Data-Driven Development in Android Kotlin: A Comprehensive Guide Using Clean Architecture, Koin, Ktor, and Use Cases
Making Android Apps Smarter and Easier to Maintain with Clean Architecture and Powerful Tools
Hey there, devs! How's it going? I'm your app sensei, and today we're diving into DDD. So, data-driven development is all about designing and building your app based on the data it handles and how it flows through your system. When you combine this approach with Clean Architecture, Koin for dependency injection, Ktor for API calls, and Use Cases for business logic, you can create Android apps that are easy to maintain, scale, and test.
In this blog post, I'll walk you through how to implement data-driven development in an Android Kotlin app using these tools.
Why Data-Driven Development?
Data-driven development helps ensure that your application remains:
Scalable: Easily handles more data as your app grows.
Maintainable: Makes updates and bug fixes easier.
Testable: With a clear separation of data and UI logic, unit testing becomes much easier.
Adaptable: You can easily manage changes in business logic by adjusting how data is handled and processed.
Clean Architecture Overview
Clean Architecture, introduced by Robert C. Martin, breaks your code into clear layers that keep different parts of your app separate. This approach makes your code easier to manage and test. The key layers include:
Domain Layer: Core business logic and rules, independent of any external framework or UI.
Presentation Layer: Converts data from the use cases and entities to a format convenient for the outer layers, such as the UI.
Data Layer: Manages external details like databases, network communication, and device-specific APIs.
Setting Up the Project
1. Project Structure
We’ll set up a modular project structure that aligns with Clean Architecture principles:
com.example.app
│
├── domain (Domain Layer)
│ ├── model (Entities)
│ ├── repository (Repository Interfaces)
│ └── usecase (Use Cases)
│
├── data (Data Layer)
│ ├── repository (Repository Implementations)
│ ├── remote (Ktor API Call Handling)
│ └── di (Koin Modules)
│
└── presentation (Presentation Layer)
├── viewmodel (ViewModels)
└── ui (UI Components)
2. Adding Dependencies
Add the necessary dependencies to your build.gradle file:
dependencies {
// Koin
implementation "io.insert-koin:koin-core:3.5.0"
implementation "io.insert-koin:koin-android:3.5.0"
// Ktor
implementation "io.ktor:ktor-client-core:2.4.0"
implementation "io.ktor:ktor-client-cio:2.4.0"
implementation "io.ktor:ktor-client-serialization:2.4.0"
// Coroutines
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3"
// AndroidX
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.1"
}
Domain Layer: Core Business Logic and Use Cases
The domain layer is where all the core business logic lives. It includes entities, repository interfaces, and use cases. This layer stands on its own, without relying on any external frameworks or the user interface.
1. Entity
Define a simple entity class representing the data model. For example, if you're building a weather app:
package com.example.app.domain.model
data class Weather(
val temperature: Double,
val description: String,
val city: String
)
2. Repository Interface
The repository interface defines the contract for data operations, independent of the data source:
package com.example.app.domain.repository
import com.example.app.domain.model.Weather
interface WeatherRepository {
suspend fun getWeather(city: String): Weather
}
3. Use Case
Use cases coordinate the flow of data to and from the entities and the repository, acting as an intermediary that applies business logic.
package com.example.app.domain.usecase
import com.example.app.domain.model.Weather
import com.example.app.domain.repository.WeatherRepository
class GetWeatherUseCase(private val weatherRepository: WeatherRepository) {
suspend operator fun invoke(city: String): Weather {
// Add any business logic here
return weatherRepository.getWeather(city)
}
}
Data Layer: Repository Implementations and API Integration
The data layer takes care of implementing the repository interfaces and handling external data sources, such as APIs.
