Android Tutorial on Retrofit Library || Retrofit Android Example

Android Tutorial on Retrofit Library, Fetching data from server is a most common functionality almost in every app, and for which there are several parameters like time taken for fetching data or uploading, connectivity, speed, security and many more.

In this blog we will be looking over a library which will help you fetch data from your api’s much more faster.

Android Tutorial on Retrofit Library

Retrofit Library works with your HTTP API in making it into a java interface making it much flexible and faster for you, which also helps in over all performance of the app.

Fetching data from server is a common task in apps which may be related for analytics, upload / download of images, databases etc.

In this tutorial on Retrofit library we can fetch data from an api and show it in a android recyclerview.

Dependency :

Add Retrofit, recyclerview, gson to your project

Try to add the latest version of dependency’s to your project to avoid abnormal crashes by the usage of deprecated codes.

implementation 'com.squareup.retrofit:retrofit:2.0.0-beta2'
compile 'com.squareup.retrofit:converter-gson:2.0.0-beta2'
compile 'com.android.support:recyclerview-v7:26.1.0'
compile 'com.google.code.gson:gson:2.2.4'

Lets design the row of the listview

listview_row

Add two textviews to the layout for displaying username and age.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/nameTxt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="name"
        android:layout_weight="1"
        android:padding="10dp"/>

    <TextView
        android:id="@+id/ageTxt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="age"
        android:layout_weight="1"
        android:padding="10dp"/>


</LinearLayout>

and then

activity_main :

Add a recyclerview to the layout file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="match_parent"
    tools:context="retrofit.android.com.retrofit.MainActivity">

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

</LinearLayout>

then create a api interface

ApiInterface

In post declare your parameter and also the model class file to parse the response.

public interface ApiInterface {

    @POST("YOUR PARAMETER HERE")
    Call<List<Contact>> getcontacts();

}

ApiClient

Declare your base url here.

public class ApiClient {

    public static final String BASE_URL = "YOUR URL HERE";
    public static Retrofit retrofit = null;

    public static Retrofit getApiClient(){

        if(retrofit==null){

            retrofit = new Retrofit.Builder().baseUrl(BASE_URL)
                       .addConverterFactory(GsonConverterFactory.create())
                       .build();

        }
        return retrofit;
    }

}

Pojo model class for handling data in between api and adapter.For a faster way to generate model classes refer this link using which model class is generated based on the json array specified

Contact

public class Contact {

    private String name;
    private String age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
}

RecyclerAdapter

Recycler adapter is used to improve the app performance by reusing the views multiple times.

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder>{

    private List<Contact> contacts;
    public RecyclerAdapter(List<Contact> contacts)
    {

        this.contacts = contacts;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.listview_row,parent,false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(RecyclerAdapter.MyViewHolder holder, int position) {

        holder.Name.setText(contacts.get(position).getName());
        holder.Age.setText(contacts.get(position).getAge());

    }

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

    public class MyViewHolder extends RecyclerView.ViewHolder{

        TextView Name,Age;

        public MyViewHolder(View itemView) {
            super(itemView);
            Name = (TextView) itemView.findViewById(R.id.nameTxt);
            Age = (TextView) itemView.findViewById(R.id.ageTxt);
        }
    }
}

MainActivity

Now we can fetch data using our api interface

apiInterface = ApiClient.getApiClient().create(ApiInterface.class);

call.enqueue(new Callback<List<Contact>>() {
 @Override
 public void onResponse(Response<List<Contact>> response, Retrofit retrofit) {

 contacts = response.body();
 adapter = new RecyclerAdapter(contacts);
 recyclerView.setAdapter(adapter);

 }

 @Override
 public void onFailure(Throwable t) {

 }
 });

public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerAdapter adapter;
    private List<Contact> contacts;
    private ApiInterface apiInterface;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
       layoutManager = new LinearLayoutManager(this);
       recyclerView.setLayoutManager(layoutManager);
       recyclerView.setHasFixedSize(true);

       apiInterface = ApiClient.getApiClient().create(ApiInterface.class);

        Call<List<Contact>> call = apiInterface.getcontacts();

        call.enqueue(new Callback<List<Contact>>() {
            @Override
            public void onResponse(Response<List<Contact>> response, Retrofit retrofit) {

                contacts = response.body();
                adapter = new RecyclerAdapter(contacts);
                recyclerView.setAdapter(adapter);

            }

            @Override
            public void onFailure(Throwable t) {

            }
        });
    }


}

Manifest

Declare internet permission

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

Output

The screen below depicts Android Tutorial on Retrofit Library usage

Any query’s on the tutorials do let us know in the comment section below or on instagram.