java - 当我尝试从 Firestore 获取数据并显示在 ListView fragment 中时，我的应用程序崩溃了

Question

当我尝试从 firestore 访问数据并将其显示在 ListView fragment 类中时，我的应用程序崩溃了。任何帮助都会对我有益

availablestudent_fragment.java(主 fragment 类)

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.google.firebase.firestore.DocumentChange;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.EventListener;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.FirebaseFirestoreException;
import com.google.firebase.firestore.QuerySnapshot;
import com.google.firebase.firestore.auth.User;

import java.util.ArrayList;
import java.util.List;

public class availablestudent_fragment extends Fragment {

    private static final String TAG ="FireLog" ;
    private RecyclerView nmainlist;
    private FirebaseFirestore mfirestore;
    private List<Users> usersList;
    private UserListAdapter userListAdapter;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v=inflater.inflate(R.layout.fragment_availablestudents,null);

        nmainlist=(RecyclerView)v.findViewById(R.id.main_list);
        nmainlist.setHasFixedSize(true);
        nmainlist.setLayoutManager(new LinearLayoutManager(getContext()));
        nmainlist.setAdapter(userListAdapter);
        mfirestore=FirebaseFirestore.getInstance();

      usersList=new ArrayList<>();
      userListAdapter=new UserListAdapter(usersList);


        mfirestore.collection("users").addSnapshotListener(new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@javax.annotation.Nullable QuerySnapshot queryDocumentSnapshots, @javax.annotation.Nullable FirebaseFirestoreException e) {
                if (e != null) {
                    Log.d(TAG, "Error" + e.getMessage());
                }

                for (DocumentChange doc : queryDocumentSnapshots.getDocumentChanges()) {


                    if (doc.getType() == DocumentChange.Type.ADDED) {
                        Users users = doc.getDocument().toObject(Users.class);
                        usersList.add(users);
                        userListAdapter.notifyDataSetChanged();
                    }
                }

            }
        });
        return v;
    }
}

users.java(模型类)

    package com.kiit.projectmanager;

public class Users {

    String Student_Name,Roll_Number;

    public  Users(){

    }

    public Users(String student_Name, String roll_Number) {
        this.Student_Name = student_Name;
        this.Roll_Number = roll_Number;
    }

    public String getStudent_Name() {
        return Student_Name;
    }

    public void setStudent_Name(String student_Name) {
      this.Student_Name = student_Name;
    }

    public String getRoll_Number() {
        return Roll_Number;
    }

    public void setRoll_Number(String roll_Number) {
        this.Roll_Number = roll_Number;
    }


}

UsersListAdapter.java

import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.google.firebase.firestore.auth.User;

import org.w3c.dom.Text;

import java.util.List;

public class UserListAdapter extends RecyclerView.Adapter<UserListAdapter.ViewHolder> {
   public List<Users> usersList;

   public  UserListAdapter(List<Users> usersList){
       this.usersList=usersList;
   }


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

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {

       holder.StudentName.setText(usersList.get(position).getStudent_Name());
        holder.RollNumber.setText(usersList.get(position).getRoll_Number());

    }

    @Override
    public int getItemCount() {
        return usersList.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        View mview;
        public TextView StudentName;
        public TextView RollNumber;


        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            mview=itemView;

            StudentName=(TextView)mview.findViewById(R.id.name);
            RollNumber=(TextView)mview.findViewById(R.id.rollnumber);
        }
    }
}

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="13dp"
    android:padding="13dp">

    <TextView
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="@font/mirza_semibold"

        android:text="NAME"
        android:textColor="@color/common_google_signin_btn_text_dark_focused"
        android:textSize="18dp" />

    <TextView
        android:id="@+id/rollnumber"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="@font/fjalla_one"
        android:text="ROLLNUMBER"
        android:textColor="@color/common_google_signin_btn_text_dark_focused"
        android:textSize="14dp" />

</LinearLayout>

Fragment_availablestudents.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/main_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>

</LinearLayout>

logcat_Error(当我尝试单击我的 fragment 时，我的应用程序崩溃了)

