RecyclerView in Android with Java

In this row_layout.xml file, we create an ImageView and TextView for every row of the RecyclerView. The design of the row of RecyclerView is shown in the figure below.

Step 6. The RecyclerView, which we will create, will show the list of some randomly chosen programming languages. We need a class that represents a single RecyclerView item data to create a file named Data.java. The code of this Data.java file is listed below.

public class Data {  
  
    public String name;  
  
    public String getName() {  
        return name;  
    }  
  
    public void setName(String name) {  
        this.name = name;  
    }  
  
    public int getImageId() {  
        return imageId;  
    }  
  
    public void setImageId(int imageId) {  
        this.imageId = imageId;  
    }  
  
    public int imageId;  
  
    Data(String name, int imageId) {  
        this.name = name;  
        this.imageId = imageId;  
    }  
} 

In this Data.java class file, we create a public constructor for the image, the name of the programming language, and the setter and getter method for these variables.

Step 7. In this step, we will create a custom RecyclerView.Adapter file named RecyclerView_Adapter.java. The RecyclerView.Adapter is similar to the adapters used on a ListView, but with performance improvement, ViewHolder provided.

A ListView has adapters for various sources, such as ArrayAdapter for arrays and CursorAdapter for the output of databases. The RecyclerView.Adapter requires a custom implementation to supply the adapter with data.

The code file of RecyclerVIew_Adapter.java is listed below.

import android.app.Application;  
import android.content.Context;  
import android.view.LayoutInflater;  
import android.view.View;  
import android.view.ViewGroup;  
  
import androidx.annotation.NonNull;  
import androidx.recyclerview.widget.RecyclerView;  
import java.util.Collections;  
import java.util.List;  
  
public class RecyclerView_Adapter extends RecyclerView.Adapter<View_Holder> {  
  
    List<Data> list = Collections.emptyList();  
    Context context;  
  
    public RecyclerView_Adapter(List<Data> data, Application application) {  
        this.list = data;  
        this.context = application;  
    }  
  
    @NonNull  
    @Override  
    public View_Holder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {  
        //Inflate the layout, initialize the View Holder  
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_layout, parent, false);  
        View_Holder holder = new View_Holder(v);  
        return holder;  
    }  
  
    @Override  
    public void onBindViewHolder(@NonNull View_Holder holder, int position) {  
  
        //Use the provided View Holder on the onCreateViewHolder method to populate the current row on the RecyclerView  
        holder.name.setText(list.get(position).name);  
        holder.imageView.setImageResource(list.get(position).imageId);  
  
    }  
  
    @Override  
    public int getItemCount() {  
        return list.size();  
    }  
} 

In this recyclerView_Adapter.java file, we extend RecyclerView.Adapter and create its constructor. It shows an error, so we have to implement its methods onCreateViewHolder(), onBindViewHolder(), and getItemCount().

• onCreateViewHolder()- It inflates the row layout and initializes the view holder. It handles findViewById) (methods, find views once and recycle them so that repetitive calls are avoided.

• onBindViewHolder()- It uses the onCreateViewHolder() View Holder to fill in the current RecyclerView row with data.

• getItemCount()- This method returns the collection size, which contains the items that we wish to show

Step 8. Now, we will create a ViewHolder class named View_Holder.java Java file because, for the one entry in the RecyclerView, the RecyclerView uses a ViewHolder to store references to the respective view. This solution avoids all the findViewById() method calls in the adapter to find out which views to fill with data.

The code file of the ViewHolder Java class is listed below.

import android.view.View;  
import android.widget.ImageView;  
import android.widget.TextView;  
import androidx.recyclerview.widget.RecyclerView;  
  
public class View_Holder extends RecyclerView.ViewHolder {  
  
    TextView name;  
    ImageView imageView;  
  
    View_Holder(View itemView) {  
        super(itemView);  
        name = (TextView) itemView.findViewById(R.id.name);  
        imageView = (ImageView) itemView.findViewById(R.id.image);  
    }  
} 

This is the ViewHolder file class that extends RecyclerView.ViewHolder class and a constructor with super().

Step 9. Here is the MainActivity.java class file.

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);  
  
        List<Data> data = fill_with_data();  
  
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);  
        RecyclerView_Adapter adapter = new RecyclerView_Adapter(data, getApplication());  
        recyclerView.setAdapter(adapter);  
        recyclerView.setLayoutManager(new LinearLayoutManager(this));  
  
    }  
  
    public List<Data> fill_with_data() {  
  
        List<Data> data = new ArrayList<>();  
        data.add(new Data("C", R.drawable.c));  
        data.add(new Data("C++", R.drawable.cc));  
        data.add(new Data("Java", R.drawable.java));  
        data.add(new Data("Android", R.drawable.android));  
        data.add(new Data("Kotlin", R.drawable.kotlin));  
        data.add(new Data("Html", R.drawable.html));  
        data.add(new Data("CSS", R.drawable.css));  
        data.add(new Data("JavaScript", R.drawable.js));  
        data.add(new Data("SQL", R.drawable.sql));  
        data.add(new Data("SQL Server", R.drawable.sqls));  
        data.add(new Data("Data Structure", R.drawable.data_structure));  
        data.add(new Data("Json", R.drawable.json));  
        data.add(new Data("JSP", R.drawable.jsp));  
        data.add(new Data("Alexa Skills", R.drawable.alexa));  
  
        return data;  
    }  
} 

In this MainActivity.java file, Create an instance of the Recycler View Adapter in the onCreate() method of the MainActivity class, and send this adapter the list of data and background. The method getApplication() will provide the context for an application.

We need sample data. For this example, we generated a method named fill_with_data(). In this method, we provide the text as a string and images to show in the RecyclerView.

Output

Summary

In this article, we learned about RecyclerView in Android Studio with Java programming language, along with an example program.