How do I check if the caps lock key is pressed?

Question

Alright, before this gets flagged as a possible duplicate, I\'ve already tried the following code:

Toolkit.getDefaultToolkit().getLockingKeyState(KeyEvent.VK         


        

Answer 1

Poking around, I think getLockingKeyState() might be broken.

You could try KeyboardUtils, but it looks like that means you have to carry JNA overhead.

Answer 2

public void checkOnOff() {
    Thread th = new Thread() {
        public void run() {
            for (;;) {
                if (Toolkit.getDefaultToolkit().getLockingKeyState(KeyEvent.VK_CAPS_LOCK)) {
                    jLabel4.setForeground(Color.red);
                    jLabel4.setText("CAPSLOCK is ON");
                } else {
                    jLabel4.setText(null);
                }
                try {
                    sleep(100);
                } catch (InterruptedException ex) {
                    Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
                }                    
            }
        }
    };th.start();
}

Answer 3

Looks like this was always broken or at least since Java 1.3 (see Bug 4414164).

Not sure for other platforms, but for Windows I can say this: State change of Caps Lock can be detected, but only if your awt client has the focus. However, there is this workaround which works for me:

boolean isCapsLockOn() {
    java.awt.Robot robot = new java.awt.Robot();
    robot.keyPress(KeyEvent.VK_CONTROL);
    robot.keyRelease(KeyEvent.VK_CONTROL);
    return Toolkit.getDefaultToolkit().getLockingKeyState(KeyEvent.VK_CAPS_LOCK);  
}

Contraint: Your awt app must have the focus before calling isCapsLockOn.

Note: Your robot might press any other key which is not harmful to your app. Might depend on your use case.