Question

当我尝试从Firestore访问数据并将其显示在listview片段类中时，我的应用程序崩溃。任何帮助对我来说都是有益的

availablestudent_fragment.java（主要片段类）

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

{ {2}}

logcat_Error（当我尝试单击片段时，我的应用程序崩溃了）

<?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>

从单元格检索错误以使其更加清晰

Answer 1

要解决此问题，您需要根据Java Naming Conventions将Users类中的字段和方法的大小写固定。因此，您的模型类应如下所示：

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，一切正常。

当我尝试从Firestore提取数据并显示在listview片段中时，我的应用程序崩溃

1 个答案: