Android在recycleview片段选项卡布局消息中填充Firebase数据：E / RecyclerView：未连接适配器； 跳过布局

Question

I'm new with android firebase. My problem is that I would like to display the list of my data in the database in a recycleview. I have a tablayout that contains 3 tabs. it's in the first tab that I want to display my data, I use a fragment in which I met my recycleview, i also the method

Blockquote

addValueEventListener

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to take my firebase data. Whenever I launch the application it displays nothing I have this message

Blockquote

E / RecyclerView: No adapter attached; skip the layout

Blockquote

.Is this someone can help me. Thanks in Advance

My Firebase Data [1]: https://imgur.com/gallery/uIOEPuA

HomeActivity.java

 package com.example.saincurin.htfacile;

import android.os.Build;
import android.support.design.widget.NavigationView;
import android.support.design.widget.TabItem;
import android.support.design.widget.TabLayout;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.GravityCompat;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import com.example.saincurin.htfacile.Adapters.PageAdapter;

public class HomeActivity extends AppCompatActivity {

    private Toolbar toolbar;
    TabLayout tabLayout;
    ViewPager viewPager;
    private DrawerLayout mDrawer;
    private NavigationView nvDrawer;
    private ActionBarDrawerToggle drawerToggle;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        toolbar = findViewById(R.id.toolbar);
        mDrawer = findViewById(R.id.drawer_layout);
        nvDrawer = findViewById(R.id.nvView);
        tabLayout = findViewById(R.id.tabLayout);
        viewPager = findViewById(R.id.viewPager);

        toolbar.setTitle(getResources().getString(R.string.app_name));
        setSupportActionBar(toolbar);
        // Set up Drawer View



        PagerAdapter pagerAdapter = new PageAdapter(getSupportFragmentManager(), HomeActivity.this);
        viewPager.setAdapter(pagerAdapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            getWindow().setStatusBarColor(ContextCompat.getColor(HomeActivity.this,
                    R.color.colorAccent));
        }

        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, mDrawer, toolbar,
                R.string.drawer_open, R.string.drawer_close);
        mDrawer.addDrawerListener(toggle);
        toggle.syncState();

        // give the Tablayout the viewPager
        tabLayout.setupWithViewPager(viewPager);
//        setupDrawerContent(nvDrawer);
    }

    @Override
    public void onBackPressed() {
        if (mDrawer.isDrawerOpen(GravityCompat.START)) {
            mDrawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    //    private void setupDrawerContent(NavigationView navigationView) {
//        navigationView.setNavigationItemSelectedListener(
//                new NavigationView.OnNavigationItemSelectedListener() {
//                    @Override
//                    public boolean onNavigationItemSelected(MenuItem menuItem) {
//                        selectDrawerItem(menuItem);
//                        return true;
//                    }
//                });
//    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_products, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.action_more) {
            Toast.makeText(this, "The more is selected", Toast.LENGTH_SHORT).show();
        }else if (item.getItemId() == R.id.action_search) {
            Toast.makeText(this, "The search is selected", Toast.LENGTH_SHORT ).show();
        }else if (item.getItemId() == R.id.drawer_layout) {
            mDrawer.openDrawer(GravityCompat.START);
        }
        return true;
    }
}

My Model

package com.example.saincurin.htfacile.ModelData;

public class DataModel {

    private String  description;
    private String name;
    private String image;
    private String price;
    private String quantity;


    //constructor
    public DataModel() {

    }

    public DataModel(String name, /*String description,*/ String image, String price) {
        this.name = name;
//        this.description = description;
        this.image = image;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getQuantity() {
        return quantity;
    }

    public void setQuantity(String quantity) {
        this.quantity = quantity;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }
}

My Adapter

package com.example.saincurin.htfacile.Adapters;

import android.content.Context;
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.ImageView;
import android.widget.TextView;

import com.example.saincurin.htfacile.ModelData.DataModel;
import com.example.saincurin.htfacile.R;
import com.squareup.picasso.Picasso;

import java.util.List;


// Create the basic adapter extending from RecyclerView.Adapter
// Note that we specify the custom ViewHolder which gives us access to our views

public class ProductsAdapter extends RecyclerView.Adapter<ProductsAdapter.ProductsviewHolder> {
    private Context mcontext;
    // Store a member variable for the contacts
    private List<DataModel> mDataModel;

    public ProductsAdapter(Context context, List<DataModel> mDataModel) {
        mcontext = context;
        this.mDataModel = mDataModel;
    }


    // Usually involves inflating a layout from XML and returning the holder
    @NonNull
    @Override
    public ProductsviewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        //inflate the custom Layout
        View dataView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_row, parent, false);

        //return a new holder instance
        return new  ProductsviewHolder(dataView);


    }

    // Involves populating data into the item through holder
    @Override
    public void onBindViewHolder(@NonNull ProductsviewHolder holder, int position) {
        // Get the data model based on position
        DataModel dataModel = mDataModel.get(position);

        // Set item views based on your views and data model
        holder.txtName.setText(dataModel.getName());
//        holder.txtDescription.setText(dataModel.getDescription());
        holder.txtPrice.setText(dataModel.getPrice());
        Picasso.with(mcontext)
                .load(dataModel.getImage())
                .fit()
                .centerCrop()
                .into(holder.imageView);