    03-29 19:28:58.838 18481-18677/com.kiit.projectmanager I/OpenGLRenderer: Initialized EGL, version 1.4
03-29 19:28:58.876 18481-18481/com.kiit.projectmanager W/art: Before Android 4.1, method int android.support.v7.widget.DropDownListView.lookForSelectablePosition(int, boolean) would have incorrectly overridden the package-private method in android.widget.ListView
03-29 19:28:58.956 18481-18677/com.kiit.projectmanager E/HAL: hw_get_module_by_class: module name gralloc
03-29 19:28:58.956 18481-18677/com.kiit.projectmanager E/HAL: hw_get_module_by_class: module name gralloc
03-29 19:28:59.054 18481-18638/com.kiit.projectmanager D/FA: Connected to remote service
03-29 19:28:59.900 18481-18481/com.kiit.projectmanager I/Timeline: Timeline: Activity_launch_request time:50369167
03-29 19:28:59.920 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): user_engagement(_e), Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=1162, firebase_screen_class(_sc)=MainActivity, firebase_screen_id(_si)=9078248192392117239}]
03-29 19:29:00.229 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): screen_view(_vs), Bundle[{firebase_event_origin(_o)=auto, firebase_previous_class(_pc)=MainActivity, firebase_previous_id(_pi)=9078248192392117239, firebase_screen_class(_sc)=login_activity, firebase_screen_id(_si)=9078248192392117240}]
03-29 19:29:02.730 18481-18481/com.kiit.projectmanager I/Choreographer: Skipped 146 frames!  The application may be doing too much work on its main thread.
03-29 19:29:04.698 18481-18481/com.kiit.projectmanager I/Choreographer: Skipped 117 frames!  The application may be doing too much work on its main thread.
03-29 19:29:04.705 18481-18481/com.kiit.projectmanager I/Timeline: Timeline: Activity_launch_request time:50373972
03-29 19:29:04.724 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): user_engagement(_e), Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=4492, firebase_screen_class(_sc)=login_activity, firebase_screen_id(_si)=9078248192392117240}]
03-29 19:29:04.763 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): screen_view(_vs), Bundle[{firebase_event_origin(_o)=auto, firebase_previous_class(_pc)=login_activity, firebase_previous_id(_pi)=9078248192392117240, firebase_screen_class(_sc)=student_login, firebase_screen_id(_si)=9078248192392117241}]
03-29 19:29:07.105 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:07.105 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:10.300 18481-18638/com.kiit.projectmanager D/FA: Setting user property (FE): _sid, 1553867950
03-29 19:29:10.341 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): session_start(_s), Bundle[{firebase_event_origin(_o)=auto, firebase_screen_class(_sc)=student_login, firebase_screen_id(_si)=9078248192392117241, session_id(_sid)=1553867950}]
03-29 19:29:10.376 18481-18638/com.kiit.projectmanager D/FA: Connected to remote service
03-29 19:29:11.005 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:11.005 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:11.666 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:11.666 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:15.494 18481-18481/com.kiit.projectmanager W/IInputConnectionWrapper: getExtractedText on inactive InputConnection
03-29 19:29:15.497 18481-18481/com.kiit.projectmanager W/IInputConnectionWrapper: getTextBeforeCursor on inactive InputConnection
03-29 19:29:15.499 18481-18481/com.kiit.projectmanager W/IInputConnectionWrapper: setComposingRegion on inactive InputConnection
03-29 19:29:19.178 18481-18481/com.kiit.projectmanager W/BiChannelGoogleApi: [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzal@8cbf476
03-29 19:29:20.161 18481-18481/com.kiit.projectmanager I/Toast: Show toast from OpPackageName:com.kiit.projectmanager, PackageName:com.kiit.projectmanager
03-29 19:29:24.288 18481-18481/com.kiit.projectmanager W/BiChannelGoogleApi: [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzal@8cbf476
03-29 19:29:24.781 18481-18481/com.kiit.projectmanager I/Toast: Show toast from OpPackageName:com.kiit.projectmanager, PackageName:com.kiit.projectmanager
03-29 19:29:29.533 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:29.533 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:30.249 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:30.250 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:30.320 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:30.320 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:32.446 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:32.446 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:32.769 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:32.769 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:36.362 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:36.362 18481-18481/com.kiit.projectmanager E/SpannableStringBuilder: SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
03-29 19:29:42.405 18481-18481/com.kiit.projectmanager W/BiChannelGoogleApi: [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzal@8cbf476
03-29 19:29:44.406 18481-18583/com.kiit.projectmanager D/FirebaseAuth: Notifying id token listeners about user ( yBhPtTpYDdQgviffTlUvhLwAOPn1 ).
03-29 19:29:44.420 18481-18481/com.kiit.projectmanager D/FirebaseApp: Notifying auth state listeners.
