Ошибки и приложения продолжают разбиваться при отображении данных с использованием FirebaseRecyclerVIewAdapter и ошибки:

Question

Я слежу за видео на YouTube, чтобы создать проект Firebase для отображения содержимого FireBase в представлении переработчика. Но я застрял, потому что приложение аварийно завершает работу, показывая ошибку, поскольку макет ограничения не может быть приведен к представлению переработчика. Я делюсь всеми кодами, которые я использовал в этом проекте (в частности, связанные с этой ошибкой), пожалуйста, помогите мне с этим проектом

xml код: frag_home. xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:layout_width="409dp"
        android:layout_height="729dp"
        android:layout_marginStart="1dp"
        android:layout_marginTop="1dp"
        android:layout_marginEnd="1dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recycler_menu"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

java код (MainHome. java)

package com.example.authentication;

import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;
import com.example.authentication.Model.Products;
import com.example.authentication.ViewHolder.ProductViewHolder;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.navigation.NavigationView;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.squareup.picasso.Picasso;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.core.view.GravityCompat;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.navigation.NavController;
import androidx.navigation.NavDestination;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import de.hdodenhof.circleimageview.CircleImageView;

public class MainHome extends AppCompatActivity {
    CircleImageView ProfileImage;
    TextView UserName;
    FirebaseUser user;
    DatabaseReference userName;
    String username;
    String uid;
    private DatabaseReference mDatabase;
    private DatabaseReference booksRef;
    private AppBarConfiguration mAppBarConfiguration;
    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_home);

        booksRef = FirebaseDatabase.getInstance().getReference().child("Books");
        mDatabase = FirebaseDatabase.getInstance().getReference();
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        final DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow,
                R.id.nav_tools, R.id.nav_share, R.id.nav_send)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);


        View headerView = navigationView.getHeaderView(0);

        //For Product Display
        recyclerView = (RecyclerView) findViewById(R.id.recycler_menu);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setHasFixedSize(true);


        //For Profile display
        ProfileImage = headerView.findViewById(R.id.settings_profile_image);
        UserName = headerView.findViewById(R.id.userName);

        user = FirebaseAuth.getInstance().getCurrentUser();
        uid = user.getUid();
        userName = FirebaseDatabase.getInstance().getReference().child("users").child(uid); //Username storage refernce

        if (user.getPhotoUrl() != null) {
            Glide.with(this).load(user.getPhotoUrl()).into(ProfileImage);
        }

        userName.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists()) {
                    username = dataSnapshot.child("username").getValue().toString();
                    UserName.setText(username);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });


        navController.addOnDestinationChangedListener(new NavController.OnDestinationChangedListener() {
            @Override
            public void onDestinationChanged(@NonNull NavController controller, @NonNull NavDestination destination, @Nullable Bundle arguments) {
                int id = destination.getId();

                switch (destination.getId()) {
                    case R.id.nav_home:
                        Toast.makeText(MainHome.this, "Buy Book Fragmet", Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.nav_gallery:
                        finish();
                        Toast.makeText(MainHome.this, "Sell Book Fragmet", Toast.LENGTH_SHORT).show();
                        if (drawer.isDrawerOpen(GravityCompat.START)) {
                            drawer.closeDrawer(GravityCompat.START);
                        }
                        Intent sellIntent = new Intent(MainHome.this, Add_Product.class);
                        startActivity(sellIntent);
                        break;
                    case R.id.nav_slideshow:
                        //finish();
                        Toast.makeText(MainHome.this, "Cart fragment", Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.nav_tools:
                        Toast.makeText(MainHome.this, "Order fragment", Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.nav_send:
                        finish();
                        Toast.makeText(MainHome.this, "Setting Fragment", Toast.LENGTH_SHORT).show();
                        if (drawer.isDrawerOpen(GravityCompat.START)) {
                            drawer.closeDrawer(GravityCompat.START);
                        }
                        Intent settingIntent = new Intent(MainHome.this, SettingActivity.class);
                        startActivity(settingIntent);
                        break;
                    case R.id.nav_share:
                        if (drawer.isDrawerOpen(GravityCompat.START)) {
                            drawer.closeDrawer(GravityCompat.START);
                        }
                        finish();
                        Intent logoutIntent = new Intent(MainHome.this, LoginActivity.class);
                        startActivity(logoutIntent);
                        FirebaseAuth.getInstance().signOut();
                        break;
                    default:
                        break;
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_home, menu);
        return true;
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        return NavigationUI.navigateUp(navController, mAppBarConfiguration)
                || super.onSupportNavigateUp();
    }

    public void onStart() {

        super.onStart();
        FirebaseRecyclerOptions<Products> options = new  FirebaseRecyclerOptions.Builder<Products>().setQuery(booksRef,Products.class).build();

