在 Fragment 中调用 Service 执行下载任务，但是失败了，代码如下，请问下是为什么啊

public class JokeFragment extends Fragment implements ServiceConnection, SendCallBack {

        private RecyclerView mRecyclerView;
        private RecyclerAdapter mAdapter;
        private List<JokeData> mJokeDatas = new ArrayList<>();
        private JokeService mService;

        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
        }

        @Override
        public void onActivityCreated(@Nullable Bundle savedInstanceState) {
                super.onActivityCreated(savedInstanceState);
                Intent intent = new Intent(getActivity().getApplicationContext(), JokeService.class);
                getActivity().getApplicationContext().bindService(intent, this, Context.BIND_AUTO_CREATE);
        }

        @Override
        public void onResume() {
                super.onResume();
                mAdapter.notifyDataSetChanged();
        }

        @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
                View view = inflater.inflate(R.layout.fragment_joke, container, false);
                mRecyclerView = (RecyclerView) view.findViewById(R.id.fragment_recyclerview);
                mAdapter = new RecyclerAdapter(getActivity(), mJokeDatas);
                mRecyclerView.setItemAnimator(new DefaultItemAnimator());
                mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
                mRecyclerView.setHasFixedSize(true);
                mRecyclerView.setAdapter(mAdapter);
                return view;
        }

        @Override
        public void onResult(List<JokeData> datas) {
                mJokeDatas = datas;
        }

        @Override
        public void onError(String info) {
        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
                mService = ((JokeService.LocalBinder) service).getService();
                if (mService!=null){
                        mService.setCallBack(this);
                        mService.Download();
                }

        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
                mService = null;
        }

        @Override
        public void onPause() {
                super.onPause();
                if (mService != null) {
                        mService.setCallBack(null);
                        getActivity().getApplicationContext().unbindService(this);
                }
        }
}

 if (mService != null) {
                    mService.setCallBack(null);
                    getActivity().getApplicationContext().unbindService(this);
            }

                            放 在OnDestory()中试试