How to detect input data through the audio jack?

Question

I know that some devices headphone ports (maybe all of them? any reference here would be good) have 3 channels, for stereo sound and microphone. So I was wondering if it\'s poss

Answer 1

I finally managed to read the pedal input. @emrys57 is right, replacing the jack with the 4-pin connector, triggered the input the same way microphones with a hook button do. However occasionally it seems to trigger the volume up and the volume down keys as well. I suppose this is related to me replacing the 4-pin jack with a knife and tape.

It was fairly simple to override onKeyUp. Be aware that you also have to override onKeyDown to prevent the default behavior:

@Override
public boolean onKeyDown(int keyCode,KeyEvent event){
    int action = event.getAction();
    if (keyCode == KeyEvent.KEYCODE_VOLUME_UP
            || keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
            || keyCode == KeyEvent.KEYCODE_HEADSETHOOK) {

        if (action == KeyEvent.ACTION_UP) {
            Log.d(TAG, "action_up");
            clickStart(null);
            return true;
        } else if (action == KeyEvent.ACTION_DOWN) {
            Log.d(TAG, "action_down");
            return true;
        } else {
            Log.d(TAG, "action:" + action);
            return true;
        }
    }
    return false;
}

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
    int action = event.getAction();
    Log.d(TAG, "onKeyDown!");
    if (keyCode == KeyEvent.KEYCODE_VOLUME_UP
            || keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
            || keyCode == KeyEvent.KEYCODE_HEADSETHOOK) {

        if (action == KeyEvent.ACTION_UP) {
            Log.d(TAG, "action_up");
            clickStart(null);
            return true;
        } else if (action == KeyEvent.ACTION_DOWN) {
            Log.d(TAG, "action_down");
            return false;
        } else {
            Log.d(TAG, "action:" + action);
            return true;
        }
    }
    if (keyCode == KeyEvent.KEYCODE_BACK) {         
        finish();
        return true;
    }
    Log.d(TAG, "returning false");
    return false;
}