    }

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

    // Provide a direct reference to each of the views within a data item
    // Used to cache the views within the item layout for fast access
    public class ProductsviewHolder extends RecyclerView.ViewHolder {
        public TextView txtName;
//        public TextView txtDescription;
        public TextView txtPrice;
        public TextView txtQuantity;
        public ImageView imageView;


        // We also create a constructor that accepts the entire item row
        // and does the view lookups to find each subview
        public ProductsviewHolder(View itemView) {

            // Stores the itemView in a public final member variable that can be used
            // to access the context from any ViewHolder instance.
            super(itemView);

            txtName = itemView.findViewById(R.id.rvTitleTv);
//            txtDescription = itemView.findViewById(R.id.rDescriptionTv);
            txtPrice = itemView.findViewById(R.id.rPrice);
            imageView = itemView.findViewById(R.id.rImageView);

        }
    }


}

My first Fragment tab

package com.example.saincurin.htfacile.fragments;


import android.content.Context;
import android.os.Bundle;
import android.support.annotation.NonNull;
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 android.widget.Toast;

import com.example.saincurin.htfacile.Adapters.ProductsAdapter;
import com.example.saincurin.htfacile.ModelData.DataModel;
import com.example.saincurin.htfacile.R;
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 java.util.ArrayList;
import java.util.List;

/**
 * A simple {@link Fragment} subclass.
 */
public class ProductsFragment extends Fragment {

    private RecyclerView mRecycleView;
    private ProductsAdapter mProductsAdapter;

    private DatabaseReference mReference;
    private List<DataModel> mDataModel;

    View v;

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


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

        //RecycleView
        mRecycleView = v.findViewById(R.id.recycleView);
        mRecycleView.setHasFixedSize(true);
        //set Layout as LinearLayout
        mRecycleView.setLayoutManager(new LinearLayoutManager(getContext()));

        mDataModel = new ArrayList<>();


        //send Query FirebaseDatabase
       mReference = FirebaseDatabase.getInstance().getReference("uploads");

        Log.e("DEBUG", "The Reference :"+mReference);

        mReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                    DataModel dataModel = postSnapshot.getValue(DataModel.class);
                    mDataModel.add(dataModel);
                }
//                Log.e("DEBUG","The data model "+ mDataModel.toString());
                mProductsAdapter = new ProductsAdapter(getContext(), mDataModel);
//                Log.e("DEBUG","The data model "+ mProductsAdapter);

                //set the adapter to the recyclerview
                mRecycleView.setAdapter(mProductsAdapter);
                mProductsAdapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Toast.makeText(getContext(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
            }
        });


        return v;
    }

}

Layout for my first tab pager

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".fragments.ProductsFragment">

    <!--RecycleView-->
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycleView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</FrameLayout>

Layout for my HomeActivity

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context=".HomeActivity"
    tools:openDrawer="start">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="?attr/colorPrimary"
            android:minHeight="?attr/actionBarSize"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:theme="@style/ThemeOverlay.AppCompat.Dark" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tabLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/toolbar"
            style="@style/myCustomTabLayout"
            android:background="@color/colorPrimary"
            app:tabSelectedTextColor="@android:color/white"
            app:tabTextColor="@android:color/black">
        </android.support.design.widget.TabLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nvView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@android:color/white"
        app:headerLayout="@layout/nav_header"
        app:menu="@menu/drawer_view" />
</android.support.v4.widget.DrawerLayout>

My item_row.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:cardBackgroundColor="#fff"
    app:cardCornerRadius="3dp"
    app:cardElevation="3dp"
    app:cardUseCompatPadding="true"
    app:contentPadding="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/rvTitleTv"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Title"
            android:textColor="#000"
            android:textSize="22sp"
            android:textStyle="bold" />

        <ImageView
            android:id="@+id/rImageView"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:adjustViewBounds="true"
            android:background="@drawable/loading"
            android:scaleType="center" />

        <TextView
            android:id="@+id/rPrice"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="150 gdes"
            android:textSize="20dp"
            android:textStyle="bold" />

        <!--<TextView-->
            <!--android:id="@+id/rDescriptionTv"-->
            <!--android:layout_width="match_parent"-->
            <!--android:layout_height="wrap_content"-->
            <!--android:text="This is the post description that"-->
            <!--android:textSize="20sp" />-->
    </LinearLayout>

</android.support.v7.widget.CardView>

Answer 1

Welcome to StackOverflow. The RecyclerView is quite specific when it comes to its setup. So you need to make sure you set up the adapter before setting the layout manager and the fixedSize property.

Try changing your onCreateView method to this:

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

    // Notice that I changed the order of RecyclerView setup
    mRecycleView = v.findViewById(R.id.recycleView);
    mDataModel = new ArrayList<>();
    mProductsAdapter = new ProductsAdapter(getContext(), mDataModel);
    mRecyclerView.setAdapter(mProductsAdapter);
    mRecycleView.setHasFixedSize(true);
    //set Layout as LinearLayout
    mRecycleView.setLayoutManager(new LinearLayoutManager(getContext()));

    //send Query FirebaseDatabase
    mReference = FirebaseDatabase.getInstance().getReference("uploads");

    mReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                DataModel dataModel = postSnapshot.getValue(DataModel.class);
                mDataModel.add(dataModel);
            }

            mProductsAdapter.notifyDataSetChanged();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(getContext(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
        }
    });

    return v;
}