使用 FirestoreUI 实现搜索

Question

我一直在尝试使用 firestoreUI 实现搜索，但是当我运行我的代码时 logcat 说：

java.lang.NullPointerException: 尝试在空对象引用上调用虚拟方法 'void com.firebase.ui.firestore.FirestoreRecyclerAdapter.startListening()' 在 com.example.homebarberv1.Search.onStart(Search.java:93)

下面是我的代码：

public class Search extends AppCompatActivity implements FirebaseAuth.AuthStateListener{

private EditText searchField;
private Button searchButton;
private RecyclerView searchRecyclerview;
private FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
private FirestoreRecyclerAdapter<User, UsersViewHolder> adapter;
private String searchText;
static {
    FirebaseFirestore.setLoggingEnabled(true);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getSupportActionBar().hide();
    setContentView(R.layout.activity_search);

    searchField = findViewById(R.id.SearchField);
    searchButton = findViewById(R.id.SearchButton);
    searchRecyclerview = findViewById(R.id.SearchContainer);

    LinearLayoutManager manager = new LinearLayoutManager(this);
    manager.setReverseLayout(true);
    manager.setStackFromEnd(true);

    searchRecyclerview .setHasFixedSize(true);
    searchRecyclerview .setLayoutManager(manager);

    BottomNavigationView bottomNavigationView = findViewById(R.id.bottomNavigationView);
    bottomNavigationView.setSelectedItemId(R.id.search);

    bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()){
                case R.id.search:
                    return true;
                case R.id.appointment:
                    startActivity(new Intent(getApplicationContext(),HomePage.class));
                    overridePendingTransition(0,0);
                    return true;
                case R.id.profile:
                    startActivity(new Intent(getApplicationContext(),Profile.class));
                    overridePendingTransition(0,0);
                    return true;
            }
            return false;
        }
    });

    searchButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            searchText = searchField.getText().toString();
            firebaseUserSearch(searchText);
        }
    });
}

@Override
public void onStart() {
    super.onStart();
    if (isSignedIn()) {
        adapter.startListening();
    }
    firebaseAuth.addAuthStateListener(this);
}

@Override
protected void onStop() {
    super.onStop();
    adapter.stopListening();
    FirebaseAuth.getInstance().removeAuthStateListener(this);
}

@Override
public void onAuthStateChanged(@NonNull FirebaseAuth auth) {
    if (isSignedIn()) {
        adapter.startListening();
    } else {
       Toast.makeText(Search.this,"user are not signed in",Toast.LENGTH_LONG);
    }
}

private boolean isSignedIn() {
    return FirebaseAuth.getInstance().getCurrentUser() != null;
}


@NonNull
private void firebaseUserSearch(String searchText){

    CollectionReference sCollection =
            FirebaseFirestore.getInstance().collection("Barbers");
    Query sQuery = sCollection.startAt(searchText).endAt(searchText + "\uf8ff");

    FirestoreRecyclerOptions<User> options =
            new FirestoreRecyclerOptions.Builder<User>()
                    .setQuery(sQuery, User.class)
                    .setLifecycleOwner(this)
                    .build();

    adapter = new FirestoreRecyclerAdapter<User, UsersViewHolder>(options) {

        @NonNull
        @Override
        public UsersViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.searchlist, parent, false);
            return new UsersViewHolder(view);
        }

        @Override
        protected void onBindViewHolder(@NonNull UsersViewHolder holder, int position, @NonNull User model) {
            holder.setName(model.getShopname());
            holder.setPic(model.getPiclink());
            holder.setAddress(model.getAddress() + ", " + model.getPostcode().toString() + ", " + model.getCity());
        }
    };

    searchRecyclerview.setAdapter(adapter);
}

public class UsersViewHolder extends RecyclerView.ViewHolder {
    private View mView;

    public UsersViewHolder(View itemView) {
        super(itemView);
        mView = itemView;
    }

    public void setName(String name){
        TextView userNameView = (TextView) mView.findViewById(R.id.shopNameS);
        userNameView.setText(name);
    }
    public void setPic(String link){
        ImageView imageView = (ImageView)mView.findViewById(R.id.imageS);
        Picasso.get().load(link).into(imageView);
    }
    public void setAddress(String address){
        TextView addressView = (TextView) mView.findViewById(R.id.shopAddressS);
        addressView.setText(address);
    }

}

}

错误指的是这一行：

adapter.startListening();

我还是Android的新手，所以我不太明白我在这里做错了什么，非常感谢帮助

Answer 1

在调用 adapter.startListening 之前，您需要确保 adapter 已被赋值。

这意味着在 onStart 中您需要确保适配器存在：

@Override
public void onStart() {
    super.onStart();
    if (isSignedIn() && adapter != null) {
        adapter.startListening();
    }
    firebaseAuth.addAuthStateListener(this);
}

然后在创建适配器并且用户登录时也开始监听适配器。因此：

adapter = new FirestoreRecyclerAdapter<User, UsersViewHolder>(options) {
    ...
});
if (isSignedIn()) {
    adapter.startListening();
}

使用 FirestoreUI 实现搜索

implementing search with FirestoreUI

java

android

firebaseui

google-cloud-firestore