Network Layer Implementation

Overview

The network layer is responsible for managing communication between the application and remote servers. Retrofit, a type-safe HTTP client for Android, simplifies network requests by providing an easy-to-use API and powerful features such as request serialization, response deserialization, and error handling. This documentation describes the structure and implementation of a network layer using Retrofit in an Android project.

Key Components

• API Interface: Defines endpoints and request methods.
• Retrofit Builder: Configures Retrofit instance.
• Network Models: Represents request and response data structures.
• Network Service: Serves as a single entry point for network operations.

Step-by-Step Implementation

1. Add Dependencies

Include the Retrofit library and additional dependencies in your build.gradle file:

• api ‘'com.squareup.retrofit2:retrofit:2.9.0'
• api 'com.squareup.okhttp3:okhttp:5.0.0-alpha.2'
• api 'com.squareup.okhttp3:logging-interceptor:5.0.0-alpha.2'

2. Define the API Interface

Create an interface that specifies the endpoints, HTTP methods, and request/response types.

public interface ApiInterface {
@POST(EndPoints.LOGIN)
Call<BaseResponse> doLogin(@Body LoginPayload payload);

@GET(EndPoints.Metadata)
Call<BaseResponse> getMetadata(@Query("syncver") String syncVersion); 

@GET(EndPoints.Metadata)
Call<BaseResponse> getMetadata();


 @POST(EndPoints.ENROLLMENT)
 Call<BaseResponse> uploadChildEnrollmentForm(@Body ChildPayload payload);

}

3. Configure Retrofit Instance

Set up a Retrofit instance with a base URL, Gson converter, and optional logging interceptor.

public class RetrofitClient {

    private static final String BASE_URL = "https://..";
    private static Retrofit retrofit;




 public static void setupRestClient(String province) {

   if (!province.equals(Core.getInstance().getAppContext().getString(R.string.default_province))) {

       /*comment for live*/

       HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
       logging.setLevel(HttpLoggingInterceptor.Level.BODY);
       OkHttpClient httpClient =getOkHttpBuilder()
               .addInterceptor(chain -> {
                   Request request = chain.request();
                   Request newRequest;
                   newRequest = request.newBuilder()
                           .addHeader(KEY_HEADER, KEY)
                           .addHeader("AppVersion", getAppVersionName())
                           .build();
                   return chain.proceed(newRequest);
               })
               .addInterceptor(new HeaderInterceptor())
               .connectTimeout(TIMEOUT, TimeUnit.SECONDS).
                       writeTimeout(TIMEOUT, TimeUnit.SECONDS).
                       readTimeout(TIMEOUT, TimeUnit.SECONDS)
               .addInterceptor(logging)

               .build();

       Gson gson = new GsonBuilder()
               .setLenient()
               .create();

       Retrofit retrofit = new Retrofit.Builder().
               baseUrl(Utils.INSTANCE.getUrl(province)).
               addConverterFactory(GsonConverterFactory.create(gson)).
               client(httpClient).
               build();

       restClient = retrofit.create(ApiInterface.class);
   }
}

public static ApiInterface getAuthAdapter() {
   if (restClient == null) {
       Context context = Core.getInstance().getAppContext();
       setupRestClient(DevicePreferences.INSTANCE.getString(context.getString(R.string.pref_province),
               context.getString(R.string.default_province)));
   }
   return restClient;
}

}

4. Implement Network Service

Use the RetrofitInstance to perform network operations.In this Service class we define all our network calls:

public static void doLogin(LoginPayload payload, final OnResponseReceivedListener listener) {
   RestClient.getAuthAdapter().doLogin(payload).enqueue(new Callback<BaseResponse>() {
       @Override
       public void onResponse(@NotNull Call<BaseResponse> call, @NotNull Response<BaseResponse> response) {
           if (response.body() != null) {
               responseCode = response.body().getStatus();
               if (responseCode == ResponseStatus.STATUS_SUCCESS.getId())
                   listener.onSuccessReceived(response.body());
               else if (responseCode == ResponseStatus.STATUS_FAILURE.getId()) {
                   responseError = response.body().getParams().getError();
                   listener.onFailureReceived(responseError != null ? responseError : Utils.INSTANCE.getMessageByResponseCode(responseCode), responseCode);
               } else if (responseCode == ResponseStatus.STATUS_INCORRECT_CREDENTIALS.getId())
                   listener.onFailureReceived(ResponseStatus.values()[responseCode].getMessage(), responseCode);
               else
                   listener.onFailureReceived(Utils.INSTANCE.getMessageByResponseCode(responseCode), responseCode);
           } else
               listener.onFailureReceived(SERVER_SE_KOI_JAWAB_NAHI_AYA, -1);
       }

       @Override
       public void onFailure(@NotNull Call<BaseResponse> call, @NotNull Throwable t) {
           showError(t, listener);
       }
   });
}

public static void getMetadata(final OnResponseReceivedListener listener) {
   RestClient.getAuthAdapter().getMetadata(DevicePreferences.INSTANCE.getString(DevicePreferences.SYNC_VERSION, "0")).enqueue(new Callback<BaseResponse>() {
       @Override
       public void onResponse(@NotNull Call<BaseResponse> call, @NotNull Response<BaseResponse> response) {
           if (response.body() != null) {
               responseCode = response.body().getStatus();
               if (responseCode == ResponseStatus.STATUS_SUCCESS.getId()) {
                   if (response.body().getParams().getSyncVersion() != null)
                       DevicePreferences.INSTANCE.putString(DevicePreferences.SYNC_VERSION, (response.body().getParams().getSyncVersion()));
                   listener.onSuccessReceived(response.body());
               } else
                   listener.onFailureReceived(Utils.INSTANCE.getMessageByResponseCode(responseCode), responseCode);
           } else
               listener.onFailureReceived(SERVER_SE_KOI_JAWAB_NAHI_AYA, -1);
       }

       @Override
       public void onFailure(@NotNull Call<BaseResponse> call, @NotNull Throwable t) {
           showError(t, listener);
       }
   });
}