In our previous tutorials we learned to implement a simple RecyclerView and loading image in RecyclerView using Picasso. In this tutorial we are going to learn how to parse JSON data from URL and display it in RecyclerView using Retrofit. We parse the JSON response from the URL http://api.learn2crack.com/android/jsonandroid.
Take a look at my previous RecyclerView tutorials for reference.

Retrofit is a HTTP client library by Square Inc. It makes networking easier and also easy to implement.

Here I have created a Android Studio project with package com.learn2crack.recyclerjsonparsing also Activity as MainActivity and layout as activity_main.

You can download the complete project as zip or fork from our Github repository.

The dependency for Retrofit is

compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'

Then we need to add Retrofit GSON converter library. This takes care of Serialization (Converts Java objects to JSON and vice versa).

compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'

The other dependencies we require,

compile 'com.android.support:appcompat-v7:23.2.0'
compile 'com.android.support:recyclerview-v7:23.2.0'
compile 'com.android.support:cardview-v7:23.2.0'

The complete build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        applicationId "com.learn2crack.recyclerjsonparsing"
        minSdkVersion 21
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.2.0'
    compile 'com.android.support:recyclerview-v7:23.2.0'
    compile 'com.android.support:cardview-v7:23.2.0'
    compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'
    compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'
}

We need to add Internet permission in our AndroidManifest.xml

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

Our main layout has only one RecyclerView widget in LinearLayout.

<LinearLayout 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="com.learn2crack.recyclerjsonparsing.MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/card_recycler_view"
        android:scrollbars="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

The next layout is for RecylerView list item. It has three TextView widgets to display Android version name, version number and API level.

<android.support.v7.widget.CardView
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="5dp"
    android:layout_marginLeft="5dp"
    android:layout_marginRight="5dp"
    card_view:cardCornerRadius="5dp">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="10dp"
        android:orientation="vertical">
        <TextView
            android:id="@+id/tv_name"
            android:layout_marginTop="10dp"
            android:layout_marginBottom="10dp"
            android:textSize="18sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textStyle="bold" />
        <TextView
            android:id="@+id/tv_version"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
        <TextView
            android:id="@+id/tv_api_level"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />

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

Now we create AndroidVersion model class to store Android version name, version number and API level. We obtain a array of JSON objects similar to,

{
"ver": "1.5",
"name": "Cupcake",
"api": "API level 3"
}

This AndroidVersion model class stores the JSON object. The variable declaration name should be same as JSON object name. In the above JSON response, for JSON object name “ver” the variable name should be defined as “ver” ,

private String ver;

The Retrofit GSON converter takes care of converting the JSON objects and store it in our model class.Then generate getter methods.

package com.learn2crack.recyclerjsonparsing;

public class AndroidVersion {
    private String ver;
    private String name;
    private String api;

    public String getVer() {
        return ver;
    }

    public String getName() {
        return name;
    }

    public String getApi() {
        return api;
    }
}

Then we need to create a JSONResponse model. The JSON response has a only JSON object “android” with child JSON array. This child JSON array can be stored in AndroidVersion model class. In our JSONResponse model class create a AndroidVersion array variable named “android” and generate getter.

package com.learn2crack.recyclerjsonparsing;

public class JSONResponse {
    private AndroidVersion[] android;

    public AndroidVersion[] getAndroid() {
        return android;
    }
}

We need to create a Interface and define the Request endpoints. Here we use GET request to obtain JSON data. The endpoint is defined using @GET annotation. Our request URL is http://api.learn2crack.com/android/jsonandroid, where http://api.learn2crack.com is base url and android/jsonandroid is endpoint.

For our request method getJSON() the JSONResponse object is wrapped in Call object. By using Call, the request is made Asynchronous so you need not worry about UI blocking or AsyncTask. The JSON response received after making the request it is stored in JSONResponse object.

package com.learn2crack.recyclerjsonparsing;

import retrofit2.Call;
import retrofit2.http.GET;

public interface RequestInterface {

    @GET("android/jsonandroid")
    Call<JSONResponse> getJSON();
}

We are using the adapter similar to the one we used in our previous projects. We pass Androidversion model class as ArrayList in constructor. We obtain the Android version name, version number, API level from the AndroidVersion object using the getter methods and set it to TextView widgets.

package com.learn2crack.recyclerjsonparsing;

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 DataAdapter extends RecyclerView.Adapter<DataAdapter.ViewHolder> {
    private ArrayList<AndroidVersion> android;

    public DataAdapter(ArrayList<AndroidVersion> android) {
        this.android = android;
    }

    @Override
    public DataAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_row, viewGroup, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(DataAdapter.ViewHolder viewHolder, int i) {

        viewHolder.tv_name.setText(android.get(i).getName());
        viewHolder.tv_version.setText(android.get(i).getVer());
        viewHolder.tv_api_level.setText(android.get(i).getApi());
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder{
        private TextView tv_name,tv_version,tv_api_level;
        public ViewHolder(View view) {
            super(view);

            tv_name = (TextView)view.findViewById(R.id.tv_name);
            tv_version = (TextView)view.findViewById(R.id.tv_version);
            tv_api_level = (TextView)view.findViewById(R.id.tv_api_level);

        }
    }

}

The views are initialized in initViews() method. In the loadJSON() method we initialize Retrofit and carry out network operations. The Retrofit is defined using,

Retrofit retrofit = new Retrofit.Builder()
.baseUrl(http://api.learn2crack.com)
.addConverterFactory(GsonConverterFactory.create())
.build();

RequestInterface object is created using

RequestInterface request = retrofit.create(RequestInterface.class);

To carry out a asyncronous request Call object should be created from RequestInterface object by calling getJSON() method.

Call<JSONResponse> call = request.getJSON();

The Asyncronous request is executed by calling enqueue() method on the call object. If the request is success and response is received onResponse() callback method is executed. The JSONResponse object is obtained by calling body() method on the Response object. From the JSONResponse object we obtain the AndroidVersion array object. We convert the AndroidVersion array object to ArrayList. Finally a new DataAdapter object is created and set to RecyclerView using setAdapter() method.

If the request fails onFailure() is executed.

package com.learn2crack.recyclerjsonparsing;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import java.util.ArrayList;
import java.util.Arrays;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private ArrayList<AndroidVersion> data;
    private DataAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initViews();
    }
    private void initViews(){
        recyclerView = (RecyclerView)findViewById(R.id.card_recycler_view);
        recyclerView.setHasFixedSize(true);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);
        loadJSON();
    }
    private void loadJSON(){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(http://api.learn2crack.com)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
        RequestInterface request = retrofit.create(RequestInterface.class);
        Call<JSONResponse> call = request.getJSON();
        call.enqueue(new Callback<JSONResponse>() {
            @Override
            public void onResponse(Call<JSONResponse> call, Response<JSONResponse> response) {

                JSONResponse jsonResponse = response.body();
                data = new ArrayList<>(Arrays.asList(jsonResponse.getAndroid()));
                adapter = new DataAdapter(data);
                recyclerView.setAdapter(adapter);
            }

            @Override
            public void onFailure(Call<JSONResponse> call, Throwable t) {
                Log.d("Error",t.getMessage());
            }
        });
    }
}

Enjoy Coding 🙂