Introduction to Retrofit 2 in android - Software Development PDF Download

Introduction to Retrofit 2 in Android | Set 1

Overview

• Retrofit 2 is a type-safe REST client developed by Square for Android and Java.
• It simplifies the process of expanding RESTful web services.
• Retrofit 2 utilizes OkHttp as the networking layer.
• Automatically serializes JSON responses using a POJO (Plain Old Java Object) defined in advance for the JSON structure.
• To serialize JSON, a converter is needed to convert it to Gson first.
• While Retrofit simplifies the process by directly returning objects, it lacks support for loading images from the server.
• Picasso can be used to address this limitation.

Implementation

Step 1: Adding Retrofit Dependency

• Open the app/build.gradle file in your Android project.
• Add the necessary dependency inside the dependencies block.

Step 2: Adding Internet Permission

• Open the manifest.xml file.
• Include the Internet permission.

Step 3: Creating a Model Class

• For data retrieval using Retrofit 2, a model class is required.
• The model class structure should match the JSON data format.

Example JSON Data Structure

• "current_page": 1
• "data": [
  • "id": 1, "source": "http://mhrd.gov.in/sites/upload_files/mhrd/files/upload_document/NSISGE-Scheme-Copy.pdf", "name": "National Scheme of Incentive to Girls for Secondary Education (NSIGSE)", "sector": "Education", "government": "Central", "eligible_beneficiaries": "Individual", "requirements": "i. Girls who pass class VIII examination and enroll for class IX in State/UT Government, Government-aided, or local body schools..."

Model Class for Scheme

• The Scheme class is a model class that implements the Parcelable interface in Android development.
• It contains various fields such as source, state URL, sector URL, ID, name, sector, government, eligible beneficiaries, maximum income, social category, religion, requirements, benefits, how to apply, gender, minimum age, maximum age, qualification, marital status, BPL status, and disability.
• Getter and setter methods are provided for each field to ensure data encapsulation and access control.
• The class also includes methods for describing contents and writing to parcel, essential for Parcelable implementation.

Pagination Handling in JSON

• The JSON data retrieved is paginated, with each set containing 10 entries.
• Pagination is a technique used to break down large datasets into smaller, more manageable parts for easier retrieval and display.
• By implementing pagination, users can navigate through different pages of data rather than loading everything at once, enhancing user experience and reducing load times.
• It helps in organizing and presenting data systematically, especially in situations where displaying all data simultaneously is impractical or overwhelming.

Code for Pagination

• Import necessary libraries for pagination handling in Android.
• Create a class named Page that implements the Parcelable interface.
• Define attributes for the Page class such as currentPage, data, from, lastPage, nextPageUrl, path, perPage, prevPageUrl, to, and total.
• Implement constructors and getter/setter methods for these attributes.
• Override necessary methods like describeContents and writeToParcel for Parcelable implementation.
• Refer to the provided code snippet for a detailed implementation.

Adapter and API Service Provider Setup

• Create an Adapter class to bind data to views for display.
• Implement methods like onCreateViewHolder and onBindViewHolder in the Adapter class.
• Set up an API service provider using Retrofit library for handling network requests.
• Define API endpoints and associated methods for data retrieval and manipulation.

Data Display and Usage

• Utilize the Adapter to populate data in appropriate views like RecyclerView.
• Make API calls using the Retrofit service provider to fetch data from a server.
• Handle pagination logic to load and display data in chunks.
• Ensure smooth user interaction and seamless data loading for a better user experience.

Now that we have set up the model class for data handling and pagination class for managing data display, the next steps involve creating an Adapter and API service provider to showcase our data. These aspects will be covered in the upcoming parts of this tutorial.

Reference:

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