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我现在在 JetpackCompose 中有一个问题。问题是，当我从流中收集数据时，值是从 firebase 获取的，就像有一个侦听器一样，并且数据每次都在变化。但事实并非如此。

我不知道真正的问题是什么！

FirebaseSrcNav

suspend fun getName(uid: String): Flow<Resource.Success<Any?>> = flow {
    val query = userCollection.document(uid)
    val snapshot = query.get().await().get("username")
    emit(Resource.success(snapshot))
}

导航库

suspend fun getName(uid: String) = firebase.getName(uid)

主页查看模型

fun getName(uid: String): MutableStateFlow<Any?> {
    val name = MutableStateFlow<Any?>(null)
    viewModelScope.launch {
        navRepository.getName(uid).collect { nameState ->
            when (nameState) {
                is Resource.Success -> {
                    name.value = nameState.data
                    //_posts.value = state.data
                    loading.value = false
                }
                is Resource.Failure<*> -> {
                    Log.e(nameState.throwable, nameState.throwable)
                }
            }
        }
    }
    return name
}

我认为问题出在 HomeScreen 中，当我调用 collectasState().value 时。

主屏幕

val state = rememberLazyListState()
        LazyColumn(
            state = state,
            verticalArrangement = Arrangement.spacedBy(10.dp)
        ) {
            items(post) { post ->
                //val difference = homeViewModel.getDateTime(homeViewModel.getTimestamp())
                val date = homeViewModel.getDateTime(post.timeStamp!!)
                val name = homeViewModel.getName(post.postAuthor_id.toString()).collectAsState().value
                QuestionCard(
                    name = name.toString(),
                    date = date!!,
                    image = "",
                    text = post.postText!!,
                    like = 0,
                    response = 0,
                    topic = post.topic!!
                )
            }
        }

我无法发布视频，但如果您需要图像，请想象一个文本字段，其中测试每 0.005 秒在“null”和“MyName”之间交替。

4

1 回答 1

1

检查官方文档。

https://developer.android.com/kotlin/flow

流是异步的

在视图模型上

private val _name = MutableStateFlow<String>("")
    val name: StateFlow<String>
        get() = _name

fun getName(uid: String) {
    viewModelScope.launch {
        //asyn call
        navRepository.getName(uid).collect { nameState ->
            when (nameState) {
                is Resource.Success -> {
                    name.value = nameState.data
                }
                is Resource.Failure<*> -> {
                    //manager error
                    Log.e(nameState.throwable, nameState.throwable)
                }
            }
        }
    }
}

在你看来

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    ...
    lifecycleScope.launch {
        viewModel.name.collect { name -> handlename
        }
    }
}
于 2021-07-30T18:14:23.497 回答