recyclerview未显示firebase firestore和Crash应用程序中的数据

lrl1mhuk  于 2021-08-25  发布在  Java
关注(0)|答案(1)|浏览(373)

试图让我的recyclerview显示firestore中的数据，但它使我的应用程序崩溃，我不知道为什么。我看了很多教程，但都没用，我一步一步地跟着教程，不太清楚为什么教程可以用，而我的却不行。任何帮助都将不胜感激。
建立梯度

  1. plugins {
  2.     id 'com.android.application'
  3.     id 'com.google.gms.google-services'
  4. }
  6. android {
  7.     compileSdkVersion 30
  8.     buildToolsVersion "30.0.3"
  10.     defaultConfig {
  11.         applicationId "com.example.orbital"
  12.         minSdkVersion 21
  13.         targetSdkVersion 30
  14.         versionCode 1
  15.         versionName "1.0"
  17.         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
  18.     }
  20.     buildTypes {
  21.         release {
  22.             minifyEnabled false
  23.             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
  24.         }
  25.     }
  26.     compileOptions {
  27.         sourceCompatibility JavaVersion.VERSION_1_8
  28.         targetCompatibility JavaVersion.VERSION_1_8
  29.     }
  30. }
  32. dependencies {
  33.     implementation 'com.google.android.material:material:1.3.0'
  34.     implementation 'androidx.appcompat:appcompat:1.3.0'
  35.     implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
  36.     implementation 'androidx.cardview:cardview:1.0.0'
  37.     implementation 'com.google.firebase:firebase-auth:21.0.1'
  38.     implementation 'com.google.firebase:firebase-firestore:23.0.1'
  39.     implementation 'com.google.firebase:firebase-database:20.0.0'
  40.     implementation 'com.google.firebase:firebase-storage:20.0.0'
  41.     implementation 'com.airbnb.android:lottie:3.4.1'
  42.     implementation 'com.firebaseui:firebase-ui-firestore:7.2.0'
  43.     implementation 'androidx.recyclerview:recyclerview:1.0.0'
  45.     testImplementation 'junit:junit:4.+'
  46.     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
  47.     androidTestImplementation 'androidx.test.ext:junit:1.1.2'
  48.     androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
  50. }

