Android – JSON Parsing Using Retrofit Library with Jetpack Compose

JSON is a format with the help of which we can exchange the data from the server within our application or a website. For accessing this data from the server within android applications. There are several libraries that are available such as Volley and Retrofit. In this article, we will take a look at JSON Parsing in Android applications using Jetpack Compose. 

Step by Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. While choosing the template, select Empty Compose Activity. If you do not find this template, try upgrading the Android Studio to the latest version. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.

Step 2: Adding dependency for using Retrofit

Navigate to app > Gradle Scripts > build.gradle file and add the below dependency to it. Comments are added to the code.

// below dependency for using retrofit.
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'

// below dependency for using picasso image loading library
implementation 'com.squareup.picasso:picasso:2.71828'

After adding this dependency simply sync your project to install it.

Step 3: Adding a new color in the Color.kt file

Navigate to app > java > your app’s package name > ui.theme > Color.kt file and add the below code to it.   

Kotlin

package com.example.newcanaryproject.ui.theme

import androidx.compose.ui.graphics.Color

val Purple200 = Color(0xFF0F9D58)
val Purple500 = Color(0xFF0F9D58)
val Purple700 = Color(0xFF3700B3)
val Teal200 = Color(0xFF03DAC5)

// on below line we are adding different colors.
val greenColor = Color(0xFF0F9D58)

Step 4: Adding permissions to the internet in the AndroidManifest.xml file

Navigate to the app > AndroidManifest.xml and add the below code to it.  

XML

<!--permissions for INTERNET-->
<uses-permission android:name="android.permission.INTERNET"/>

Step 5: Creating a Modal class

Navigate to app > java > your app’s package name > Right-click on it > New > Kotlin class and specify the name of the class as CourseDataModal and add the below code to it. Comments are added in the code to get to know in detail. 

Kotlin

package com.example.newcanaryproject

data class CourseDataModal(
    // on below line creating variables for our modal class
    // make sure that variable name should be same to
    // that of key which is used in json response.
    var courseName: String,
    var courseimg: String,
    var courseDesc: String,
    var Prerequisites: String,
    var courseLink: String
)

Step 6: Creating an Interface

Navigate to app > java > your app’s package name > Right-click on it > New > Kotlin class and select interface in it and then specify the name as RetrofitAPI. Add the below code to it. Comments are added in the code to get to know in detail. 

Kotlin

package com.example.newcanaryproject

import retrofit2.Call
import retrofit2.http.GET

interface RetrofitAPI {
    // as we are making get request
    // so we are displaying GET as annotation.
    // and inside we are passing
    // last parameter for our url.
    @GET("8RFY")
    fun  // as we are calling data from array
    // so we are calling it with json object
    // and naming that method as getCourse();
            getCourse(): Call<CourseDataModal?>?
}

Step 7: Working with the MainActivity.kt file

Navigate to app>java>your app’s package name>MainActivity.kt file and add the below code to it. Comments are added in the code to get to know in detail. 

Kotlin

package com.example.newcanaryproject

import android.content.Context
import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.*
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.res.colorResource
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.*
import coil.compose.rememberAsyncImagePainter
import com.example.newcanaryproject.ui.theme.*
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

class MainActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            NewCanaryProjectTheme {
                // on below line we are specifying background color for our application
                Surface(
                    // on below line we are specifying modifier and color for our app
                    modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background
                ) {

                    // on below line we are specifying theme as scaffold.
                    Scaffold(

                        // in scaffold we are specifying top bar.
                        topBar = {

                            // inside top bar we are specifying background color.
                            TopAppBar(backgroundColor = greenColor,

                                // along with that we are specifying title
                                // for our top bar.
                                title = {

                                    // in the top bar we are specifying tile as a text
                                    Text(

                                        // on below line we are specifying
                                        // text to display in top app bar.
                                        text = "JSON Parsing in Android",

                                        // on below line we are specifying
                                        // modifier to fill max width.
                                        modifier = Modifier.fillMaxWidth(),

                                        // on below line we are specifying
                                        // text alignment.
                                        textAlign = TextAlign.Center,

                                        // on below line we are specifying
                                        // color for our text.
                                        color = Color.White
                                    )
                                })
                        }) {
                        // on below line we are calling pop window
                        // dialog method to display ui.
                        volleyJSONParsing()
                    }
                }
            }
        }
    }
}

// on below line we are creating a
// pop up window dialog method
@Composable
fun volleyJSONParsing() {
    val ctx = LocalContext.current
    // on below line we are creating variables.
    val courseName = remember {
        mutableStateOf("")
    }
    val courseRequisites = remember {
        mutableStateOf("")
    }
    val courseImg = remember {
        mutableStateOf("")
    }
    val courseDesc = remember {
        mutableStateOf("")
    }
    val courseLink = remember {
        mutableStateOf("")
    }
    val progress = remember {
        mutableStateOf(true)
    }

    jsonParsing(ctx, courseName, courseRequisites, courseImg, courseDesc, courseLink, progress)

    // on the below line we are creating a column.
    Column(
        // in this column we are specifying
        // modifier to add padding and fill
        // max size
        modifier = Modifier
            .fillMaxSize()
            .padding(horizontal = 20.dp),

        // on below line we are adding horizontal alignment
        // and vertical arrangement
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Top
    ) {

        // on below line we are creating a column.
        if (progress.value) {
            Column(
                // in this column we are specifying
                // modifier to add padding and fill
                // max size
                modifier = Modifier
                    .fillMaxSize()
                    .padding(horizontal = 20.dp),

