListener 

    private static final long serialVersionUID = 1L;

    public static void main(String[] args) throws Exception 

        EventQueue.invokeLater(new Runnable() 
            @Override
            public void run() 
                try 

                    Main2 frame = new Main2(new JFrame() 
                        @Override
                        public boolean isShowing() 
                            return true;
                        
                    );
                 catch (Exception e) 
                    e.printStackTrace();
                
            
        );
    

    /**
     * Create the frame.
     * 
     * @throws IOException
     */
    public Main2(JFrame jFrame) throws IOException, NativeHookException 
        System.setProperty("sun.java2d.noddraw", "true");
        setBounds(0, 0, 1, 1);

        setUndecorated(true);
        this.setLocationRelativeTo(null);

        try 
            SwingExecutorService ses = new SwingExecutorService();
            GlobalScreen.getInstance().setEventDispatcher(ses);
            GlobalScreen.registerNativeHook();
            Logger loggy = Logger.getLogger(GlobalScreen.class.getPackage().getName());
            loggy.setLevel(Level.SEVERE);
         catch (Exception e) 

        

        GlobalScreen.getInstance().addNativeKeyListener(this);

        setFocusable(true);
        setVisible(true);

    

    @Override
    public void nativeKeyPressed(NativeKeyEvent e) 
        char ch = e.getKeyChar();
        System.out.println(e.getKeyText(e.getKeyCode()));
        int key = e.getKeyCode();
        System.out.println(ch);
        System.out.println(key);
        String modifiers = e.getModifiersText(e.getModifiers());
        int rawCode = e.getRawCode();
        System.out.println(rawCode);
    

    @Override
    public void nativeKeyTyped(NativeKeyEvent e) 
    

    private class SwingExecutorService extends AbstractExecutorService 
        private EventQueue queue;

        public SwingExecutorService() 
            queue = Toolkit.getDefaultToolkit().getSystemEventQueue();
        

        @Override
        public void shutdown() 
            queue = null;
        

        @Override
        public List<Runnable> shutdownNow() 
            return new ArrayList<>(0);
        

        @Override
        public boolean isShutdown() 
            return queue == null;
        

        @Override
        public boolean isTerminated() 
            return queue == null;
        

        @Override
        public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException 
            return true;
        

        @Override
        public void execute(Runnable r) 
            EventQueue.invokeLater(r);
        
    

    @Override
    public void nativeKeyReleased(NativeKeyEvent arg0) 
    

【参考方案2】：

如果这个另一个窗口也和第一个窗口在同一个java进程中运行，你可以使用

KeyboardFocusManager.addKeyEventDispatcher(java.awt.KeyEventDispatcher)

使用您的自定义 KeyEvenDispatcher