Android : can't record audio via volume up button

im trying to create and app with a recording an audio and playing it. it currently has 2 buttons - 1 for recording and 1 for playing the last recorded sound. when im pressing the recording button it works perfect.

then, i tried to make it record by capturing the volume up button click.(wanted to make it record as long as the button is pressed).

when i try to record from the volume up button it throws me and IllegalStateException.

this is how i handle the click action on the volume up:

public boolean onKeyDown(int keyCode, KeyEvent event) {
 switch(keyCode){
   case KeyEvent.KEYCODE_VOLUME_UP:
     player.startRecording();
     return true;
 }
 return super.onKeyDown(keyCode, event);
}
public boolean onKeyUp(int keyCode, KeyEvent event) {
    switch(keyCode){
    case KeyEvent.KEYCODE_VOLUME_UP:
            player.stopRecording();
            return true;
        }

    return super.onKeyUp(keyCode, event);
}

thx in advance and sorry for the bad english