Kotlin coroutines da thay doi hoan toan cach lap trinh bat dong bo tren Android. Thoi dai cua callback hell va AsyncTask loi thoi da qua: voi coroutines, ma bat dong bo duoc viet giong nhu ma dong bo, dong thoi van dam bao hieu suat va kha nang bao tri.

Tai sao chon coroutines?

Coroutines co trong luong nhe (hang ngan coroutine co the chay tren mot thread duy nhat), ho tro huy tu dong, va tich hop lien mach voi Jetpack cung he sinh thai Android hien dai.

Hieu ro cac khai niem co ban

Truoc khi bat dau viet code, can nam vung nhung diem lam cho coroutines tro nen manh me.

Coroutine la gi?

Coroutine la mot the hien cua phep tinh co kha nang tam dung. Khac voi thread, coroutine khong chan (block): chung tam dung thuc thi va giai phong thread cho cac tac vu khac.

BasicCoroutine.ktkotlin

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch {
        delay(1000L) // Suspend without blocking
        println("World!")
    }
    println("Hello,")
}
// Output: Hello, World!

Suspend Functions: Trai tim cua Coroutines

Tu khoa suspend chi ra rang mot ham co the tam dung viec thuc thi coroutine ma khong chan thread.

SuspendFunction.ktkotlin

suspend fun fetchUserData(userId: String): User {
    return withContext(Dispatchers.IO) {
        // Network call - runs on an IO thread
        apiService.getUser(userId)
    }
}

suspend fun fetchUserWithPosts(userId: String): UserWithPosts {
    // Sequential execution
    val user = fetchUserData(userId)
    val posts = fetchUserPosts(userId)
    return UserWithPosts(user, posts)
}

Quy tac vang: Mot suspend function chi co the duoc goi tu mot suspend function khac hoac tu ben trong mot coroutine.

Coroutine Scopes: Quan ly vong doi

Scope xac dinh vong doi cua coroutines. Day la yeu to then chot de tranh ro ri bo nho.

viewModelScope: Scope danh cho ViewModel

UserViewModel.ktkotlin

class UserViewModel(
    private val userRepository: UserRepository
) : ViewModel() {

    private val _uiState = MutableStateFlow<UserUiState>(UserUiState.Loading)
    val uiState: StateFlow<UserUiState> = _uiState.asStateFlow()

    fun loadUser(userId: String) {
        viewModelScope.launch {
            _uiState.value = UserUiState.Loading

            try {
                val user = userRepository.getUser(userId)
                _uiState.value = UserUiState.Success(user)
            } catch (e: Exception) {
                _uiState.value = UserUiState.Error(e.message)
            }
        }
    }
}

sealed class UserUiState {
    object Loading : UserUiState()
    data class Success(val user: User) : UserUiState()
    data class Error(val message: String?) : UserUiState()
}

lifecycleScope: Danh cho Activity va Fragment

UserFragment.ktkotlin

class UserFragment : Fragment() {

    private val viewModel: UserViewModel by viewModels()

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        viewLifecycleOwner.lifecycleScope.launch {
            viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
                viewModel.uiState.collect { state ->
                    when (state) {
                        is UserUiState.Loading -> showLoading()
                        is UserUiState.Success -> showUser(state.user)
                        is UserUiState.Error -> showError(state.message)
                    }
                }
            }
        }
    }
}

Canh bao ve ro ri bo nho

Khong bao gio su dung GlobalScope trong ung dung Android. Cac coroutine khoi chay bang GlobalScope khong gan voi bat ky vong doi nao va co the gay ro ri bo nho.

Dispatchers: Kiem soat luong thuc thi

Dispatchers xac dinh coroutine se chay tren thread nao.

4 Dispatcher chinh

Dispatchers.ktkotlin

// Main: main thread (UI)
viewModelScope.launch(Dispatchers.Main) {
    textView.text = "UI update"
}

// IO: I/O operations (network, database)
viewModelScope.launch(Dispatchers.IO) {
    val data = repository.fetchFromNetwork()
}

// Default: CPU-intensive computations
viewModelScope.launch(Dispatchers.Default) {
    val result = heavyComputation(data)
}

