在Fragment-Android中使用FirestoreRecyclerAdapter时获取NullPointerException

问题描述 投票：0回答：1

我无法在FirestoreRecylerView中看到我的数据。将startListening添加到适配器时，我得到了NPE。我没有使用onCreate方法。我读了一个类似问题的答案，其中建议使用onCreate。但是，我认为我不需要onCreate。有什么办法可以解决这个问题？

这是我的片段代码，我想在其中查看回收站：

package com.example.XX;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.recyclerview.widget.RecyclerView;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import com.firebase.ui.firestore.FirestoreRecyclerOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.android.gms.tasks.Tasks;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.firestore.DocumentReference;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.Query;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;

import java.util.List;


public class MainQueryFragment extends Fragment {

    RecyclerView recyclerView;
    ProfileRecyclerAdapter ProfileRecyclerAdapter;
    TextView yourSector;
    TextView yourPincode;
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    String tuserID = FirebaseAuth.getInstance().getCurrentUser().getUid();
    String customerPincode;
    String customerSector;
    String sectorText;
    String pincodeText;
    String[] testArray;
    String name;
    String pincode;
    String address;
    String mobileNumber;
    String sector;
    String avgDeliveryTime;
    String avgDeliveryTimeUrg;

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

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

        return view;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        yourSector = view.findViewById(R.id.Sector_tv);
        yourPincode = view.findViewById(R.id.Pincode_tv);
        recyclerView = view.findViewById(R.id.recylerView_Profile);

        DocumentReference docRef = db.collection("customerUsers").document(tuserID);
        docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                    DocumentSnapshot document = task.getResult();
                    if (document.exists()) {
                        customerPincode = document.getString("pincode");
                        customerSector = document.getString("sector");
                        sectorText = "Sector : " + customerSector;
                        pincodeText = "Pincode : " + customerPincode;
                        yourSector.setText(sectorText);
                        yourPincode.setText(pincodeText);
                   } else {
                        Log.d("docref", "No such document");
                    }
                } else {
                    Log.d("docref", "get failed with ", task.getException());
                }
            }
        });


        Button button = view.findViewById(R.id.startQuery_button);
        if (getArguments() != null) {
            MainQueryFragmentArgs args = MainQueryFragmentArgs.fromBundle(getArguments());
            testArray = args.getArrayCheckboxData();

        }


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Query query = FirebaseFirestore.getInstance()
                        .collection("tUsers")
                        .whereEqualTo("pincode", customerPincode)
                        .whereEqualTo("sector", customerSector)
                        .whereEqualTo(testArray[0], true)
                        .whereEqualTo(testArray[1], true)
                        .whereEqualTo(testArray[2], true)
                        .whereEqualTo(testArray[3], true);


                FirestoreRecyclerOptions<Profile> options = new FirestoreRecyclerOptions.Builder<Profile>()
                        .setQuery(query,Profile.class)
                        .build();

                ProfileRecyclerAdapter = new ProfileRecyclerAdapter(options);
                recyclerView.setAdapter(ProfileRecyclerAdapter);
           }
        });
    }

    @Override
    public void onStart() {
        super.onStart();
        ProfileRecyclerAdapter.startListening();
    }

    @Override
    public void onStop() {
        super.onStop();
        ProfileRecyclerAdapter.stopListening();
    }
}

这是我的适配器类：

package com.example.XX;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.firebase.ui.firestore.FirestoreRecyclerAdapter;
import com.firebase.ui.firestore.FirestoreRecyclerOptions;

public class ProfileRecyclerAdapter extends FirestoreRecyclerAdapter<Profile,ProfileRecyclerAdapter.ProfileViewHolder> {


      public ProfileRecyclerAdapter(@NonNull FirestoreRecyclerOptions<Profile> options) {
        super(options);
    }


    @Override
    protected void onBindViewHolder(@NonNull ProfileViewHolder holder, int position, @NonNull Profile profile) {
        holder.Name_textView.setText(profile.getName());
        holder.Sector_textView.setText(profile.getSector());
        holder.Pincode_textView.setText(profile.getPincode());

    }

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

    }


    class ProfileViewHolder extends RecyclerView.ViewHolder{

        TextView Name_textView;
        TextView Sector_textView;
        TextView Pincode_textView;

        public ProfileViewHolder(@NonNull View itemView) {
            super(itemView);

            Name_textView=itemView.findViewById(R.id.Name_textView);
            Sector_textView=itemView.findViewById(R.id.Sector_textView);
            Pincode_textView=itemView.findViewById(R.id.Pincode_textView);
        }
    }
}