03-29 19:29:44.420 18481-18481/com.kiit.projectmanager D/FirebaseApp: Notified 0 auth state listeners.
03-29 19:29:44.437 18481-18481/com.kiit.projectmanager I/Timeline: Timeline: Activity_launch_request time:50413704
03-29 19:29:44.475 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): user_engagement(_e), Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=39712, firebase_screen_class(_sc)=student_login, firebase_screen_id(_si)=9078248192392117241}]
03-29 19:29:44.646 18481-19899/com.kiit.projectmanager W/DynamiteModule: Local module descriptor class for providerinstaller not found.
03-29 19:29:44.652 18481-18638/com.kiit.projectmanager D/FA: Logging event (FE): screen_view(_vs), Bundle[{firebase_event_origin(_o)=auto, firebase_previous_class(_pc)=student_login, firebase_previous_id(_pi)=9078248192392117241, firebase_screen_class(_sc)=student_activity, firebase_screen_id(_si)=9078248192392117242}]
03-29 19:29:44.655 18481-19899/com.kiit.projectmanager I/DynamiteModule: Considering local module providerinstaller:0 and remote module providerinstaller:0
03-29 19:29:44.655 18481-19899/com.kiit.projectmanager W/ProviderInstaller: Failed to load providerinstaller module: No acceptable module found. Local version is 0 and remote version is 0.
03-29 19:29:44.656 18481-19899/com.kiit.projectmanager W/ResourceType: No package identifier when getting name for resource number 0x00000000
03-29 19:29:44.817 18481-18638/com.kiit.projectmanager D/FA: Connected to remote service
03-29 19:29:44.884 18481-19899/com.kiit.projectmanager I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.android.gms.org.conscrypt.Java7ExtendedSSLSession>
03-29 19:29:44.885 18481-19899/com.kiit.projectmanager I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.android.gms.org.conscrypt.Java7ExtendedSSLSession>
03-29 19:29:44.888 18481-19899/com.kiit.projectmanager I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.android.gms.org.conscrypt.Java8ExtendedSSLSession>
03-29 19:29:44.889 18481-19899/com.kiit.projectmanager I/art: Rejecting re-init on previously-failed class java.lang.Class<com.google.android.gms.org.conscrypt.Java8ExtendedSSLSession>
03-29 19:29:44.946 18481-19899/com.kiit.projectmanager I/ProviderInstaller: Installed default security provider GmsCore_OpenSSL
03-29 19:29:45.890 18481-18481/com.kiit.projectmanager W/PathParser: Points are too far apart 4.000000596046461
03-29 19:29:48.115 18481-18481/com.kiit.projectmanager E/RecyclerView: No adapter attached; skipping layout
03-29 19:29:48.134 18481-18481/com.kiit.projectmanager W/PathParser: Points are too far apart 4.000000596046461
03-29 19:29:48.467 18481-18481/com.kiit.projectmanager D/AndroidRuntime: Shutting down VM
03-29 19:29:48.468 18481-18481/com.kiit.projectmanager E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.kiit.projectmanager, PID: 18481
    java.lang.RuntimeException: Found two getters or fields with conflicting case sensitivity for property: roll_number
        at com.google.firebase.firestore.util.CustomClassMapper$BeanMapper.addProperty(com.google.firebase:firebase-firestore@@18.1.0:670)
        at com.google.firebase.firestore.util.CustomClassMapper$BeanMapper.<init>(com.google.firebase:firebase-firestore@@18.1.0:586)
        at com.google.firebase.firestore.util.CustomClassMapper.loadOrCreateBeanMapperForClass(com.google.firebase:firebase-firestore@@18.1.0:348)
        at com.google.firebase.firestore.util.CustomClassMapper.convertBean(com.google.firebase:firebase-firestore@@18.1.0:502)
        at com.google.firebase.firestore.util.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-firestore@@18.1.0:243)
        at com.google.firebase.firestore.util.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-firestore@@18.1.0:97)
        at com.google.firebase.firestore.DocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:203)
        at com.google.firebase.firestore.QueryDocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:121)
        at com.google.firebase.firestore.DocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:183)
        at com.google.firebase.firestore.QueryDocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:101)
        at com.kiit.projectmanager.availablestudent_fragment$1.onEvent(availablestudent_fragment.java:59)
        at com.kiit.projectmanager.availablestudent_fragment$1.onEvent(availablestudent_fragment.java:48)
        at com.google.firebase.firestore.Query.lambda$addSnapshotListenerInternal$2(com.google.firebase:firebase-firestore@@18.1.0:891)
        at com.google.firebase.firestore.Query$$Lambda$3.onEvent(com.google.firebase:firebase-firestore@@18.1.0)
        at com.google.firebase.firestore.util.ExecutorEventListener.lambda$onEvent$0(com.google.firebase:firebase-firestore@@18.1.0:42)
        at com.google.firebase.firestore.util.ExecutorEventListener$$Lambda$1.run(com.google.firebase:firebase-firestore@@18.1.0)
        at android.os.Handler.handleCallback(Handler.java:742)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:157)
        at android.app.ActivityThread.main(ActivityThread.java:5603)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:774)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)
03-29 19:29:58.480 18481-19899/com.kiit.projectmanager W/Firestore: (18.1.0) [OnlineStateTracker]: Could not reach Cloud Firestore backend. Backend didn't respond within 10 seconds