// Unconfined: inherits caller context (rare use)

withContext: Chuyen doi Dispatcher

ImageProcessor.ktkotlin

class ImageProcessor {

    suspend fun processImage(bitmap: Bitmap): Bitmap {
        return withContext(Dispatchers.Default) {
            // CPU-intensive processing on Default
            applyFilters(bitmap)
        }
    }

    suspend fun saveToGallery(bitmap: Bitmap) {
        withContext(Dispatchers.IO) {
            // Disk write on IO
            saveToFile(bitmap)
        }
    }
}

// Usage in ViewModel
viewModelScope.launch {
    val processed = imageProcessor.processImage(originalBitmap)
    imageProcessor.saveToGallery(processed)
    // Automatic return to Main for UI update
    _uiState.value = UiState.Success(processed)
}

Thuc thi song song voi async/await

De thuc thi nhieu tac vu dong thoi va ket hop ket qua, su dung async.

ParallelExecution.ktkotlin

suspend fun loadDashboard(): Dashboard {
    return coroutineScope {
        // Parallel launch
        val userDeferred = async { userRepository.getUser() }
        val statsDeferred = async { statsRepository.getStats() }
        val notificationsDeferred = async { notificationRepository.getNotifications() }

        // Await results
        Dashboard(
            user = userDeferred.await(),
            stats = statsDeferred.await(),
            notifications = notificationsDeferred.await()
        )
    }
}

Hieu suat

Voi async, ca 3 loi goi duoc thuc thi song song. Neu moi loi goi mat 1 giay, tong thoi gian chi khoang 1 giay thay vi 3 giay khi thuc thi tuan tu.

Xu ly loi trong Coroutines

try/catch truyen thong

ErrorHandling.ktkotlin

viewModelScope.launch {
    try {
        val user = userRepository.getUser(userId)
        _uiState.value = UiState.Success(user)
    } catch (e: HttpException) {
        _uiState.value = UiState.Error("Server error: ${e.code()}")
    } catch (e: IOException) {
        _uiState.value = UiState.Error("Network error")
    } catch (e: Exception) {
        _uiState.value = UiState.Error("Unexpected error")
    }
}

CoroutineExceptionHandler

ExceptionHandler.ktkotlin

class UserViewModel : ViewModel() {

    private val exceptionHandler = CoroutineExceptionHandler { _, throwable ->
        _uiState.value = UiState.Error(throwable.message)
        Timber.e(throwable, "Error in coroutine")
    }

    fun loadUser(userId: String) {
        viewModelScope.launch(exceptionHandler) {
            val user = userRepository.getUser(userId)
            _uiState.value = UiState.Success(user)
        }
    }
}

Result Wrapper Pattern

ResultPattern.ktkotlin

sealed class Result<out T> {
    data class Success<T>(val data: T) : Result<T>()
    data class Error(val exception: Throwable) : Result<Nothing>()
}

suspend fun <T> safeApiCall(apiCall: suspend () -> T): Result<T> {
    return try {
        Result.Success(apiCall())
    } catch (e: Exception) {
        Result.Error(e)
    }
}

// Usage
class UserRepository(private val api: UserApi) {
    suspend fun getUser(id: String): Result<User> = safeApiCall {
        api.getUser(id)
    }
}

// In ViewModel
viewModelScope.launch {
    when (val result = userRepository.getUser(userId)) {
        is Result.Success -> _uiState.value = UiState.Success(result.data)
        is Result.Error -> _uiState.value = UiState.Error(result.exception.message)
    }
}

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Khám phá Android

Huy coroutine: Don dep tai nguyen dung cach

Coroutines ho tro co che huy hop tac (cooperative cancellation). Day la dieu can thiet de tranh ro ri tai nguyen.

Tu dong huy voi Scopes

SearchViewModel.ktkotlin

class SearchViewModel : ViewModel() {

    private var searchJob: Job? = null

    fun search(query: String) {
        // Cancel previous search
        searchJob?.cancel()

        searchJob = viewModelScope.launch {
            delay(300) // Debounce
            val results = searchRepository.search(query)
            _searchResults.value = results
        }
    }
}

Kiem tra trang thai huy

CancellationCheck.ktkotlin

suspend fun processLargeList(items: List<Item>) {
    items.forEach { item ->
        // Check if coroutine is cancelled
        ensureActive()

        processItem(item)
    }
}

suspend fun downloadFiles(urls: List<String>) = coroutineScope {
    urls.map { url ->
        async {
            try {
                downloadFile(url)
            } catch (e: CancellationException) {
                cleanupPartialDownload(url)
                throw e // Re-throw to propagate cancellation
            }
        }
    }.awaitAll()
}

Khong bao gio nuot CancellationException: neu bat Exception, can nem lai CancellationException de viec huy duoc lan truyen dung cach.