我的日志：

2020-06-14 12:17:53.043 32238-32238/com.example.XX E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.XX, PID: 32238
    java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.XX.ProfileRecyclerAdapter.startListening()' on a null object reference
        at com.example.XX.MainQueryFragment.onStart(MainQueryFragment.java:172)
        at androidx.fragment.app.Fragment.performStart(Fragment.java:2730)
        at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:365)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1194)
        at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
        at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7710)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

编辑：这是我的最新尝试，但仍未显示任何内容。我仍然得到E/RecyclerView: No adapter attached; skipping layout，我相信我已经在onCreateView中添加了空适配器。 ：

public class MainQueryFragment extends Fragment {

    RecyclerView recyclerView;
    ProfileRecyclerAdapter ProfileRecyclerAdapter;
    TextView yourSector;
    TextView yourPincode;
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    String tuserID = FirebaseAuth.getInstance().getCurrentUser().getUid();
    String customerPincode;
    String customerSector;
    String sectorText;
    String pincodeText;
    String[] testArray;
    String name;
    String pincode;
    String address;
    String mobileNumber;
    String sector;
    String avgDeliveryTime;
    String avgDeliveryTimeUrg;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_main_query, container, false);
        recyclerView =view.findViewById(R.id.recyclerView_Profile);

        recyclerView.setAdapter(ProfileRecyclerAdapter);
        return view;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        yourSector = view.findViewById(R.id.Sector_tv);
        yourPincode = view.findViewById(R.id.Pincode_tv);
        recyclerView = view.findViewById(R.id.recylerView_Profile);

        DocumentReference docRef = db.collection("customerUsers").document(tuserID);
        docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                    DocumentSnapshot document = task.getResult();
                    if (document.exists()) {
                        customerPincode = document.getString("pincode");
                        customerSector = document.getString("sector");
                        sectorText = "Sector : " + customerSector;
                        pincodeText = "Pincode : " + customerPincode;
                        yourSector.setText(sectorText);
                        yourPincode.setText(pincodeText);
                   } else {
                        Log.d("docref", "No such document");
                    }
                } else {
                    Log.d("docref", "get failed with ", task.getException());
                }
            }
        });


        Button button = view.findViewById(R.id.startQuery_button);
        if (getArguments() != null) {
            MainQueryFragmentArgs args = MainQueryFragmentArgs.fromBundle(getArguments());
            testArray = args.getArrayCheckboxData();

        }


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Query query = FirebaseFirestore.getInstance()
                        .collection("tUsers")
                        .whereEqualTo("pincode", customerPincode)
                        .whereEqualTo("sector", customerSector)
                        .whereEqualTo(testArray[0], true)
                        .whereEqualTo(testArray[1], true)
                        .whereEqualTo(testArray[2], true)
                        .whereEqualTo(testArray[3], true);


                FirestoreRecyclerOptions<Profile> options = new FirestoreRecyclerOptions.Builder<Profile>()
                        .setQuery(query,Profile.class)
                        .build();

                ProfileRecyclerAdapter = new ProfileRecyclerAdapter(options);
                recyclerView.setAdapter(ProfileRecyclerAdapter);
                ProfileRecyclerAdapter.startListening();
           }
        });
    }

}

如果在onCreate中添加recyclerView.setAdapter(ProfileRecyclerAdapter);，我会得到NPE！

java android firebase google-cloud-firestore nullpointerexception
1个回答
0
投票

您正在onClickListener内部初始化适配器，因此，当您运行该应用程序并调用所有生命周期时，由于ProfileRecyclerAdapter ProfileRecyclerAdapter;等于null，因此将出现此异常。您需要将startListening()移到clickListener内：


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Query query = FirebaseFirestore.getInstance()
                        .collection("tUsers")
                        .whereEqualTo("pincode", customerPincode)
                        .whereEqualTo("sector", customerSector)
                        .whereEqualTo(testArray[0], true)
                        .whereEqualTo(testArray[1], true)
                        .whereEqualTo(testArray[2], true)
                        .whereEqualTo(testArray[3], true);


                FirestoreRecyclerOptions<Profile> options = new FirestoreRecyclerOptions.Builder<Profile>()
                        .setQuery(query,Profile.class)
                        .build();

                ProfileRecyclerAdapter = new ProfileRecyclerAdapter(options);
                recyclerView.setAdapter(ProfileRecyclerAdapter);
                ProfileRecyclerAdapter.startListening();
           }
        });
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