Android 关闭飞行模式时应用程序崩溃

Question

I am building an application in which I have a Google Maps Fragment. In my MainActivity onCreate() method, I display this Google Maps Fragment which works fine in all cases except with airplane mode. If I turn airplane mode off while the application is running, my app crushes. I tried to include some Logs to see which methods are called and apparently, the following methods are called in order:

onPause() in MapFragment

onPause() in MainActivity

onCreate() in MainActivity

onResume() in MainActivity

and finally the app crushes in onMapReady(GoogleMap googleMap) in the MapFragment when I call

MapsInitializer.initialize(getActivity());

What I do not understand is how and why these methods are called when airplane mode is turned off and how to prevent the application from crushing.

Here is the stack trace of the error

2020-12-03 05:32:44.070 700-700/com.example.mutapamaps E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.mutapamaps, PID: 700
    java.lang.NullPointerException: Context is null
        at com.google.android.gms.common.internal.Preconditions.checkNotNull(com.google.android.gms:play-services-basement@@17.3.0:11)
        at com.google.android.gms.maps.MapsInitializer.initialize(Unknown Source)
        at com.example.mutapamaps.Fragments.MapFragment.onMapReady(MapFragment.java:218)
        at com.google.android.gms.maps.zzac.zza(Unknown Source)
        at com.google.android.gms.maps.internal.zzaq.dispatchTransaction(Unknown Source)
        at com.google.android.gms.internal.maps.zzb.onTransact(Unknown Source)
        at android.os.Binder.transact(Binder.java:504)
        at dt.aZ(:com.google.android.gms.dynamite_mapsdynamite@204516046@20.45.16 (040306-0):2)
        at com.google.maps.api.android.lib6.impl.bi.run(:com.google.android.gms.dynamite_mapsdynamite@204516046@20.45.16 (040306-0):1)
        at android.os.Handler.handleCallback(Handler.java:836)
        at android.os.Handler.dispatchMessage(Handler.java:103)
        at android.os.Looper.loop(Looper.java:203)
        at android.app.ActivityThread.main(ActivityThread.java:6251)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)

Here is my MainActivity

public class MainActivity extends AppCompatActivity{

    public static FragmentManager fragmentManager;
    public static final String LOG_TAG = "LOG_TAG";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.i(LOG_TAG, "Main activity created");
        super.onCreate(savedInstanceState);

        // init airplane mode receiver
        IntentFilter intentFilter = new IntentFilter(Intent.ACTION_AIRPLANE_MODE_CHANGED);
        BroadcastReceiver receiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {

                boolean isAirplaneModeOn = intent.getBooleanExtra("state", false);
                if(isAirplaneModeOn){
                    Log.i(LOG_TAG, "Airplane mode turned on");// handle Airplane Mode on
                } else {
                    Log.i(LOG_TAG, "Airplane mode turned off");
                }
            }
        };
        this.registerReceiver(receiver, intentFilter);


        setContentView(R.layout.activity_main);
        fragmentManager = getSupportFragmentManager();
        displayFragment(new MapFragment());
    }


    @Override
    protected void onPause() {
        super.onPause();
        Log.i(LOG_TAG, "Main activity paused");
    }


    @Override
    protected void onResume() {
        super.onResume();
        Log.i(LOG_TAG, "Main activity resumed");
    }


    public void displayFragment(Fragment fragmentActivity){

        // start the transaction
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container, fragmentActivity).
                    addToBackStack(fragmentActivity.getClass().getSimpleName()).commit();
    }
}

Here is my MapFragment

public class MapsFragment extends Fragment implements
        OnMapReadyCallback {


    public MapsFragment() {
        // Required empty public constructor
        super();
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_map, container, false);
    }


    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        FrameLayout map_frame = view.findViewById(R.id.map_frame);

        // configure map
        MapView mapFragment = view.findViewById(R.id.map_view);
        mapFragment.onCreate(savedInstanceState);
        mapFragment.onResume();
        mapFragment.getMapAsync(this);
        View mapView = mapFragment.getRootView();
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.i(LOG_TAG, "MapFragment resumed");
    }


    @Override
    public void onPause() {
        super.onPause();
        Log.i(LOG_TAG, "Map fragment paused");
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        Log.i(LOG_TAG, "onMapReadyCalled");
        MapsInitializer.initialize(getActivity());
    }
}

May you please help me understand what is going on and debug this piece of code.

Thank you in advance.

Answer 1

Change the onViewCreated with this part of code. Hope it helps.

@Override
 public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
 FrameLayout map_frame = view.findViewById(R.id.map_frame);

 // configure map
 MapView mapFragment = view.findViewById(R.id.map_view);
 mapFragment.onCreate(savedInstanceState);
 mapFragment.onResume();
 mapFragment.getMapAsync(this);
 View mapView = mapFragment.getRootView();
 super.onViewCreated(mapView , savedInstanceState);

}

Answer 2

Replace Your MapsFragment with this.

public class MapsFragment extends Fragment implements
    OnMapReadyCallback {

  Context context;


public MapsFragment() {
    // Required empty public constructor
    super();
}

    @Override
public void onAttach(Context context) {
    super.onAttach(context);
    this.context = context;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_map, container, false);
}


@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    FrameLayout map_frame = view.findViewById(R.id.map_frame);

    // configure map
    MapView mapFragment = view.findViewById(R.id.map_view);
    mapFragment.onCreate(savedInstanceState);
    mapFragment.onResume();
    mapFragment.getMapAsync(this);
    View mapView = mapFragment.getRootView();
    super.onViewCreated(view, savedInstanceState);
}

@Override
public void onResume() {
    super.onResume();
    Log.i(LOG_TAG, "MapFragment resumed");
}


@Override
public void onPause() {
    super.onPause();
    Log.i(LOG_TAG, "Map fragment paused");
}

@Override
public void onMapReady(GoogleMap googleMap) {
    Log.i(LOG_TAG, "onMapReadyCalled");
    MapsInitializer.initialize(context);
}

}