    This typically indicates that your device does not have a healthy Internet connection at the moment. The client will operate in offline mode until it is able to successfully connect to the backend.

从单元格检索错误以使其更清晰

   java.lang.RuntimeException: Found two getters or fields with conflicting case sensitivity for property: roll_number
    at com.google.firebase.firestore.util.CustomClassMapper$BeanMapper.addProperty(com.google.firebase:firebase-firestore@@18.1.0:670)
    at com.google.firebase.firestore.util.CustomClassMapper$BeanMapper.<init>(com.google.firebase:firebase-firestore@@18.1.0:586)
    at com.google.firebase.firestore.util.CustomClassMapper.loadOrCreateBeanMapperForClass(com.google.firebase:firebase-firestore@@18.1.0:348)
    at com.google.firebase.firestore.util.CustomClassMapper.convertBean(com.google.firebase:firebase-firestore@@18.1.0:502)
    at com.google.firebase.firestore.util.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-firestore@@18.1.0:243)
    at com.google.firebase.firestore.util.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-firestore@@18.1.0:97)
    at com.google.firebase.firestore.DocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:203)
    at com.google.firebase.firestore.QueryDocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:121)
    at com.google.firebase.firestore.DocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:183)
    at com.google.firebase.firestore.QueryDocumentSnapshot.toObject(com.google.firebase:firebase-firestore@@18.1.0:101)
    at com.kiit.projectmanager.availablestudent_fragment$1.onEvent(availablestudent_fragment.java:59)
    at com.kiit.projectmanager.availablestudent_fragment$1.onEvent(availablestudent_fragment.java:48)
    at com.google.firebase.firestore.Query.lambda$addSnapshotListenerInternal$2(com.google.firebase:firebase-firestore@@18.1.0:891)
    at com.google.firebase.firestore.Query$$Lambda$3.onEvent(com.google.firebase:firebase-firestore@@18.1.0)
    at com.google.firebase.firestore.util.ExecutorEventListener.lambda$onEvent$0(com.google.firebase:firebase-firestore@@18.1.0:42)
    at com.google.firebase.firestore.util.ExecutorEventListener$$Lambda$1.run(com.google.firebase:firebase-firestore@@18.1.0)
    at android.os.Handler.handleCallback(Handler.java:742)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:157)
    at android.app.ActivityThread.main(ActivityThread.java:5603)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:774)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)

Answer 1

要解决此问题，您需要根据 Java Naming Conventions 修复 Users 类中字段和方法的大小写。 。所以你的模型类应该是这样的:

public class Users {
    String studentName, rollNumber;

    public Users(){}

    public Users(String studentName, String rollNumber) {
        this.studentName = studentName;
        this.rollNumber = rollNumber;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public String getRollNumber() {
        return rollNumber;
    }

    public void setRollNumber(String rollNumber) {
        this.rollNumber = rollNumber;
    }
}

删除旧数据，添加新数据，一切都会正常工作。