Question

我正在开发一个基于位置的聊天应用程序作为最后的任务，但是有一个错误，我无法自己解决。目前，我打算将特定半径内的所有配置文件加载到recyclerview中，并仅向当前用户显示这些配置文件。

Recycler视图运行良好，并显示了Firebase数据库中的每个用户，直到我添加GeoFire查询以将仅出现在2公里范围内的用户限制为。所有用户的经度和纬度都已成功更新到数据库，因此我认为这不是问题的根源。

当我运行该应用程序并崩溃时，我在LogCat中收到此异常：

“ java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'double android.location.Location.getLatitude（）'”

这使我感到困惑，因为我数据库中的当前用户都没有存储经度或纬度的空值。

所以我的主要问题是，如何才能使当前用户周围2公里内的用户填充我的recyclerview，而不会导致应用程序崩溃？

当前源代码：

public class FindChatters extends Fragment {

private RecyclerView mUsersList;
private View mMainView;
private DatabaseReference mUsersDatabase;
private FirebaseUser mCurrentUser;
private LatLng myCurrentLocation;
private String mUserFound;
private static final int RADIUS = 2;
Location mLastLocation;

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

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

    mUsersDatabase = FirebaseDatabase.getInstance().getReference().child("Users");

    mCurrentUser = FirebaseAuth.getInstance().getCurrentUser();

    mUsersList = (RecyclerView) mMainView.findViewById(R.id.users_list);
    mUsersList.setHasFixedSize(true);
    mUsersList.setLayoutManager(new LinearLayoutManager(getContext()));

    return mMainView;

}

//RETRIEVE DATA IN REALTIME
@Override
public void onStart() {
    super.onStart();
    startListening();

}

public void startListening() {
    Query query = FirebaseDatabase.getInstance().getReference().child("Users").limitToLast(50);

    FirebaseRecyclerOptions<Users> options = new FirebaseRecyclerOptions.Builder<Users>().setQuery(query, Users.class).build();

    FirebaseRecyclerAdapter adapter = new FirebaseRecyclerAdapter<Users, UserViewHolder>(options) {
        @Override
        public UserViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            // CREATE NEW INSTANCE OF VIEWHOLDER, USING CUSTOM LAYOUT (R.LAYOUT.MESSAGE)
            View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.users_single_layout, parent, false);

            return new UserViewHolder(view);
        }

        @Override
        protected void onBindViewHolder(final UserViewHolder holder, final int position, final Users model) {

            // // //

            //RETRIEVE CURRENT USERS LAT/LONG TO FIND USERS NEARBY

            String userID = FirebaseAuth.getInstance().getCurrentUser().getUid();
            DatabaseReference myLoc = FirebaseDatabase.getInstance().getReference().child("Geo");
            final GeoFire geoFire = new GeoFire(myLoc);
            geoFire.setLocation(userID, new GeoLocation(mLastLocation.getLatitude(), mLastLocation.getLongitude()));

            myCurrentLocation = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());

            //RETRIEVE USERS ONLY FROM WITHIN A SPECIFIED RADIUS TO THE CURRENT USER
            DatabaseReference findNearby = FirebaseDatabase.getInstance().getReference().child("Geo");
            GeoFire geoFire2 = new GeoFire(findNearby);
            //QUERY ALL NEARBY USERS IN THE DATABASE WITHIN 2KM OF CURRENT USER LAT/LONG
            final GeoQuery geoQuery = geoFire2.queryAtLocation(new GeoLocation(myCurrentLocation.latitude, myCurrentLocation.longitude), RADIUS);

            //QUERY TO RETRIEVE CLOSET USERS
            geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {

                //IF ANY USERS FOUND WITHIN RADIUS - ON KEY ENTERED IS CALLED
                @Override
                public void onKeyEntered(String key, GeoLocation location) {

                    if (geoQuery != null)   {

                        mUserFound = key;

                        //BIND CHAT OBJECT TO CHATHOLDER
                        holder.setName(model.name);
                        holder.setUserStatus(model.status);
                        holder.setUserOnline(model.online);
                        holder.setUserImage(getContext(), model.image);

                        //CLICK ON A USER PROFILE TO ACCESS THEIR INFORMATION OR INITIATE CHAT
                        final String user_id = getRef(position).getKey();

                        //RETRIEVE CURRENT USER ID
                        String current_uid = mCurrentUser.getUid();

                        //PREVENT USER FROM BEING ABLE TO INITIATE A CONVERSATION WITH THEMSELF
                        if (!user_id.equals(current_uid)) {

                            holder.mView.setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {

                                    Intent profileIntent = new Intent(getActivity(), ProfileActivity.class);
                                    profileIntent.putExtra("user_id", user_id);
                                    startActivity(profileIntent);

                                }
                            });

                        } else {

                            holder.setName("You");
                            holder.setUserStatus("Tap someone to say hello!");

                        }


                    } else {

                        //CREATE TEXTVIEW TO INFORM USER THAT NO NEARBY USERS ARE PRESENT

                    }

                }

                @Override
                public void onKeyExited(String key) {

                }

                @Override
                public void onKeyMoved(String key, GeoLocation location) {

                }

                @Override
                public void onGeoQueryReady() {

                }

                @Override
                public void onGeoQueryError(DatabaseError error) {

                }
            });

            // // //

        }

    };
    mUsersList.setAdapter(adapter);
    adapter.startListening();

}

我对编码还是很陌生，因此，我非常感谢您的任何答复或帮助。谢谢！

Android Studio v3.1.3

Answer 1

确保初始化mLastLocation。我可以看到您正在从中检索lat和lng，但从未初始化过

将GeoFire查询加载到RecyclerView时，应用程序崩溃

1 个答案: