java在许多片段中使用BroadcastReceiver

Question

我用的是一个有激光扫描仪的PDA。为此，我在许多片段中使用BroadcastReceiver。我有一个活动，它有一个BottomNavigationView在三个片段之间切换。我使用的BroadcastReceiver是这样的：

package com.example.package.fragments;


public class MyFragment extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";


    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;
    private final static String SCAN_ACTION = "scan.rcv.message";
    ScanDevice sm;


    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            //Doing my work
        }
    };

    public MyFragment () {
        // Required empty public constructor
    }

    public static MyFragment newInstance(String param1, String param2) {
        CarteGriseFragment fragment = new CarteGriseFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        sm = new ScanDevice();
        IntentFilter filter = new IntentFilter();
        filter.addAction(SCAN_ACTION);
        getContext().registerReceiver(mReceiver, filter);
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_carte_grise, container, false);

        return view;
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        sm = null;
        LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(mReceiver);
    }

    @Override
    public void onPause() {
        super.onPause();
        sm = null;
        LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(mReceiver);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
        sm = null;
        LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(mReceiver);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        sm = null;
        LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(mReceiver);
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        sm = null;
        LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(mReceiver);
    }

    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }

}

问题是，当我移动到另一个片段时，第一个片段的BroadcastReceiver在第二个片段中继续工作。事实上，当我在第二个片段中扫描某个东西时，第一个片段的BroadcastReceiver被调用。我搜索了许多解决方案，正如您在上面的代码中所看到的，我试图注销BroadcastReceiver，但没有成功

另一个片段的代码与上面的代码类似

Answer 1

我猜问题是在导航视图中，所有片段都处于可见状态，因此不调用onPause。当isVisibleToUser = false时，您可以尝试使用此方法setUserVisibleHint取消订阅

Answer 2

也许你可以使用RxJava

你说“我有一项活动”

像这样使用RxJava

在你的活动中，你只需要一个广播接收器。当触发“onReceive”函数时，请听它，然后用RxJava发送事件，并在片段中听这个事件