android-kotlin-development

Build robust native Android applications using Kotlin with modern architecture patterns, Jetpack libraries, and Compose for declarative UI.

• Creating native Android applications with best practices • Using Kotlin for type-safe development • Implementing MVVM architecture with Jetpack • Building modern UIs with Jetpack Compose • Integrating with Android platform APIs

`kotlin // Models data class User( val id: String, val name: String, val email: String, val avatarUrl: String? = null ) data class Item( val id: String, val title: String, val description: String, val imageUrl: String? = null, val price: Double ) // API Service with Retrofit interface ApiService { @GET("/users/{id}") suspend fun getUser(@Path("id") userId: String): User @PUT("/users/{id}") suspend fun updateUser( @Path("id") userId: String, @Body user: User ): User @GET("/items") suspend fun getItems(@Query("filter") filter: String = "all"): List<Item> @POST("/items") suspend fun createItem(@Body item: Item): Item } // Network client setup @Module @InstallIn(SingletonComponent::class) object NetworkModule { @Provides @Singleton fun provideRetrofit(): Retrofit { val httpClient = OkHttpClient.Builder() .addInterceptor { chain -> val original = chain.request() val requestBuilder = original.newBuilder() val token = PreferencesManager.getToken() if (token.isNotEmpty()) { requestBuilder.addHeader("Authorization", "Bearer $token") } requestBuilder.addHeader("Content-Type", "application/json") chain.proceed(requestBuilder.build()) } .connectTimeout(30, TimeUnit.SECONDS) .readTimeout(30, TimeUnit.SECONDS) .build() return Retrofit.Builder() .baseUrl("https://api.example.com") .client(httpClient) .addConverterFactory(GsonConverterFactory.create()) .build() } @Provides @Singleton fun provideApiService(retrofit: Retrofit): ApiService { return retrofit.create(ApiService::class.java) } } `

`kotlin @HiltViewModel class UserViewModel @Inject constructor( private val apiService: ApiService ) : ViewModel() { private val _user = MutableStateFlow<User?>(null) val user: StateFlow<User?> = _user.asStateFlow() private val _isLoading = MutableStateFlow(false) val isLoading: StateFlow<Boolean> = _isLoading.asStateFlow() private val _errorMessage = MutableStateFlow<String?>(null) val errorMessage: StateFlow<String?> = _errorMessage.asStateFlow() fun fetchUser(userId: String) { viewModelScope.launch { _isLoading.value = true _errorMessage.value = null try { val user = apiService.getUser(userId) _user.value = user } catch (e: Exception) { _errorMessage.value = e.message ?: "Unknown error" } finally { _isLoading.value = false } } } fun logout() { _user.value = null } } @HiltViewModel class ItemsViewModel @Inject constructor( private val apiService: ApiService ) : ViewModel() { private val _items = MutableStateFlow<List<Item>>(emptyList()) val items: StateFlow<List<Item>> = _items.asStateFlow() private val _isLoading = MutableStateFlow(false) val isLoading: StateFlow<Boolean> = _isLoading.asStateFlow() fun fetchItems(filter: String = "all") { viewModelScope.launch { _isLoading.value = true try { val items = apiService.getItems(filter) _items.value = items } catch (e: Exception) { println("Error fetching items: ${e.message}") } finally { _isLoading.value = false } } } fun addItem(item: Item) { viewModelScope.launch { try { val created = apiService.createItem(item) _items.value = _items.value + created } catch (e: Exception) { println("Error creating item: ${e.message}") } } } } `