A JNativeHook example in Scala

I’ve been working on a few applications where I want to get access to native, global keystrokes and mouse movements, so I’ve been using the JNativeHook library, which seems to work well on Mac OS X systems. I’ve been using Scala for all my coding the last few years instead of Java, so here’s a quick Scala port of the JNativeHook GlobalMouseListenerExample:

package jnativehookexample

import org.jnativehook.GlobalScreen
import org.jnativehook.NativeHookException
import org.jnativehook.mouse.NativeMouseEvent
import org.jnativehook.mouse.NativeMouseInputListener

class GlobalMouseListenerExample extends NativeMouseInputListener {

    def nativeMouseClicked(e: NativeMouseEvent) {
        println(s"Mouse Clicked: ${e.getClickCount}")
    }

    def nativeMousePressed(e: NativeMouseEvent) {
        println(s"Mouse Pressed: ${e.getButton}")
    }

    def nativeMouseReleased(e: NativeMouseEvent) {
        println(s"Mouse Released: ${e.getButton}")
    }

    def nativeMouseMoved(e: NativeMouseEvent) {
        println(s"Mouse Moved: ${e.getX}, ${e.getY}")
    }

    def nativeMouseDragged(e: NativeMouseEvent) {
        println(s"Mouse Dragged: ${e.getX}, ${e.getY}")
    }

}

object GlobalMouseListenerExample extends App {

    try {
        GlobalScreen.registerNativeHook
    } catch {
        case ex: NativeHookException =>
            System.err.println("There was a problem registering the native hook.")
            System.err.println(ex.getMessage)
            System.exit(1)
    }

    //construct the example object
    val example = new GlobalMouseListenerExample

    //add the appropriate listeners for the example object
    GlobalScreen.getInstance.addNativeMouseListener(example)
    GlobalScreen.getInstance.addNativeMouseMotionListener(example)
}

I just realized that I didn’t change the println statements initially, so I just updated those to use string interpolation. If I didn’t make any mistakes in changing those, the rest of the code should work fine. To run the example you’ll need to use the JNativeHook library and its dependencies.

Note: For your application to work properly on Mac OS X systems, you need to enable “access for assistive devices” for your application. On Mac OS X 10.9, that setting is under System Preferences > Security & Privacy > Privacy tab > Accessibility > Your Application.