How can I write a key listener to track all keystrokes in Java? [closed]

Question

I want to write a key listener in Java. It should track all the key presses regardless of whether the Java app has focus or not. Is this possible?

Answer 1

It's possible but requires an implementation taking advantage of JNI which will not always be portable.

Java System Hook is one such library that will work with Windows 32 & 64 bit.

Answer 2

I used something like that a while ago. Take a look at Java System Hook.

It tracks global key presses (not just your Java application) via JNI. It worked fast and perfectly for me

---

The KeyListener starts as a daemon thread, which does not keep the application alive. You have to have another running non-daemon thread in your program

For example:

GlobalKeyListener globalKeyListener = new GlobalKeyListener();
globalKeyListener.addKeyListener(listener);
while (true) {
    Thread.sleep(1000);
}

Answer 3

No, Java does not have access to key-strokes outside of its active window.

To achieve this, you would have to use a combination of Java and native code, using JNI to call the native code. In Microsoft Windows, you should look at GetAsyncKeyState(key).

Answer 4

It's very much possible, but not using standard Java, you have to interact with the operating system on a native level.

Here is a topic for Windows that uses JNA to access the SetWindowsHookEx function in the Windows User32 API.

Answer 5

No, Java does not listen to keystokes if it's not active (focused) window, so you cannot do that.