                // on below line we are adding horizontal alignment
                // and vertical arrangement
                horizontalAlignment = Alignment.CenterHorizontally,
                verticalArrangement = Arrangement.Center
            ) {
                // below line is use to display a circular progress bar.
                CircularProgressIndicator(
                    // below line is use to add padding to our progress bar.
                    modifier = Modifier.padding(16.dp),

                    // below line is use to add color to our progress bar.
                    color = colorResource(id = R.color.purple_200),

                    // below line is use to add stroke width to our progress bar.
                    strokeWidth = Dp(value = 4F)
                )
            }
        }

        // on the below line we are adding a spacer.
        Spacer(modifier = Modifier.height(4.dp))

        // on below line we are adding image for our image view.
        Image(
            // on below line we are adding the image url
            // from which we will  be loading our image.
            painter = rememberAsyncImagePainter(courseImg.value),

            // on below line we are adding content
            // description for our image.
            contentDescription = "gfg image",

            // on below line we are adding modifier for our
            // image as wrap content for height and width.
            modifier = Modifier
                .wrapContentSize()
                .wrapContentHeight()
                .fillMaxWidth()
                .padding(4.dp),
            alignment = Alignment.Center
        )

        // on the below line we are adding a spacer.
        Spacer(modifier = Modifier.height(10.dp))

        // on below line we are creating
        // text for course name.
        Text(
            text = courseName.value,
            modifier = Modifier.fillMaxWidth(),
            color = Color.Black,
            fontSize = 20.sp,
            fontFamily = FontFamily.Default,
            fontWeight = FontWeight.Bold, textAlign = TextAlign.Center
        )

        // on below line we are adding spacer
        Spacer(modifier = Modifier.height(20.dp))

        // on below line we are adding
        // text for course prerequisites
        Text(
            text = courseRequisites.value,
            modifier = Modifier.fillMaxWidth(),
            color = Color.Black,
            fontSize = 16.sp,
            fontFamily = FontFamily.Default,
            fontWeight = FontWeight.Normal, textAlign = TextAlign.Center
        )

        // on below line we are adding spacer
        Spacer(modifier = Modifier.height(30.dp))

        // on below line we are creating a
        // text for our description.
        Text(
            text = courseDesc.value,
            modifier = Modifier.fillMaxWidth(),
            color = Color.Black,
            fontSize = 15.sp,
            fontFamily = FontFamily.Default,
            fontWeight = FontWeight.Normal, textAlign = TextAlign.Start
        )

        // on the below line we are creating a column.
        Column(
            // in this column we are specifying
            // modifier to add padding and fill
            // max size
            modifier = Modifier
                .fillMaxSize(),
            // on below line we are adding horizontal alignment
            // and vertical arrangement
            horizontalAlignment = Alignment.CenterHorizontally,
            verticalArrangement = Arrangement.Bottom
        ) {
            // on below line we are creating a button
            Button(
                onClick = {
                    // on below line we are opening
                    // a intent to view the url.
                    val i = Intent(Intent.ACTION_VIEW)
                    i.setData(Uri.parse(courseLink.value))
                    ctx.startActivity(i)
                },
                // on below line we are
                // adding modifier for our button.
                modifier = Modifier
                    .fillMaxWidth()
                    .padding(3.dp)
                    .align(Alignment.CenterHorizontally)
                    .fillMaxWidth()
            ) {
                // on below line we are setting text as visit course
                Text(text = "Visit Course", color = Color.White)
            }
        }

    }
}

fun jsonParsing(
    ctx: Context,
    name: MutableState<String>,
    requisites: MutableState<String>,
    Img: MutableState<String>,
    Desc: MutableState<String>,
    Link: MutableState<String>,
    progress: MutableState<Boolean>,
) {

    // on below line we are creating a retrofit
    // builder and passing our base url
    // on below line we are creating a retrofit
    // builder and passing our base url
    val retrofit = Retrofit.Builder()
        .baseUrl("https://jsonkeeper.com/b/")

        // on below line we are calling add Converter
        // factory as GSON converter factory.
        // at last we are building our retrofit builder.
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    // below line is to create an instance for our retrofit api class.
    // below line is to create an instance for our retrofit api class.
    val retrofitAPI = retrofit.create(RetrofitAPI::class.java)

    val call: Call<CourseDataModal?>? = retrofitAPI.getCourse()

    // on below line we are making a call.
    call!!.enqueue(object : Callback<CourseDataModal?> {
        override fun onResponse(
            call: Call<CourseDataModal?>?,
            response: Response<CourseDataModal?>
        ) {
            if (response.isSuccessful()) {
                // inside the on response method.
                // on below line we are getting data from our response
                // and setting it in variables.
                val courseName: String = response.body()!!.courseName
                val courseLink: String = response.body()!!.courseLink
                val courseImg: String = response.body()!!.courseimg
                val courseDesc: String = response.body()!!.courseDesc
                val coursePreq: String = response.body()!!.Prerequisites

                progress.value = !progress.value
                // on below line we are setting
                // our data to our variables
                name.value = courseName
                Link.value = courseLink
                Img.value = courseImg
                Desc.value = courseDesc
                requisites.value = coursePreq

            }
        }

        override fun onFailure(call: Call<CourseDataModal?>?, t: Throwable?) {
            // displaying an error message in toast
            Toast.makeText(ctx, "Fail to get the data..", Toast.LENGTH_SHORT)
                .show()
        }
    })
}

Now run your application to see the output of it. 

Output: