MainActivity.java

package ghozay19.com.retrofitday1;

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

import java.util.ArrayList;
import java.util.List;

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

public class MainActivity extends AppCompatActivity {
    List<ProvinsiModel> provinsiList = new ArrayList<>();
    RecyclerView recyclerView;

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

        recyclerView = (RecyclerView) findViewById(R.id.Rv_Nama_Provinsi);
        LinearLayoutManager llm = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(llm);

        //membuat objek retrofit
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://dev.farizdotid.com/api/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();

// mencetak pelayanan atau service
        ClientServices service = retrofit.create(ClientServices.class);

//membuat objek request
        Call<ProvinsiIndonesiaModel> request = service.getDataProvinsiIndonesia();

//mengirimkan request
        request.enqueue(new Callback<ProvinsiIndonesiaModel>() {
            @Override
            public void onResponse(Call<ProvinsiIndonesiaModel> call,
                                   Response<ProvinsiIndonesiaModel> response) {
                provinsiList = response.body().getSemuaprovinsi();
                ProvinsiAdapter adapter = new
                        ProvinsiAdapter(MainActivity.this,
                        provinsiList);
                recyclerView.setAdapter(adapter);
            }

            @Override
            public void onFailure(Call<ProvinsiIndonesiaModel> call,
                                  Throwable t) {
                Toast.makeText(MainActivity.this,
                        "Connection Failed",
                        Toast.LENGTH_LONG).show();
            }
        });
    }
}