Easiest Way to Fetch REST API data using Retrofit in Android Jetpack Compose

Let's set up Retrofit, Gson, and Kotlinx Coroutines to fetch a random quote from ZenQuotes API and display it dynamically in Jetpack Compose.

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🔍 1️⃣ Add Dependencies (Retrofit, Gson, Coroutines)

Add these dependencies in your build.gradle.kts (Module-level):

dependencies {
    implementation("com.squareup.retrofit2:retrofit:2.9.0")
    implementation("com.squareup.retrofit2:converter-gson:2.9.0") // Convert JSON to Kotlin objects
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4") // Coroutines
    implementation("com.squareup.okhttp3:logging-interceptor:4.9.3") // Debugging HTTP calls
}

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🏗 2️⃣ Create the Retrofit API Interface

ZenQuotes API provides random quotes in JSON format. Define the API interface:

import retrofit2.http.GET
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.Call

// Step 1: Define Data Model
data class QuoteResponse(val q: String, val a: String) // q = quote, a = author

// Step 2: Define API Interface
interface QuoteApiService {
    @GET("api/random") // Endpoint for random quote
    fun getRandomQuote(): Call<List<QuoteResponse>> // ZenQuotes returns a List
}

// Step 3: Create Retrofit Instance
object RetrofitInstance {
    private const val BASE_URL = "https://zenquotes.io/"

    val apiService: QuoteApiService by lazy {
        Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create()) // Convert JSON
            .build()
            .create(QuoteApiService::class.java)
    }
}

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🚀 3️⃣ Fetch Quote Using Coroutines

Since Retrofit's default method (Call) is synchronous, let's use Coroutines for async operations.

Create a Repository for API Calls:

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext

class QuoteRepository {
    suspend fun fetchRandomQuote(): QuoteResponse? {
        return withContext(Dispatchers.IO) {
            try {
                val response = RetrofitInstance.apiService.getRandomQuote().execute()
                if (response.isSuccessful) response.body()?.get(0) else null // ZenQuotes returns a List
            } catch (e: Exception) {
                null // Handle errors
            }
        }
    }
}

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🌐 4️⃣ Display Quote in Jetpack Compose

Modify your QuoteScreen to display fetched quote dynamically.

import androidx.lifecycle.viewModelScope
import androidx.lifecycle.ViewModel
import kotlinx.coroutines.launch

class QuoteViewModel : ViewModel() {
    private val repository = QuoteRepository()
    var quoteText by mutableStateOf("Tap button for a quote")
    var authorText by mutableStateOf("")

    fun getNewQuote() {
        viewModelScope.launch {
            val quote = repository.fetchRandomQuote()
            if (quote != null) {
                quoteText = "\"${quote.q}\""
                authorText = "- ${quote.a}"
            }
        }
    }
}

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🎨 5️⃣ Connect ViewModel to Your UI (QuoteScreen)

Now, update your Composable to use QuoteViewModel.

@Composable
fun QuoteScreen(viewModel: QuoteViewModel = QuoteViewModel()) {
    Column(
        modifier = Modifier.fillMaxSize().padding(16.dp),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {
        Text(text = viewModel.quoteText, modifier = Modifier.padding(8.dp))
        Text(text = viewModel.authorText, modifier = Modifier.padding(8.dp))
        Button(onClick = { viewModel.getNewQuote() }) {
            Text("Get Quote")
        }
    }
}

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🚀 Final Steps

1. Run the app and click the button to fetch a random quote.
2. ViewModel ensures state survival across recompositions.
3. Coroutines make the API call efficient without blocking UI.

Now you have a fully functional random quote generator integrated into Jetpack Compose! 🚀🔥