我收到以下错误，我认为这意味着我的活动为空

fragment not attached to activity on volley response

我如何解决这个问题？这些是我的代码

  MainActivity._MainActivity_.runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(MainActivity._MainActivity_, "inserted", Toast.LENGTH_SHORT).show();
                        }
                    });
                   Activity activity = getActivity();
                   if(activity != null){
                        Intent mainIntent = new Intent(define, SaveNewFactor.class);
                        startActivity(mainIntent);
                    }else {
                        Log.i("myLog","activity is null");
                    }

我的logcat图像