Android MVVM Architecture with Retrofit — The Right Way in 2026

Why MVVM Is the Standard in 2026

MVVM is what Google recommends and what every serious Android codebase uses. Going into an interview in 2026 talking about putting API calls in your Activity will cost you the job. This guide builds the pattern from scratch so you understand it, not just copy it.

The Three Layers

• View (Activity/Fragment) — only observes state, never fetches data
• ViewModel — holds UI state, calls Repository, survives config changes
• Repository — single source of truth, handles network and cache decisions

Setting Up Retrofit

object ApiClient {
    private const val BASE_URL = "https://api.example.com/"
    private val retrofit = Retrofit.Builder()
        .baseUrl(BASE_URL)
        .addConverterFactory(GsonConverterFactory.create())
        .build()
    val service: ApiService = retrofit.create(ApiService::class.java)
}

The Repository

class UserRepository {
    private val api = ApiClient.service
    suspend fun getUser(id: Int): Result<UserResponse> {
        return try {
            val response = api.getUser(id)
            if (response.isSuccessful) Result.success(response.body()!!)
            else Result.failure(Exception("Error: ${response.code()}"))
        } catch (e: Exception) { Result.failure(e) }
    }
}

The ViewModel

class UserViewModel(
    private val repository: UserRepository = UserRepository()
) : ViewModel() {
    private val _state = MutableStateFlow<UiState<UserResponse>>(UiState.Loading)
    val state = _state.asStateFlow()
    fun loadUser(id: Int) {
        viewModelScope.launch {
            _state.value = UiState.Loading
            repository.getUser(id)
                .onSuccess { _state.value = UiState.Success(it) }
                .onFailure { _state.value = UiState.Error(it.message ?: "Error") }
        }
    }
}

Observing in Activity

lifecycleScope.launch {
    viewModel.state.collect { state ->
        when (state) {
            is UiState.Loading -> showLoader()
            is UiState.Success -> showUser(state.data)
            is UiState.Error   -> showError(state.message)
        }
    }
}

Common Mistakes

• Calling API directly in Activity — always through ViewModel → Repository
• Using GlobalScope.launch — use viewModelScope so it cancels correctly
• Not handling errors in Repository — always wrap network calls in try/catch
• Exposing MutableStateFlow publicly — always expose as StateFlow