How to use Constraint Layout with recyclerview?

This example demonstrate about How to use Constraint Layout with recyclerview

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.design.widget.CoordinatorLayout android:layout_width = "match_parent"
   android:layout_height = "match_parent"
   xmlns:android = "http://schemas.android.com/apk/res/android"
   xmlns:app = "http://schemas.android.com/apk/res-auto">
   <android.support.design.widget.AppBarLayout
      android:layout_width = "match_parent"
      android:layout_height = "wrap_content">
      <android.support.v7.widget.Toolbar
         android:id = "@+id/appbarlayout_tool_bar"
         android:background = "@color/colorPrimary"
         android:layout_width = "match_parent"
         android:layout_height = "?attr/actionBarSize"
         app:layout_scrollFlags = "scroll|snap|enterAlways"
         app:theme = "@style/ThemeOverlay.AppCompat.Dark.ActionBar"
         app:popupTheme = "@style/ThemeOverlay.AppCompat.Light" />
   </android.support.design.widget.AppBarLayout>
   <android.support.v7.widget.RecyclerView
      android:id = "@+id/recycler_view"
      android:layout_width = "match_parent"
      android:layout_height = "match_parent"
      app:layout_behavior = "@string/appbar_scrolling_view_behavior"/>
</android.support.design.widget.CoordinatorLayout>

In the above code, we have taken app bar layout and recycler view.

Step 3 − Add the following code to src/MainActivity.java

<?xml version = "1.0" encoding = "utf-8"?>
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.content.pm.ShortcutInfoCompat;
import android.support.v4.content.pm.ShortcutManagerCompat;
import android.support.v4.graphics.drawable.IconCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import android.support.v7.widget.Toolbar;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
   private RecyclerView recyclerView;
   private customAdapter mAdapter;
   TextView text;
   ArrayList<String> list = new ArrayList<>();
   @TargetApi(Build.VERSION_CODES.LOLLIPOP)
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Toolbar toolbar = (android.support.v7.widget.Toolbar)findViewById(R.id.appbarlayout_tool_bar);
      toolbar.setTitle("This is toolbar.");
      setSupportActionBar(toolbar);
      recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
      RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
      recyclerView.setLayoutManager(mLayoutManager);
      recyclerView.setItemAnimator(new DefaultItemAnimator());
      mAdapter = new customAdapter(this,list);
      recyclerView.setAdapter(mAdapter);
      recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), DividerItemDecoration.VERTICAL));
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
      list.add("Krishna");
      list.add("prasad");
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
      list.add("sairamm");
      list.add("Krishna");
      list.add("prasad");
   }
}

Step 4 − Add the following code to Manifest.xml

<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
   package = "com.example.myapplication">
   <uses-permission android:name = "android.permission.INTERNET" />
   <uses-permission android:name = "com.android.launcher.permission.INSTALL_SHORTCUT" />
   <application
      android:allowBackup = "true"
      android:theme = "@style/AppTheme.NoActionBar"
      android:icon = "@mipmap/ic_launcher"
      android:label = "@string/app_name"
      android:roundIcon = "@mipmap/ic_launcher_round"
      android:supportsRtl = "true">
      <activity
         android:name = ".MainActivity"
         android:configChanges = "keyboardHidden|orientation|screenSize">
         <intent-filter>
            <action android:name = "android.intent.action.MAIN" />
            <action android:name = "android.intent.action.CREATE_SHORTCUT" />
            <category android:name = "android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Step 5 − Add the following code to customAdapter.java

<?xml version = "1.0" encoding = "utf-8"?>
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.TextView;
import java.util.ArrayList;

public class customAdapter extends RecyclerView.Adapter<customAdapter.MyViewHolder> {
   Context context;
   ArrayList<String> list;
   public class MyViewHolder extends RecyclerView.ViewHolder {
      public TextView title;
      public MyViewHolder(View view) {
         super(view);
         title = (TextView) view.findViewById(R.id.title);
      }
   }
   public customAdapter(Context context, ArrayList<String> list) {
      this.context = context;
      this.list = list;
   }
   @NonNull
   @Override
   public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
      View itemView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.list_row, viewGroup, false);
      return new MyViewHolder(itemView);
   }
   @Override
   public void onBindViewHolder(@NonNull MyViewHolder myViewHolder, int i) {
      myViewHolder.title.setText(list.get(i));
   }
   @Override
   public int getItemCount() {
      return list.size();
   }
}

Step 6 − Add the following code to list_row.xml

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.constraint.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 = "wrap_content"
   android:background = "@color/colorAccent"
   tools:context = ".MainActivity">
   <ImageView
      android:id = "@+id/imageView2"
      android:layout_width = "wrap_content"
      android:layout_height = "wrap_content"
      android:src = "@drawable/logo"
      app:layout_constraintBottom_toBottomOf = "parent"
      app:layout_constraintEnd_toEndOf = "parent"
      app:layout_constraintStart_toStartOf = "parent"
      app:layout_constraintTop_toTopOf = "parent"
      app:layout_constraintVertical_bias = "0.209" />
   <TextView
      android:id = "@+id/title"
      android:layout_width = "match_parent"
      android:layout_height = "wrap_content"
      android:layout_marginTop = "35dp"
      android:gravity = "center"
      android:textSize = "30sp"
      app:layout_constraintTop_toBottomOf = "@+id/imageView2"
      tools:layout_editor_absoluteX = "0dp" />
   <TextView
      android:id = "@+id/textview2"
      android:layout_width = "match_parent"
      android:layout_height = "wrap_content"
      android:layout_marginTop = "16dp"
      android:layout_marginBottom = "8dp"
      android:gravity = "center"
      android:text = "Sairamkrishan"
      android:textSize = "30sp"
      app:layout_constraintBottom_toBottomOf = "parent"
      app:layout_constraintTop_toBottomOf = "@+id/title"
      app:layout_constraintVertical_bias = "0.0"
      tools:layout_editor_absoluteX = "0dp" />
</android.support.constraint.ConstraintLayout>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –