How to properly highlight selected item on Android RecyclerView?

AndroidApps/ApplicationsMobile Development

This example demonstrates how do I properly highlight the selected item on android 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.

Add the following dependency in the build.gradle (Module: app)

implementation 'com.android.support:recyclerview-v7:28.0.0'

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

<?xml version="1.0" encoding="utf-8"?>
<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"
   android:padding="4dp"
   tools:context=".MainActivity">
   <androidx.recyclerview.widget.RecyclerView
      android:id="@+id/recyclerView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingBottom="8dp" />
</RelativeLayout>

Step 3 − Create a layout resource file (list_layout.xml) and add the following code −

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/container"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:background="@drawable/background_selector"
   android:padding="16dp">
   <TextView
      android:id="@+id/awardTitle"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_marginTop="10dp"
      android:text="New Text"
      android:textSize="18sp"
      android:textStyle="bold" />
   <TextView
      android:id="@+id/awardYear"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@+id/awardTitle"
      android:layout_alignStart="@+id/awardTitle"
      android:layout_marginTop="20dp"
      android:text="New Text"
      android:textColor="#000" />
   <TextView
      android:id="@+id/playerName"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentEnd="true"
      android:text="New Text" />
</RelativeLayout>

Step 4 − Create drawable resource files as mentioned below and add the respective codes −

background_selector.xml −

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:drawable="@color/colorAccent" android:state_pressed="false" android:state_selected="true" />
   <item android:drawable="@android:color/white" android:state_selected="false" />
</selector>

line_divider.xml −

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
   <size
      android:width="2dp"
      android:height="2dp" />
   <solid android:color="@color/colorPrimaryDark" />
</shape>

Step 5 − Create java class files as mentioned below and add the respective codes −

ItemObject 

class ItemObject {
   private String awardTitle;
   private String awardYear;
   private String player;
   ItemObject(String awardTitle, String awardYear, String player) {
      this.awardTitle = awardTitle;
      this.awardYear = awardYear;
      this.player = player;
   }
   String getAwardTitle() {
      return awardTitle;
   }
   String getAwardYear() {
      return awardYear;
   }
   String getPlayer() {
      return player;
   }
}

RecyclerViewAdapter −

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
public class RecyclerViewAdapter extends
RecyclerView.Adapter<RecyclerViewHolders> {
   private List<ItemObject> itemList;
   RecyclerViewAdapter(Context context, List<ItemObject> itemList) {
      this.itemList = itemList;
   }
   @NonNull
   @Override
   public RecyclerViewHolders onCreateViewHolder(ViewGroup parent, int viewType) {
      View layoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_layout, null);
      return new RecyclerViewHolders(layoutView);
   }
   @Override
   public void onBindViewHolder(RecyclerViewHolders holder, int position) {
      holder.awardTitle.setText("Award Title: " + itemList.get(position).getAwardTitle());
      holder.awardYear.setText("Award Year: " + itemList.get(position).getAwardYear());
      holder.player.setText("Player Name: " + itemList.get(position).getPlayer());
   }
   @Override
   public int getItemCount() {
      return this.itemList.size();
   }
}

RecyclerViewHolders

import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;
class RecyclerViewHolders extends RecyclerView.ViewHolder implements
View.OnClickListener {
   TextView awardTitle;
   TextView awardYear;
   TextView player;
   private SparseBooleanArray selectedItems = new SparseBooleanArray();
   RecyclerViewHolders(View itemView) {
      super(itemView);
      itemView.setOnClickListener(this);
      awardTitle = itemView.findViewById(R.id.awardTitle);
      awardYear = itemView.findViewById(R.id.awardYear);
      player = itemView.findViewById(R.id.playerName);
   }
   @Override
   public void onClick(View view) {
      if (selectedItems.get(getAdapterPosition(), false)) {
         selectedItems.delete(getAdapterPosition());
         view.setSelected(false);
      }
       else {
         selectedItems.put(getAdapterPosition(), true);
         view.setSelected(true);
      }
   }
}

SimpleItemDecoration 

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.core.content.ContextCompat;
import androidx.recyclerview.widget.RecyclerView;
class SimpleItemDecoration extends RecyclerView.ItemDecoration {
   private Drawable drawable;
   SimpleItemDecoration(Context context) {
      drawable = ContextCompat.getDrawable(context, R.drawable.line_divider);
   }
   @Override
   public void onDrawOver(@NonNull Canvas canvas, RecyclerView parent, @NonNull RecyclerView.State state) {
      int left = parent.getPaddingLeft();
      int right = parent.getWidth() - parent.getPaddingRight();
      int childCount = parent.getChildCount();
      for (int i = 0; i < childCount; i++) {
         View child = parent.getChildAt(i);
         RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
         int top = child.getBottom() + params.bottomMargin;
         int bottom = top + drawable.getIntrinsicHeight();
         drawable.setBounds(left, top, right, bottom);
         drawable.draw(canvas);
      }
   }
}

Step 6 − Add the following code to src/MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      RecyclerView recyclerView = findViewById(R.id.recyclerView);
      recyclerView.addItemDecoration(new SimpleItemDecoration(this));
      LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
      recyclerView.setLayoutManager(layoutManager);
      List<ItemObject> posts = returnListItems();
      RecyclerViewAdapter adapter = new RecyclerViewAdapter(MainActivity.this, posts);
      recyclerView.setAdapter(adapter);
   }
   private List<ItemObject> returnListItems() {
      List<ItemObject> items = new ArrayList<>();
      items.add(new ItemObject("Ballon'd'or", "2007", "Ricardo KaKa"));
      items.add(new ItemObject("Ballon'd'or", "2008", "Cristiano Ronaldo"));
      items.add(new ItemObject("Ballon'd'or", "2009 - 2012, 2015", "Lionel Messi"));
      items.add(new ItemObject("Ballon'd'or", "2013, 2014, 2016, 2017", "Cristiano Ronaldo"));
      items.add(new ItemObject("Ballon'd'or", "2018", "Luca Modric"));
      items.add(new ItemObject("Ballon'd'or", "2019", "Haven't decided yet"));
      return items;
   }
}

Step 7 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

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 the 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 −

Click here to download the project code.

raja
Published on 21-Nov-2019 10:12:22
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