java - JNativeHook 和 swing - 为什么在 nativeKey* 方法中使用 runnable？

Question

我正在查看此网页上的最后一个示例 http://code.google.com/p/jnativehook/wiki/examples (发布在下面)

特别是nativeKeyReleased(NativeKeyEvent e)方法。我偶然发现了这一点，因为我在使用 swing 的应用程序中有时无法正确初始化 nativehook；因为我没有在 windowClosed() 方法中正确关闭它..

为什么需要在nativeKeyReleased(NativeKeyEvent e)中使用Runnable？

逐字记录:

import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import org.jnativehook.GlobalScreen;
import org.jnativehook.NativeHookException;
import org.jnativehook.keyboard.NativeKeyEvent;
import org.jnativehook.keyboard.NativeKeyListener;

public class SwingExample extends JFrame implements NativeKeyListener, WindowListener {
        public SwingExample() {
                setTitle("JNativeHook Swing Example");
                setSize(300, 150);
                setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
                addWindowListener(this);
                setVisible(true);
        }

        public void windowOpened(WindowEvent e) {
                //Initialze native hook.
                try {
                        GlobalScreen.registerNativeHook();
                }
                catch (NativeHookException ex) {
                        System.err.println("There was a problem registering the native hook.");
                        System.err.println(ex.getMessage());
                        ex.printStackTrace();

                        System.exit(1);
                }

                GlobalScreen.getInstance().addNativeKeyListener(this);
        }

        public void windowClosed(WindowEvent e) {
                //Clean up the native hook.
                GlobalScreen.unregisterNativeHook();
                System.runFinalization();
                System.exit(0);
        }

        public void windowClosing(WindowEvent e) { /* Unimplemented */ }
        public void windowIconified(WindowEvent e) { /* Unimplemented */ }
        public void windowDeiconified(WindowEvent e) { /* Unimplemented */ }
        public void windowActivated(WindowEvent e) { /* Unimplemented */ }
        public void windowDeactivated(WindowEvent e) { /* Unimplemented */ }

        public void nativeKeyReleased(NativeKeyEvent e) {
                if (e.getKeyCode() == NativeKeyEvent.VK_SPACE) {
                        SwingUtilities.invokeLater(new Runnable() {
                                public void run() {
                                        JOptionPane.showMessageDialog(null, "This will run on Swing's Event Dispatch Thread.");
                                }
                        });
                }
        }

        public void nativeKeyPressed(NativeKeyEvent e) { /* Unimplemented */ }
        public void nativeKeyTyped(NativeKeyEvent e) { /* Unimplemented */ }

        public static void main(String[] args) {
                 SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                                new SwingExample();
                        }
                });
        }
}

Answer 1

原因可能有很多。

主要原因是 native 钩子(Hook)可能使用自己的线程来监视输入。由于 Swing 是单线程框架，因此您需要将输出重新同步回该线程(又名事件调度线程)。

您可能还想避免阻塞 native 钩子(Hook)线程，以便它可以继续响应输入