Retrofit2 Setup

Add below files in Gradle
compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
compile 'com.squareup.okhttp3:logging-interceptor:3.6.0'

Create Api Client

public class ApiClient {
    private static Retrofit retrofit = null;
    private static final String CACHE_CONTROL = "Cache-Control";
    public static Retrofit getClient() {
        if (retrofit == null) {
            HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
            logging.setLevel(HttpLoggingInterceptor.Level.BODY);
            OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
            httpClient.addInterceptor(logging);
            httpClient.readTimeout(120, TimeUnit.SECONDS);
            httpClient.connectTimeout(120, TimeUnit.SECONDS);

            Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ").create();
            retrofit = new Retrofit.Builder()
                    .baseUrl(Constants.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .client(httpClient.build())
                    .build();
        }
        return retrofit;
    }
}

Create End Point

public interface Endpoint{

    @FormUrlEncoded
    @POST("api/auth/login")
    Call<LoginBeann> loginCall(@Field("email") String email, @Field("password") String password, @Field("lang")String language);
}

LoginBean Class--
public class LoginBeann{
    @SerializedName("status")
    @Expose
    private String status;
    @SerializedName("message")
    @Expose
    private String message;
    @SerializedName("data")
    @Expose
    private LoginBean data;

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public LoginBean getData() {
        return data;
    }

    public void setData(LoginBean data) {
        this.data = data;
    }
}

After Above setup. We can call the Login API

Endpoint endpoint = ApiClient.getClient().create(Endpoint.class);
private Call<LoginBeann> loginCall;


loginCall = endpoint.loginCall(email,password,language);
              loginCall.enqueue(new Callback<LoginBeann>() {
                @Override
                public void onResponse(Call<LoginBeann> call, Response<LoginBeann> response) {
                    if (dialog.isShowing()) {
                        dialog.dismiss();
                    }
                    if (response.isSuccessful() && response.body().getData() != null && response.body().getStatus().equals("success")) {
                       
                    }else if (response.body() !=null && response.body().getStatus().equals("fail")) {
                        toastCall(response.body().getMessage());
                    } else {
                        toastCall(response.body().getMessage());

                    }
                }
                @Override
                public void onFailure(Call<LoginBeann> call, Throwable t) {
                    if (dialog.isShowing()) {
                        dialog.dismiss();
                    }
                    if (call.isCanceled())
                        return;
                    new PrintLog(activity).display("Login Error",t+"");
                }
            });