从firestore检索数据的聊天片段

  1. package com.example.orbital;
  3. import android.graphics.Color;
  4. import android.os.Bundle;
  5. import android.view.LayoutInflater;
  6. import android.view.View;
  7. import android.view.ViewGroup;
  8. import android.widget.TextView;
  9. import android.widget.Toast;
  11. import androidx.annotation.NonNull;
  12. import androidx.annotation.Nullable;
  13. import androidx.fragment.app.Fragment;
  14. import androidx.recyclerview.widget.LinearLayoutManager;
  15. import androidx.recyclerview.widget.RecyclerView;
  17. import com.firebase.ui.firestore.FirestoreRecyclerAdapter;
  18. import com.firebase.ui.firestore.FirestoreRecyclerOptions;
  19. import com.google.firebase.auth.FirebaseAuth;
  20. import com.google.firebase.firestore.FirebaseFirestore;
  21. import com.google.firebase.firestore.FirebaseFirestoreException;
  22. import com.google.firebase.firestore.Query;
  24. public class chatFragment extends Fragment {
  26.     private FirebaseFirestore firebaseFirestore;
  27.     LinearLayoutManager linearLayoutManager;
  28.     private FirebaseAuth firebaseAuth;
  30.     FirestoreRecyclerAdapter<UserModel, NoteViewHolder> chatAdapter;
  31.     RecyclerView mRecyclerView;
  33.     @Nullable
  34.     @Override
  35.     public View onCreateView(@NonNull LayoutInflater inflater, @Nullable  ViewGroup container, @Nullable  Bundle savedInstanceState) {
  36.         View v = inflater.inflate(R.layout.chatfragment,container,false);
  38.         firebaseAuth = FirebaseAuth.getInstance();
  39.         firebaseFirestore = FirebaseFirestore.getInstance();
  40.         mRecyclerView = v.findViewById(R.id.recyclerView);
  42.         Query query = firebaseFirestore.collection("Users");
  43.         FirestoreRecyclerOptions<UserModel> allusername = new FirestoreRecyclerOptions.Builder<UserModel>()
  44.                 .setQuery(query,UserModel.class)
  45.                 .build();
  47.         chatAdapter = new FirestoreRecyclerAdapter<UserModel, NoteViewHolder>(allusername) {
  48.             @Override
  49.             public void onError(FirebaseFirestoreException e) {
  50.                 // Called when there is an error getting a query snapshot. You may want to update
  51.                 // your UI to display an error message to the user.
  52.                 // ...
  54.             }
  56.             @Override
  57.             protected void onBindViewHolder(@NonNull NoteViewHolder noteViewHolder, int i, @NonNull UserModel userModel) {
  59.                 noteViewHolder.particularusername.setText(userModel.getName());
  60.                 //fetch image
  61.                 /*if(UserModel.getStatus().equals("Online"))
  62.                 {
  63.                     holder.statusofuser.setText(model.getStatus());
  64.                     holder.statusofuser.setTextColor(Color.GREEN);
  65.                 }
  66.                 else
  67.                 {
  68.                     holder.statusofuser.setText(model.getStatus());
  69.                 }*/
  71.                 noteViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
  72.                     @Override
  73.                     public void onClick(View v) {
  74.                         Toast.makeText(getActivity(),"Chat Clicked",Toast.LENGTH_SHORT).show();
  75.                     }
  76.                 });
  78.             }
  80.             @NonNull
  81.             @Override
  82.             public NoteViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
  84.                 View view=LayoutInflater.from(parent.getContext()).inflate(R.layout.chatview_layout,parent,false);
  85.                 return new NoteViewHolder(view);
  86.             }
  87.         };
  89.         //mRecyclerView.setHasFixedSize(true);
  90.         linearLayoutManager=new LinearLayoutManager(getContext());
  91.         linearLayoutManager.setOrientation(RecyclerView.VERTICAL);
  92.         mRecyclerView.setLayoutManager(linearLayoutManager);
  93.         mRecyclerView.setAdapter(chatAdapter);
  95.        return v;
  97.     }
  99.     public class NoteViewHolder extends RecyclerView.ViewHolder
  100.     {
  101.         //suppose to add on image
  102.         private TextView particularusername;
  103.         //private TextView statusofuser;
  105.         public NoteViewHolder(@NonNull View itemView) {
  106.             super(itemView);
  107.             particularusername=itemView.findViewById(R.id.nameofuser);
  108.             //statusofuser=itemView.findViewById(R.id.statusofuser);
  110.         }
  112.     }
  114.     @Override
  115.     public void onStart() {
  116.         super.onStart();
  117.         chatAdapter.startListening();
  118.     }
  120.     @Override
  121.     public void onStop() {
  122.         super.onStop();
  124.         chatAdapter.stopListening();
  125.     }
  127. }

chatviewlayout（xml）

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <RelativeLayout
  3.     xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
  4.     android:layout_height="match_parent"
  5.     android:background="@color/white">
  7.     <androidx.recyclerview.widget.RecyclerView
  8.         android:layout_width="match_parent"
  9.         android:layout_height="match_parent"
  10.         android:id="@+id/recyclerview">
  12.     </androidx.recyclerview.widget.RecyclerView>
  14. </RelativeLayout>

