How to Extract Data from JSON Array in Android using Volley Library? - Software Development PDF Download

• Introduction

  In Android development with Volley Library, extracting data from JSON Arrays is a crucial skill. Let's delve into the process of extracting data from a JSON Array and displaying it in an Android application.

• Understanding JSON Array

  JSON Array is a collection of data that contains multiple JSON Objects sharing similar data structures. Identified by opening "[" and closing "]" braces, a JSON Array comprises several JSON Objects, each storing data in key-value pairs.

• Project Overview

  In this project, we will create a simple application featuring CardViews that display various courses available on Geeks for Geeks. The application will be developed using the Java language.

  Below is a sample GIF illustrating the project:

  

• Data Display

  Our Android app will showcase data extracted from the following JSON Array:

  Course Name	Course Image	Course Mode	Course Tracks
  Fork CPP		Online Batch	6 Tracks
  Linux & Shell Scripting Foundation		Online Batch	6 Tracks

• Course Details:
  • Course Name: 11 Weeks Workshop on Data Structures and Algorithms
  • Course Image:
  • Course Mode: Online Batch
  • Course Tracks: 47 Tracks
• Step by Step Implementation:
  • Step 1: Create a New Project
    • To initiate a new project in Android Studio, follow the steps outlined in 'How to Create/Start a New Project in Android Studio'. Ensure that you choose Java as the programming language.
  • Step 2: Add Dependency in build.gradle File
    • Include the following dependency for Volley in your build.gradle file, which will be utilized for retrieving data from the API. Add this dependency in the dependencies section located at app > Gradle Scripts > build.gradle(app). Additionally, the Picasso dependency is used for loading images from URLs.
    • Dependency for Volley: implementation 'com.android.volley:volley:1.1.1'
    • Dependency for Picasso: implementation 'com.squareup.picasso:picasso:2.71828'
    • Upon adding these dependencies, synchronize your project and proceed to the next step concerning the AndroidManifest.xml.
  • Step 3: Grant Internet Permissions in AndroidManifest.xml
    • In the AndroidManifest.xml file located at app > AndroidManifest.xml, insert the provided code snippet to allow internet permissions.

Step 4: Working with the activity_main.xml file

• Navigate to the app > res > layout > activity_main.xml and insert the following code into the file.
• Here is the code snippet for the activity_main.xml file:

RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">

Step 5: Creating a Modal class for storing our data

• Develop a Modal class to store the data efficiently.

Creating a New Java Class: CourseModal

• Begin by navigating to the following path in your project directory: app > java > your app’s package name.

• Right-click on your app’s package name and select New > Java Class.

• Name the new Java class as CourseModal.

• Add the provided code snippet below inside the CourseModal class:

  • Define variables for the course, including courseName, courseimg, courseMode, and courseTracks.

  • Create a constructor to initialize these variables.

  • Implement getter and setter methods for each variable.

• The provided code snippet:

  • public class CourseModal {
  • // variables for our course
  • private String courseName;
  • private String courseimg;
  • private String courseMode;
  • private String courseTracks;
  • // creating constructor for our variables.
  • CourseModal(String courseName, String courseimg, String courseMode, String courseTracks) {
  • this.courseName = courseName;
  • this.courseimg = courseimg;
  • this.courseMode = courseMode;
  • this.courseTracks = courseTracks;
  • }
  • // creating getter and setter methods.
  • String getCourseName() {
  • return courseName;
  • }
  • void setCourseName(String courseName) {
  • this.courseName = courseName;

• Step 6: Creating a layout file for each item of our RecyclerView.

Creating a RecyclerView Item Layout

• Navigate to the app > res > layout.
• Right-click to create a new layout resource file called course_rv_item.
• Add the provided XML code snippet to the file.

XML Code for course_rv_item

Step 7: Creating an Adapter Class

Create an Adapter class to set data for the RecyclerView item.

Creating a New Adapter Class

• Go to the following directory in your project: app > java > your app's package name.
• Right-click on the package name, navigate to New, then select Java class.
• Name the new class as CourseAdapter.
• Add the provided code snippet to the CourseAdapter class.

Code Snippet for CourseAdapter Class

Working with the MainActivity.java File

In this step, you will be working with the MainActivity.java file.

Step 8: Working with the MainActivity.java file

• Go to the MainActivity.java file and refer to the following code.
• Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

MainActivity.java

• Import necessary packages like android.os.Bundle, android.view.View, android.widget.ProgressBar, android.widget.Toast, etc.
• Create variables for UI components like RecyclerView, adapter class, array list, ProgressBar, etc.
• Define the URL from where data will be queried.
• In the onCreate method, initialize variables, retrieve data using getData() method, and build the RecyclerView.
• Implement getData() method to make a JSON array request, parse the response, and populate the courseModalArrayList.
• Implement buildRecyclerView() method to set up the RecyclerView with the adapter.

Explanation with Examples

• RequestQueue: A queue for network requests using Volley library.
• JsonArrayRequest: Request to fetch data in JSON array format.
• JSONObject: Represents a JSON object containing key-value pairs.
• JSONArray: Represents an array in JSON format.
• CourseModal: A model class to hold course details like name, image URL, mode, and tracks.

Implementation and Output

• Initialize the adapter and set the layout manager for the RecyclerView.
• Retrieve data from the URL and populate the RecyclerView with course information.
• Handle API responses and errors using Response and Error Listeners.
• Run the app to see the displayed course information fetched from the provided URL.

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