Koin Tutorial – Setting up Dependency Injection Layer and Application Class in Android (Kotlin MVVM)

In this **Koin Tutorial**, we’re going back to the foundations — setting up the **Dependency Injection (DI) layer** and configuring the **Application class** in an Android project using Kotlin. Koin is a lightweight and pragmatic DI framework designed specifically for Kotlin developers, making it an excellent choice for Android development.

This tutorial is perfect for those working with **MVVM architecture** or simply looking to introduce clean dependency management into their Android app. We’ll walk through every step of integrating Koin into your project — from adding dependencies to setting up your first Koin module and initializing the framework in the Application class.

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### 🚀 What You'll Learn:

✅ How to add Koin to your Android project
✅ How to create your DI module(s)
✅ How to structure the DI layer for scalability
✅ How to initialize Koin in the Application class
✅ Best practices for managing dependencies with Koin

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### 🛠️ Prerequisites:

- Android Studio setup with a Kotlin project
- Basic understanding of Android components
- Familiarity with MVVM (Model-View-ViewModel) is a plus

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### 🧱 Step-by-Step Overview:

```kotlin
```

2. **Create Your DI Module(s):**
Organize your dependencies in a clean, scalable way:
```kotlin
val appModule = module {
single { NetworkClient() }
single { UserRepository(get()) }
viewModel { MainViewModel(get()) }
}
```

3. **Initialize Koin in Your Application Class:**
```kotlin
class MyApp : Application() {
override fun onCreate() {
startKoin {
modules(appModule)
}
}
}
```

4. **Declare Application Class in Manifest:**
```xml
application
android:name=".MyApp"
...
/application
```

5. **Use Injected Dependencies Anywhere in the App:**
```kotlin
class MainActivity : AppCompatActivity() {
private val viewModel: MainViewModel by viewModel()
...
}
```

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### 📌 Best Practices:

- Split your DI modules by feature (e.g., `networkModule`, `repositoryModule`, `viewModelModule`) for large projects.
- Use `single` for shared instances and `factory` for new instances on each injection.
- Keep initialization logic minimal in the Application class — just start Koin and load modules.

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Get started with **clean architecture** and scalable code using Koin!

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