public void CustomOnApplicationQuit()
 {
     Tello.onConnection -= Tello_onConnection;
     Tello.onUpdate     -= Tello_onUpdate;
     Tello.onVideoData  -= Tello_onVideoData;
     Tello.stopConnecting();
 }
 void OnApplicationQuit()
 {
     Tello.stopConnecting();
 }