当我使用 Retrofit 时，Google 位置服务返回一个空位置

Question

我有一个片段，我想在其中获取当前坐标，然后使用 Retrofit 向 Zomato Api 发出请求，但我当前的位置返回 null。我试图删除与我的 api 调用相关的代码，应用程序返回我正确的纬度和经度。我在做什么错？下面是我的 Java 类。

我的片段

public class RestaurantsList extends Fragment {
    private RestaurantAdapter mAdapter;
    private RecyclerView mRecyclerView;
    protected static List<Restaurant_> restaurantsList;
    private Context context;
    protected static OnRestaurantClickedListener listener;
    private FirebaseAuth mAuth;
    private static final int REQUEST_FINE_LOCATION=100;
    private LocationRequest mLocationRequest;
    private LocationCallback mLocationCallback;
    private FusedLocationProviderClient mFusedLocationClient;
    private Location myLocation;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = getContext();
        mAuth = FirebaseAuth.getInstance();
        restaurantsList= new ArrayList<>(50);
        getLastLocation();
        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(getActivity());


        mFusedLocationClient.getLastLocation().addOnSuccessListener(getActivity(), new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                if (location != null) {
                    myLocation=location;
                    Toast.makeText( getActivity(),"Latitude: "+location.getLatitude()+" Longitude: "+location.getLongitude(), Toast.LENGTH_SHORT).show();

                }
            }
        }).addOnFailureListener(getActivity(), new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText( getActivity(),"It wasn´t possible to determine your location", Toast.LENGTH_SHORT).show();
            }
        });

        getApi().getNearbyRestaurants(myLocation.getLatitude(),myLocation.getLongitude(),20,10000,"rating","desc","75be9f9e2239fe637bf9cb1b46979d91")
                .enqueue(new Callback<ApiResponse>() {
                    @Override
                    public void onResponse(Call<ApiResponse> call, Response<ApiResponse> response) {
                        List<Restaurant> restaurants=response.body().getRestaurants();
                       mAdapter = new RestaurantAdapter(context, restaurantsList);
                        mRecyclerView.setAdapter(mAdapter);
                        RecyclerView.ItemDecoration itemDecoration = new DividerItemDecoration(context, DividerItemDecoration.VERTICAL);
                        mRecyclerView.addItemDecoration(itemDecoration);
                       for (int i = 0; i < restaurants.size(); i++) {
                            restaurantsList.add(restaurants.get(i).getRestaurant());
                            mAdapter.notifyItemInserted(i);
                        }
                    }

                    @Override
                    public void onFailure(Call<ApiResponse> call, Throwable t) {
                        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                        builder.setMessage("Couldn´t find any nearby restaurants");
                        AlertDialog mDialog = builder.create();
                        mDialog.show();


                    }
                });
    }


    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View mContentView = inflater.inflate(R.layout.restaurants_list, container,false);
        mRecyclerView = mContentView.findViewById(R.id.recycler_view);

        mRecyclerView.setLayoutManager(new LinearLayoutManager(mContentView.getContext()));

        return mContentView;
    }

    @Override
    public void onResume() {
        super.onResume();


    }

    @Override public void onAttach(Activity activity) {
        super.onAttach(activity);
        try{
            listener= (OnRestaurantClickedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnButtonClicked");
        }
    }

    private Retrofit getRetrofit(){
        return new Retrofit.Builder()
                .baseUrl("https://developers.zomato.com/api/v2.1/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }

    private ZomatoApi getApi(){
        return  getRetrofit().create(ZomatoApi.class);
    }

    private void getLastLocation(){
        if (ActivityCompat.checkSelfPermission(getContext(),
                Manifest.permission.ACCESS_FINE_LOCATION )!= PackageManager.PERMISSION_GRANTED) {
            requestPermissions();
            return;

        }
    }

    private void requestPermissions(){
        ActivityCompat.requestPermissions(getActivity(),
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                REQUEST_FINE_LOCATION);
    }