1. Setting Up Ktor for API Calling
Configure the Ktor client, which will be used to make API calls:
package com.example.app.data.remote
import io.ktor.client.*
import io.ktor.client.call.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import io.ktor.client.features.json.*
import io.ktor.client.features.json.serializer.*
import io.ktor.client.features.logging.*
import io.ktor.http.*
object KtorClient {
val client = HttpClient {
install(JsonFeature) {
serializer = KotlinxSerializer()
}
install(Logging) {
level = LogLevel.BODY
}
}
}
2. Repository Implementation
Implement the WeatherRepository interface using Ktor to fetch data from an API:
package com.example.app.data.repository
import com.example.app.domain.model.Weather
import com.example.app.domain.repository.WeatherRepository
import com.example.app.data.remote.KtorClient
import io.ktor.client.request.*
class WeatherRepositoryImpl : WeatherRepository {
override suspend fun getWeather(city: String): Weather {
val response: WeatherResponse = KtorClient.client.get("https://api.weather.com/v3/wx/conditions/current") {
parameter("city", city)
parameter("apiKey", "your_api_key_here")
}
return Weather(
temperature = response.temperature,
description = response.weatherDescription,
city = city
)
}
}
data class WeatherResponse(
val temperature: Double,
val weatherDescription: String
)
3. Koin Modules
Use Koin to provide dependencies, including the repository and use case:
package com.example.app.data.di
import com.example.app.data.repository.WeatherRepositoryImpl
import com.example.app.domain.repository.WeatherRepository
import com.example.app.domain.usecase.GetWeatherUseCase
import org.koin.dsl.module
val appModule = module {
single<WeatherRepository> { WeatherRepositoryImpl() }
factory { GetWeatherUseCase(get()) }
}
Presentation Layer: ViewModel and UI Components
The presentation layer is where the ViewModel and UI components come into play, using the data provided by the domain layer.
1. ViewModel
Create a ViewModel that interacts with the GetWeatherUseCase to fetch and expose weather data to the UI:
package com.example.app.presentation.viewmodel
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.example.app.domain.model.Weather
import com.example.app.domain.usecase.GetWeatherUseCase
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.launch
class WeatherViewModel(private val getWeatherUseCase: GetWeatherUseCase) : ViewModel() {
private val _weather = MutableStateFlow<Weather?>(null)
val weather: StateFlow<Weather?> get() = _weather
fun fetchWeather(city: String) {
viewModelScope.launch {
_weather.value = getWeatherUseCase(city)
}
}
}
2. UI Components
Finally, create a simple UI to display the weather data:
package com.example.app.presentation.ui
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.lifecycle.viewmodel.compose.viewModel
import com.example.app.presentation.viewmodel.WeatherViewModel
import org.koin.androidx.viewmodel.ext.android.viewModel
class WeatherActivity : AppCompatActivity() {
private val weatherViewModel: WeatherViewModel by viewModel()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
WeatherScreen(weatherViewModel)
}
}
}
@Composable
fun WeatherScreen(viewModel: WeatherViewModel) {
var city by remember { mutableStateOf("") }
Column(
modifier = Modifier.fillMaxSize().padding(16.dp)
) {
TextField(
value = city,
onValueChange = { city = it },
label = { Text("City") }
)
Spacer(modifier = Modifier.height(8.dp))
Button(onClick = { viewModel.fetchWeather(city) }) {
Text("Get Weather")
}
Spacer(modifier = Modifier.height(16.dp))
val weather by viewModel.weather.collectAsState()
weather?.let {
Text("Temperature: ${it.temperature}°C")
Text("Description: ${it.description}")
Text("City: ${it.city}")
}
}
}
In this article, we've taken a look at how to use data-driven development in an Android Kotlin app with Clean Architecture. We used Koin for dependency injection, Ktor for making API calls, and Use Cases to handle business logic. This method helps keep your code clean, easy to maintain, and scalable, making it simpler to manage and improve as time goes on.
Use Cases are super important for keeping the business logic separate from other parts of your app. This ensures your app stays modular and can easily handle future updates. By sticking to these guidelines, you can create strong and testable Android apps that smoothly adjust to new business needs.
This approach gives you a solid starting point for building data-driven Android apps, offering a clear path to a well-structured and easy-to-maintain codebase.
Alright, devs, it's time to wrap up this article! I hope you now have a better understanding of data-driven development. If you need any help, feel free to reach out. See you in the next article, devs!
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