聊天片段（xml）

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     android:layout_width="match_parent"
  4.     android:layout_height="90dp"
  5.     xmlns:app="http://schemas.android.com/apk/res-auto"
  6.     android:background="@color/smokyWhite">
  8.     <RelativeLayout
  9.         android:layout_width="match_parent"
  10.         android:layout_height="match_parent"
  11.         android:paddingLeft="10dp"
  12.         android:paddingRight="10dp"
  13.         android:paddingTop="10dp"
  14.         android:paddingBottom="-5dp">
  16.         <TextView
  17.             android:layout_width="wrap_content"
  18.             android:layout_height="wrap_content"
  19.             android:text="Name Display Here"
  20.             android:layout_toRightOf="@id/cardviewofuser"
  21.             android:layout_marginTop="15dp"
  22.             android:layout_marginLeft="15dp"
  23.             android:textSize="20sp"
  24.             android:id="@+id/nameofuser"
  25.             android:textStyle="bold"
  26.             android:textColor="#0b0b0b">
  28.         </TextView>
  30.         <TextView
  31.             android:layout_width="wrap_content"
  32.             android:layout_height="wrap_content"
  33.             android:text="Display Status here"
  34.             android:textSize="12sp"
  35.             android:layout_marginLeft="15dp"
  36.             android:layout_marginTop="3dp"
  37.             android:layout_toRightOf="@id/cardviewofuser"
  38.             android:id="@+id/statusofuser"
  39.             android:layout_below="@id/nameofuser"
  40.             android:textColor="#6a6a6a">
  42.         </TextView>
  44.         <androidx.cardview.widget.CardView
  45.             android:layout_width="55dp"
  46.             android:layout_height="55dp"
  47.             android:layout_marginBottom="20dp"
  48.             android:layout_alignParentLeft="true"
  49.             android:layout_centerVertical="true"
  51.             android:id="@+id/cardviewofuser"
  52.             app:cardCornerRadius="55dp"
  53.             >
  55.             <ImageView
  56.                 android:layout_width="match_parent"
  57.                 android:layout_height="match_parent"
  58.                 android:src="@drawable/ic_launcher_background"
  59.                 android:id="@+id/imageviewofuser"
  60.                 android:scaleType="centerCrop">
  62.             </ImageView>
  64.         </androidx.cardview.widget.CardView>
  66.         <RelativeLayout
  67.             android:layout_width="match_parent"
  68.             android:layout_height="0.1dp"
  69.             android:layout_marginLeft="10dp"
  70.             android:backgroundTint="#a6a6a6"
  71.             android:background="#a6a6a6"
  72.             android:layout_below="@id/cardviewofuser"
  73.             android:layout_toRightOf="@id/cardviewofuser"
  74.             android:layout_marginTop="-5dp" />
  76.     </RelativeLayout>
  78. </RelativeLayout>

用户模型

  1. package com.example.orbital;
  3. public class UserModel {
  4.    String Name, Contact, Address, Gender;
  6.     public UserModel(String Name, String Contact, String Address, String Gender) {
  7.         this.Name = Name;
  8.         this.Contact = Contact;
  9.         this.Address = Address;
  10.         this.Gender = Gender;
  11.     }
  13.     public UserModel() {
  14.     }
  16.     public String getName() {
  17.         return Name;
  18.     }
  20.     public void setName(String Name) {
  21.         this.Name = Name;
  22.     }
  24.     public String getContact() {
  25.         return Contact;
  26.     }
  28.     public void setContact(String Contact) {
  29.         this.Contact = Contact;
  30.     }
  32.     public String getAddress() {
  33.         return Address;
  34.     }
  36.     public void setAddress(String Address) {
  37.         this.Address = Address;
  38.     }
  40.     public String getGender() {
  41.         return Gender;
  42.     }
  44.     public void setGender(String Gender) {
  45.         this.Gender = Gender;
  46.     }
  47. }
Javaandroidandroid-recyclerviewfirebase

1条答案

按热度按时间
0yycz8jy

0yycz8jy1#

代码中的问题在于，您使用的recyclerview与布局文件中的不同。在chatfragment.xml文件中，您有：

  1. <androidx.recyclerview.widget.RecyclerView
  2.     android:layout_width="match_parent"
  3.     android:layout_height="match_parent"
  4.     android:id="@+id/recyclerview">
  5. </androidx.recyclerview.widget.RecyclerView>

在您的代码中，您正在使用：

  1. mRecyclerView = v.findViewById(R.id.recyclerView);

看到区别了吗？在布局文件中，id设置为 recyclerview 所有字母小写，而在代码中为 recyclerView 具有 W 大写，因此此行的nullpointerexception：

  1. mRecyclerView.setHasFixedSize(true);

要解决此问题，只需将上述代码行更改为：

  1. mRecyclerView = v.findViewById(R.id.recyclerview);
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