第一次发出 kotlin 协程后，MutableStateFlow 不发出值

Question

这是我的 FirebaseOTPVerificationOperation 类，其中定义了我的 MutableStateFlow 属性，并更改了值，

    @ExperimentalCoroutinesApi
class FirebaseOTPVerificationOperation @Inject constructor(
    private val activity: Activity,
    val logger: Logger
) {
    private val _phoneAuthComplete = MutableStateFlow<PhoneAuthCredential?>(null)
    val phoneAuthComplete: StateFlow<PhoneAuthCredential?>
        get() = _phoneAuthComplete

    private val _phoneVerificationFailed = MutableStateFlow<String>("")
    val phoneVerificationFailed: StateFlow<String>
        get() = _phoneVerificationFailed

    private val _phoneCodeSent = MutableStateFlow<Boolean?>(null)
    val phoneCodeSent: StateFlow<Boolean?>
        get() = _phoneCodeSent

    private val _phoneVerificationSuccess = MutableStateFlow<Boolean?>(null)
    val phoneVerificationSuccess: StateFlow<Boolean?>
        get() = _phoneVerificationSuccess

    fun resendPhoneVerificationCode(phoneNumber: String) {
        _phoneVerificationFailed.value = "ERROR_RESEND"
    }
}

这是我的视图模式，我在那里监听 stateflow 属性的变化，如下所示，

class OTPVerificationViewModal @AssistedInject constructor(
    private val coroutinesDispatcherProvider: AppCoroutineDispatchers,
    private val firebasePhoneVerificationListener: FirebaseOTPVerificationOperation,
    @Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel() {

    @AssistedInject.Factory
    interface Factory {
        fun create(savedStateHandle: SavedStateHandle): OTPVerificationViewModal
    }

    val phoneAuthComplete = viewModelScope.launch {
        firebasePhoneVerificationListener.phoneAuthComplete.filter {
            Log.e("1","filter auth $it")
            it.isNotNull()
        }.collect {
            Log.e("2","complete auth $it")
        }
    }

    val phoneVerificationFailed = viewModelScope.launch {
        firebasePhoneVerificationListener.phoneVerificationFailed.filter {
            Log.e("3","filter failed $it")
            it.isNotEmpty()
        }.collect {
            Log.e("4","collect failed $it")
        }
    }

    val phoneCodeSent = viewModelScope.launch {
        firebasePhoneVerificationListener.phoneCodeSent.filter {
            Log.e("5","filter code $it")
            it.isNotNull()
        }.collect {
            Log.e("6","collect code $it")
        }
    }

    val phoneVerificationSuccess = viewModelScope.launch {
        firebasePhoneVerificationListener.phoneVerificationSuccess.filter {
            Log.e("7","filter success $it")
            it.isNotNull()
        }.collect {
            Log.e("8","collect success $it")
        }
    }

    init {
        resendVerificationCode()
        secondCall()
    }

    private fun secondCall() {
        viewModelScope.launch(coroutinesDispatcherProvider.io) {
            delay(10000)
            resendVerificationCode()
        }
    }

    fun resendVerificationCode() {
        viewModelScope.launch(coroutinesDispatcherProvider.io) {
            firebasePhoneVerificationListener.resendPhoneVerificationCode(
                getNumber()
            )
        }
    }

    private fun getNumber() =
            "+9191111116055"
}

问题是 firebasePhoneVerificationListener.phoneVerificationFailed在第一次调用时在视图模式中触发， init { resendVerificationCode() }

但是对于 , 的第二次调用init { secondCall() }， firebasePhoneVerificationListener.phoneVerificationFailed在 viewmodal 中没有被触发，我不知道为什么会发生这种情况，任何原因或解释都会非常有用。

电流输出： filter auth null filter failed filter code null filter success null filter failed ERROR_RESEND collect failed ERROR_RESEND

预期输出： filter auth null filter failed filter code null filter success null filter failed ERROR_RESEND collect failed ERROR_RESEND filter failed ERROR_RESEND collect failed ERROR_RESEND

Answer 1

StateFlow 是 SharedFlow： https ://github.com/Kotlin/kotlinx.coroutines/issues/2034

我的文章中有更详细的描述：https://veldan1202.medium.com/kotlin-setup-sharedflow-31debf613b91

val shared = MutableSharedFlow(
    replay = 1,
    onBufferOverflow = BufferOverflow.DROP_OLDEST,
)
shared.tryEmit(value)

Answer 2

状态流发出的值被混合并且不会两次发出相同的连续结果，您可以认为好像条件检查正在验证旧的发出值不等于新发出的值。

当前输出：filter auth null filter failed filter code null filter success null filter failed ERROR_RESEND collect failed ERROR_RESEND

（过滤器失败 ERROR_RESEND 收集失败 ERROR_RESEND）这是与发出的旧值相同的值，因此您不会看到它们被发出。

Answer 3

使用 a Channel：这会在两次发送相同的值后发出。

1. 将此添加到您的 ViewModel

   val _intent = Channel(Channel.CONFLATED)

2. 使用send/放置值trySend

   _intent.send(intentLocal)

3. 观察流动

   _intent.consumeAsFlow().collect { // 做某事 }

Answer 4

Pankaj 的答案是正确的，StateFlow不会两次发出相同的值。正如文档所暗示的那样：

状态流中的值以Any.equals与distinctUntilChanged运算符类似的方式使用比较进行合并。它用于将传入的更新合并到valueinMutableStateFlow并在新值等于先前发出的值时抑制将值发射到收集器。

因此，要解决此问题，您可以创建一个包装类并覆盖equals(and hashCode) 方法以返回，false即使这些类实际上是相同的：

sealed class VerificationError {
    object Resend: VerificationError()

    override fun equals(other: Any?): Boolean {
        return false
    }

    override fun hashCode(): Int {
        return Random.nextInt()
    }
}