检查是否按下了Shift键 [英] Check whether shift key is pressed

问题描述

我正在编写一个应用程序，应在启动时检查是否按下了Shift键.为此，我创建了一个负责该工作的小类:

I'm programming an application which should, when started, check whether the shift key is pressed. For that I have created a small class which is responsible for that:

import java.awt.KeyEventDispatcher;
import java.awt.KeyboardFocusManager;
import java.awt.event.KeyEvent;

public class KeyboardListener {

    private static boolean isShiftDown;

    static {
        KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(
            new KeyEventDispatcher() {
                public boolean dispatchKeyEvent(KeyEvent e) {
                    isShiftDown = e.isShiftDown();
                    return false;
                }
            });
    }

    public static boolean isShiftDown() {
        return isShiftDown;
    }

}

但是，如果在应用程序启动时已经按了Shift键，这似乎不起作用.以下检查始终执行else情况.

However, it seems that this is not working if the shift key was already pressed when the application started up. The following check always executes the else case.

if (KeyboardListener.isShiftDown()) {
    // ...
} else {
    // this always gets executed
}

是否有一种方法可以检查在应用程序启动时是否已经按下了Shift键?我知道可以使用WinAPI，但是我更喜欢Javaish的方式.

Is there a way of checking whether the shift key is pressed if it was already pressed when the application started? I know this is possible using WinAPI, but I would prefer a Javaish way of doing it.

提前谢谢！

推荐答案

我将其描述为一种hack，但是它确实解决了该问题(有一些缺点)，因此我认为我将其作为一种可能性.

I'd characterize this as a hack, but it does solve the problem (with some downsides), so I figured I would mention it as a possibility.

您可以使用Robot类来模拟您的应用程序不关心的某些键(也许是功能键之一)的击键.注册KeyListener后立即运行此代码.您会看到一个按键事件，它将告诉您Shift是否关闭.

You can use the Robot class to simulate a keystroke of some key that your application doesn't care about (perhaps one of the function keys). Run this code right after you register your KeyListener. You'll see a key event which will tell you whether Shift is down.

警告:这将在系统中显示，就像用户实际按下并释放了F24(或您选择的任何键)一样.这可能会带来意想不到的副作用.

Warning: This will appear to the system as if the F24 (or whatever key you choose) had actually been pressed and released by the user. That could potentially have unexpected side-effects.

    (new Thread( )
    {
        @Override
        public void run( )
        {
            try
            {
                java.awt.Robot robot = new Robot();
                robot.delay( 100 );
                robot.keyPress( KeyEvent.VK_F24 );
                robot.keyRelease( KeyEvent.VK_F24 );
            }
            catch ( Exception e )
            {
            }
        }
    }).start( );

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