Is it possible to create an Android Service that listens for hardware key presses?

Question

I'd like to run an Android background service that will act as a keylistener from the home screen or when the phone is asleep. Is this possible?

From semi-related examples online, I put together the following service, but get the error, "onKeyDown is undefined for the type Service". Does this mean it can't be done without rewriting Launcher, or is there something obvious I'm missing?

public class ServiceName extends Service {

    @Override
    public void onCreate() {
        //Stuff
    }

    public IBinder onBind(Intent intent) {
        //Stuff
        return null;
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(event.getAction() == KeyEvent.ACTION_DOWN) {
        switch(keyCode) {
        case KeyEvent.KEYCODE_A:
            //Stuff
            return true;
        case KeyEvent.KEYCODE_B:
            //Stuff
            return true;

            //etc.
        }
        }

        return super.onKeyDown(keyCode, event);
    }
}

I realize Android defaults to the search bar when you type from the home screen, but this really is just for a very particular use. I don't really expect anyone but me to want this. I just think it'd be nice, for example, to use the camera button to wake the phone.

Answer 1

As far as I know KeyEvents can only be handled by Activities as they are the interface to the user pressing the keys. Services run in the background and are not intended to react on user input. That's also the reason of your compiler warning "onKeyDown is undefined for the type Service". Service or any of it's Superclasses don't implement the KeyEvent.Callback interface. As a workaround you could register an Activity in your AndroidManifest.xml to react on certain system notifications such as android.intent.action.SCREEN_ON. When the power button is pressed to turn on the screen your activity could be started, initializing a service of some kind and go back to the background. If that's what you intend to do. See Intent docs for possible Actions.

Hope that helped...