        FirebaseRecyclerAdapter<Products, ProductViewHolder>  adapter =
                new FirebaseRecyclerAdapter<Products, ProductViewHolder>(options) {
                    @Override
                    protected void onBindViewHolder(@NonNull ProductViewHolder holder, int position, @NonNull Products model) {
                        holder.product_name.setText(model.getBname());
                        holder.product_description.setText(model.getDescription());
                        holder.product_price.setText("Price:" + model.getPrice() + "Rs");
                        holder.posted_email.setText(model.getUser_email());
                        holder.posted_date.setText(model.getDate());
                        Picasso.get().load(model.getImage()).into(holder.product_image);
                    }

                    @NonNull
                    @Override
                    public ProductViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_listner,parent,false);
                        ProductViewHolder holder = new ProductViewHolder(view);
                        return holder;
                    }
                };
       recyclerView.setAdapter(adapter);
       adapter.startListening();
    }

}

Элементы, которые я хочу отобразить в представлении переработчика

file name : item_listner.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="348dp"
        android:layout_marginTop="20dp"
        android:layout_marginStart="10dp"
        android:layout_marginEnd="10dp"
        app:cardElevation="15dp">


        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="333dp">

            <TextView
                android:id="@+id/product_name"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Product Name"
                android:textAlignment="center"
                android:textColor="@color/colorPrimary"
                android:textSize="20dp"
                android:textStyle="bold" />

            <ImageView
                android:id="@+id/product_image"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_below="@+id/product_name"
                android:layout_marginTop="2dp"
                android:scaleType="centerCrop" />

            <TextView
                android:id="@+id/product_price"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@+id/product_image"
                android:text="Product Price"
                android:textAlignment="center"
                android:textColor="@color/colorPrimaryDark"
                android:textSize="18dp" />

            <TextView
                android:id="@+id/product_description"
                android:layout_width="match_parent"
                android:layout_height="44dp"
                android:layout_below="@+id/product_price"
                android:layout_marginTop="2dp"
                android:paddingTop="10dp"
                android:text="Product Description"
                android:textAlignment="center"
                android:textColor="@color/colorPrimaryDark"
                android:textSize="16dp" />

            <TableRow
                android:id="@+id/table"
                android:layout_width="match_parent"
                android:layout_height="32dp"
                android:layout_below="@id/product_description">

                <TextView
                    android:id="@+id/textView21"
                    android:layout_width="68dp"
                    android:layout_height="match_parent"
                    android:paddingTop="6dp"
                    android:text="  Posted:"
                    android:textColor="@color/colorPrimary" />

                <TextView
                    android:id="@+id/posted_email"
                    android:layout_width="167dp"
                    android:layout_height="match_parent"
                    android:paddingTop="6dp"
                    android:text=" tejasgudulekar2@gmail.com"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="12sp" />

                <TextView
                    android:id="@+id/posted_date"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:paddingTop="6dp"
                    android:text=" 31'Feb 2020"
                    android:textColor="@color/colorPrimaryDark"
                    android:textSize="12sp" />

                <Button
                    android:id="@+id/cart_button"
                    android:layout_width="74dp"
                    android:layout_height="34dp"
                    android:text="Added"
                    android:textColor="@color/colorPrimary" />

            </TableRow>
        </RelativeLayout>
    </androidx.cardview.widget.CardView>

</LinearLayout>

Logcat:

2 14826-14826/com.example.authentication E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.authentication, PID: 14826
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.authentication/com.example.authentication.MainHome}: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to androidx.recyclerview.widget.RecyclerView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2747)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2808)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1541)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:165)
        at android.app.ActivityThread.main(ActivityThread.java:6375)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:802)
     Caused by: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to androidx.recyclerview.widget.RecyclerView
        at com.example.authentication.MainHome.onCreate(MainHome.java:92)
        at android.app.Activity.performCreate(Activity.java:6845)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2700)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2808) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1541) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:165) 
        at android.app.ActivityThread.main(ActivityThread.java:6375) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:802) 

Answer 1

вы установили activity_main_home макет для класса MainHome, поэтому

recyclerView = (RecyclerView) findViewById(R.id.recycler_menu);

, используя эту строку, вы пытаетесь получить recyclerView из activity_main_home, который необходимо проверить, если есть и существует ли recyclerView с таким же идентификатором или нет.