Q:

recyclerview not loading adapter values in a fragment

I have a base navigation drawer activity, which will load a fragment. The fragment. The fragment has a recycler view in its layout. The recycler view has an adapter which use Glide to load images from internet. I'm not able to get the image loaded. (Have added the Internet permission in manifest). 
My Base activity is: 
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.RelativeLayout;
import android.widget.Toast;

public class BaseActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, Item1Fragment.OnFragmentInteractionListener {

    /**
     * Frame layout: Which is going to be used as parent layout for child activity layout.
     * This layout is protected so that child activity can access this
     */
    protected RelativeLayout relativeLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        relativeLayout = (RelativeLayout) findViewById(R.id.content_frame);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_base);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        //Add the Very First i.e Squad Fragment to the Container
        Fragment item1Fragment = new Item1Fragment();
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.add(R.id.content_frame, item1Fragment, null);
        fragmentTransaction.commit();
    }

    @Override
    public void onFragmentInteraction(Uri uri) {

    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        FragmentTransaction fragmentTransaction = this.getSupportFragmentManager().beginTransaction();
        if (id == R.id.nav_camera) {
            Fragment item1Fragment = new Item1Fragment();
            fragmentTransaction.replace(R.id.content_frame, item1Fragment);
            fragmentTransaction.commit();
        } else if (id == R.id.nav_gallery) {
            Fragment item2Fragment = new Item2Fragment();
            fragmentTransaction.replace(R.id.content_frame, item2Fragment);
            fragmentTransaction.commit();
        } else if (id == R.id.nav_slideshow) {
            Toast.makeText(getApplicationContext(), "333", Toast.LENGTH_SHORT).show();
        } else if (id == R.id.nav_manage) {
            Toast.makeText(getApplicationContext(), "444", Toast.LENGTH_SHORT).show();
        } else if (id == R.id.nav_share) {
            Toast.makeText(getApplicationContext(), "555", Toast.LENGTH_SHORT).show();
        } else if (id == R.id.nav_send) {
            Toast.makeText(getApplicationContext(), "666", Toast.LENGTH_SHORT).show();
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }

    // Container Activity must implement this interface
    public interface OnHeadlineSelectedListener {
        public void onArticleSelected(int position);
    }
}

Activity layout is:
<?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" android:background="@color/colorPrimary"
    tools:openDrawer="start">

    <RelativeLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <include
        layout="@layout/app_bar_base"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_base"
        app:menu="@menu/activity_base_drawer" />
</android.support.v4.widget.DrawerLayout>

Fragment:
import android.content.Context;
import android.content.res.Configuration;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.ArrayList;

public class Item1Fragment extends Fragment {

    private OnFragmentInteractionListener mListener;
    private ArrayList<ImageModel> data = new ArrayList<>();
    private GalleryAdapter mAdapter;
    private RecyclerView mRecyclerView;

    public static String IMGS[] = {
            "https://images.unsplash.com/photo-1444090542259-0af8fa96557e?q=80&fm=jpg&w=1080&fit=max&s=4b703b77b42e067f949d14581f35019b",
            "https://images.unsplash.com/photo-1439546743462-802cabef8e97?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1441155472722-d17942a2b76a?q=80&fm=jpg&w=1080&fit=max&s=80cb5dbcf01265bb81c5e8380e4f5cc1",
            "https://images.unsplash.com/photo-1437651025703-2858c944e3eb?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1431538510849-b719825bf08b?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1434873740857-1bc5653afda8?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1439396087961-98bc12c21176?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1433616174899-f847df236857?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1438480478735-3234e63615bb?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300",
            "https://images.unsplash.com/photo-1438027316524-6078d503224b?dpr=2&fit=crop&fm=jpg&h=725&q=50&w=1300"
    };

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        for (int i = 0; i < IMGS.length; i++) {

            ImageModel imageModel = new ImageModel();
            imageModel.setName("Image " + i);
            imageModel.setUrl(IMGS[i]);
            data.add(imageModel);
        }

        View view = inflater.inflate(R.layout.fragment_item1,container,false);
        mRecyclerView = (RecyclerView)view.findViewById(R.id.list);
        if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE) {
            mRecyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 3));
        }else{
            mRecyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2));
        }

        mRecyclerView.setHasFixedSize(true);
        mAdapter = new GalleryAdapter(getActivity().getApplicationContext(), data);
        mRecyclerView.setAdapter(mAdapter);

        return view;
    }

    //
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

fragment layout:
<RelativeLayout 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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context="com.akl.nav2.Item1Fragment">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/list" android:background="#FFBB00"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</RelativeLayout>

Adapter:
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.engine.DiskCacheStrategy;

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

/**
 * Created by akl on 3/12/2016.
 */
public class GalleryAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    Context context;
    List<ImageModel> data = new ArrayList<>();

    public GalleryAdapter(Context context, List<ImageModel> data) {
        this.context = context;
        this.data = data;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        RecyclerView.ViewHolder viewHolder;
        View v;
        v = LayoutInflater.from(parent.getContext()).inflate(
                R.layout.list_item, parent, false);
        viewHolder = new MyItemHolder(v);

        return viewHolder;
    }

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

        Glide.with(context).load(data.get(position).getUrl())
                .thumbnail(0.5f)
                .override(200, 200)
                .crossFade()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(((MyItemHolder) holder).mImg);
    }

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

    public static class MyItemHolder extends RecyclerView.ViewHolder {
        ImageView mImg;

        public MyItemHolder(View itemView) {
            super(itemView);

            mImg = (ImageView) itemView.findViewById(R.id.item_img);
        }
    }
}

Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.akl.nav2">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".BaseActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category
                    android:name="android.intent.category.LAUNCHER"
                    android:theme="@style/AppTheme.NoActionBar" />
            </intent-filter>
        </activity>

    </application>
    <uses-permission android:name="android.permission.INTERNET" />
</manifest>

A:

The code was fine. A clean build as suggested by @HoangNguyen was enough to make the code run.