}

新代码

public class RestaurantsList extends Fragment {
    private RestaurantAdapter mAdapter;
    private RecyclerView mRecyclerView;
    protected static List<Restaurant_> restaurantsList;
    private Context context;
    protected static OnRestaurantClickedListener listener;
    private FirebaseAuth mAuth;
    private static final int REQUEST_FINE_LOCATION=100;
    private LocationRequest mLocationRequest;
    private LocationCallback mLocationCallback;
    private FusedLocationProviderClient mFusedLocationClient;
    private static final String TAG = "LOCATION";


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = getContext();
        mAuth = FirebaseAuth.getInstance();
        restaurantsList= new ArrayList<>(50);
        getLastLocation();
        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(getActivity());
    }


    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View mContentView = inflater.inflate(R.layout.restaurants_list, container,false);
        mRecyclerView = mContentView.findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(mContentView.getContext()));

        return mContentView;
    }

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

    @Override public void onAttach(Activity activity) {
        super.onAttach(activity);
        try{
            listener= (OnRestaurantClickedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnButtonClicked");
        }
    }

    private Retrofit getRetrofit(){
        return new Retrofit.Builder()
                .baseUrl("https://developers.zomato.com/api/v2.1/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }

    private ZomatoApi getApi(){
        return  getRetrofit().create(ZomatoApi.class);
    }

    private void getLastLocation(){
        if (ActivityCompat.checkSelfPermission(getContext(),
                Manifest.permission.ACCESS_FINE_LOCATION )!= PackageManager.PERMISSION_GRANTED) {
            requestPermissions();
            return;

        }
    }

    private void requestPermissions(){
        ActivityCompat.requestPermissions(getActivity(),
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                REQUEST_FINE_LOCATION);

    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == REQUEST_FINE_LOCATION) {
            if (grantResults.length <= 0) {
                // If user interaction was interrupted, the permission request is cancelled and you
                // receive empty arrays.
                Log.i(TAG, "User interaction was cancelled.");
            } else if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Permission granted.
                getRestaurants();
            }
        }
    }
    private void getRestaurants(){

        mFusedLocationClient.getLastLocation().addOnSuccessListener(getActivity(), new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                if (location != null) {
                    getApi().getNearbyRestaurants(location.getLatitude(),location.getLongitude(),20,10000,"rating","desc","75be9f9e2239fe637bf9cb1b46979d91")
                            .enqueue(new Callback<ApiResponse>() {
                                @Override
                                public void onResponse(Call<ApiResponse> call, Response<ApiResponse> response) {
                                    List<Restaurant> restaurants=response.body().getRestaurants();
                                    mAdapter = new RestaurantAdapter(context, restaurantsList);
                                    mRecyclerView.setAdapter(mAdapter);
                                    RecyclerView.ItemDecoration itemDecoration = new DividerItemDecoration(context, DividerItemDecoration.VERTICAL);
                                    mRecyclerView.addItemDecoration(itemDecoration);
                                    for (int i = 0; i < restaurants.size(); i++) {
                                        restaurantsList.add(restaurants.get(i).getRestaurant());
                                        mAdapter.notifyItemInserted(i);
                                    }
                                }

                                @Override
                                public void onFailure(Call<ApiResponse> call, Throwable t) {
                                    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
                                    builder.setMessage("Couldn´t find any nearby restaurants");
                                    AlertDialog mDialog = builder.create();
                                    mDialog.show();


                                }
                            });

                }
            }
        }).addOnFailureListener(getActivity(), new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText( getActivity(),"It wasn´t possible to determine your location", Toast.LENGTH_LONG).show();
            }
        });
    }


}

Answer 1

您正在执行两个异步任务，这两个任务都将在未来某个时间点完成（获取位置和进行 Zomato API 调用）。但是你在这里同时做它们。即使位置代码在 API 调用代码之上，它实际上并没有在执行 API 调用之前等待位置。

您需要做的是将 Zomato API 调用移至其自己的方法。然后从 FusedLocationProvider 的onSuccess(Location) 回调方法中调用该方法。这样，您在尝试使用该位置之前等待该位置进入。