尝试使用JAVA读取滚动锁定状态 [英] Trying to read Scroll Lock status using JAVA

问题描述

我有以下几行代码，试图读取滚动锁的状态.

I have the below lines of code using which i am trying to read status of scroll lock.

我的程序启动时获得滚动锁定的状态. 但是我愿意实时获取状态. 请在下面进行指导

I get the status of scroll lock when my program starts. However i am willing to get the status realtime. Please guide on the below

package assignment;

import java.awt.Toolkit;
import java.awt.event.KeyEvent;

import org.omg.PortableServer.THREAD_POLICY_ID;

public class ScrollLockOnOff {

    public static void main(String[] args) throws InterruptedException 
    {
        while(true)
        {
            Thread.sleep(1000);
            Toolkit toolkit=Toolkit.getDefaultToolkit();
            System.out.println(toolkit.getLockingKeyState(KeyEvent.VK_SCROLL_LOCK));
        }
    }

}

推荐答案

这是一个有趣的行为，它可以正确地报告初始状态，但要依赖后续事件处理(具有集中的顶层窗口或任务栏图标)来进行更新.

It’s an interesting behavior, to correctly report the initial state but to depend on subsequent event processing (having a focused top level window or tray icon) for updates.

如果我们有办法将AWT重置为其初始状态，它应该可以解决此问题.如果我们找不到这种可能性，那么直接的解决方法是运行一个新的JVM.由于具有相同属性的新JVM将使用高速缓存甚至共享内存中的资源，因此开销听起来要小得多.每秒执行一次操作没问题:

If we had a way to reset the AWT to its initial state, it should solve the issue. If we don’t find such a possibility, the straight-forward fix is to run a new JVM. Since a new JVM with the same properties will use resources in cache or even shared memory, the overhead is much smaller as it may sound. Performing the action once a second is no problem:

public class ScrollLockOnOff {
    public static void main(String[] args)
                       throws InterruptedException, AWTException, IOException {

        if(args.length == 1 && args[0].equals("VK_SCROLL_LOCK")) {
            System.exit(Toolkit.getDefaultToolkit()
                .getLockingKeyState(KeyEvent.VK_SCROLL_LOCK)? KeyEvent.VK_SCROLL_LOCK: 0);
            return;
        }

        ProcessBuilder b = new ProcessBuilder(
            Paths.get(System.getProperty("java.home"), "bin", "java").toString(),
            "-classpath", System.getProperty("java.class.path"),
            ScrollLockOnOff.class.getName(), "VK_SCROLL_LOCK"
        ).inheritIO();

        while(true) {
            Thread.sleep(1000);
            int state = b.start().waitFor();
            if(state != 0 && state != KeyEvent.VK_SCROLL_LOCK) {
                System.err.println("failed");
                break;
            }
            System.out.println(state == KeyEvent.VK_SCROLL_LOCK);
        }
    }
}

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