Flow: Lap trinh phan ung

Flow la tuong duong cua RxJava Observable trong the gioi coroutines, nhung don gian hon va tich hop san.

Tao va thu thap Flow

FlowBasics.ktkotlin

fun getUsers(): Flow<List<User>> = flow {
    while (true) {
        val users = userApi.getUsers()
        emit(users)
        delay(5000) // Poll every 5 seconds
    }
}

// Flow from Room
@Dao
interface UserDao {
    @Query("SELECT * FROM users")
    fun getAllUsers(): Flow<List<User>>
}

// Collecting in ViewModel
viewModelScope.launch {
    userDao.getAllUsers()
        .catch { e -> _uiState.value = UiState.Error(e.message) }
        .collect { users ->
            _uiState.value = UiState.Success(users)
        }
}

StateFlow va SharedFlow

StateFlowVsSharedFlow.ktkotlin

class EventViewModel : ViewModel() {

    // StateFlow: keeps last value, ideal for UI state
    private val _uiState = MutableStateFlow(UiState.Initial)
    val uiState: StateFlow<UiState> = _uiState.asStateFlow()

    // SharedFlow: for one-shot events (navigation, snackbar)
    private val _events = MutableSharedFlow<UiEvent>()
    val events: SharedFlow<UiEvent> = _events.asSharedFlow()

    fun onButtonClick() {
        viewModelScope.launch {
            _events.emit(UiEvent.NavigateToDetail)
        }
    }
}

sealed class UiEvent {
    object NavigateToDetail : UiEvent()
    data class ShowSnackbar(val message: String) : UiEvent()
}

Cac toan tu Flow thiet yeu

FlowOperators.ktkotlin

userRepository.getUsers()
    .map { users -> users.filter { it.isActive } }
    .distinctUntilChanged()
    .debounce(300)
    .flatMapLatest { users ->
        fetchUserDetails(users)
    }
    .catch { e ->
        emit(emptyList())
    }
    .onEach { users ->
        analytics.logUserCount(users.size)
    }
    .stateIn(
        scope = viewModelScope,
        started = SharingStarted.WhileSubscribed(5000),
        initialValue = emptyList()
    )

Cac pattern nang cao

Retry voi Exponential Backoff

RetryPattern.ktkotlin

suspend fun <T> retryWithBackoff(
    times: Int = 3,
    initialDelay: Long = 100,
    maxDelay: Long = 1000,
    factor: Double = 2.0,
    block: suspend () -> T
): T {
    var currentDelay = initialDelay
    repeat(times - 1) { attempt ->
        try {
            return block()
        } catch (e: Exception) {
            Timber.w("Attempt ${attempt + 1} failed, retrying in ${currentDelay}ms")
        }
        delay(currentDelay)
        currentDelay = (currentDelay * factor).toLong().coerceAtMost(maxDelay)
    }
    return block()
}

// Usage
val user = retryWithBackoff {
    userApi.getUser(userId)
}

Timeout

TimeoutPattern.ktkotlin

suspend fun fetchWithTimeout() {
    try {
        val result = withTimeout(5000L) {
            api.fetchData()
        }
        processResult(result)
    } catch (e: TimeoutCancellationException) {
        showError("Request took too long")
    }
}

// Or with a default value
val result = withTimeoutOrNull(5000L) {
    api.fetchData()
} ?: defaultValue

Ket luan

Kotlin coroutines da tro thanh cong cu khong the thieu trong phat trien Android hien dai. Chung mang den cach tiep can bat dong bo thanh lich va hieu qua, tich hop hoan hao voi he sinh thai Jetpack.

Danh sach kiem tra

Su dung viewModelScope va lifecycleScope de tranh ro ri bo nho
Chon dung Dispatcher (Main, IO, Default)
Xu ly loi bang try/catch hoac Result wrapper
Trien khai co che huy hop tac
Su dung Flow cho cac luong du lieu phan ung
Uu tien StateFlow cho trang thai UI, SharedFlow cho su kien

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Tạo tài khoản miễn phí

Viec lam chu coroutines se mang lai loi the dang ke trong cac du an Android va phong van ky thuat. Hay thuc hanh thuong xuyen va kham pha cac pattern nang cao.

Kotlin Coroutines cho Android: Huong dan day du 2026