Kotlin词典APP数据异常求助：Flow无数据显示问题排查

问题现象 #

使用Kotlin开发词典APP，采用MVVM+Clean架构，通过Jsoup从网络抓取词汇信息，用Flow传递数据，但出现以下问题：

• 界面无词汇数据展示
• 控制台仅输出kotlinx.coroutines.flow.SafeFlow@1493a74
• MostUsedWordScreen中打印的state.mostWordUsedItems为空列表[]

相关代码 #

ExtractedData（数据实体类） #

data class ExtractedData(
    var id :Int = 0,
    var word:String = "",
    var meaning :String = ""
)

WordInfoRepositoryImpl（数据层实现） #

class WordInfoRepositoryImpl @Inject constructor(
    private val api:DictionaryApi
) : WordInfoRepository {

    // 从网络获取词汇及释义
    override fun getEventsList(): Flow<Resource<MutableList<ExtractedData>>> = flow {
        emit(Resource.Loading())
        val listData = mutableListOf<ExtractedData>()

        try {
            val url = "https://ielts.com.au/australia/prepare/article-100-new-english-words-and-phrases-updated-2020"
            val doc = withContext(Dispatchers.IO){
                Jsoup.connect(url).get() // 提示"Inappropriate blocking method call"，但已放在IO协程中
            }

            val table = doc.select("table")
            val rows = table.select("tr")
            val eventsSize = rows.size

            for (i in 1 until eventsSize) {
                val row = rows[i]
                val cols = row.select("td")
                val word = cols[0].text()
                val meaning = cols[1].text()
                listData.add(ExtractedData(i,word,meaning))
            }
        } catch (e: IOException) {
            emit(Resource.Error("IO Exception"))
        } catch (e : HttpException) {
            emit(Resource.Error("HTTP EXCEPTION"))
        }

        emit(Resource.Success(listData))
    }
}

WordInfoRepository（领域层接口） #

interface WordInfoRepository {
    fun getEventsList(): Flow<Resource<MutableList<ExtractedData>>>
}

GetWordsAndMeaningsOnTheInternetUseCase（领域层用例） #

class GetWordsAndMeaningsOnTheInternetUseCase@Inject constructor(
    private val repository: WordInfoRepository
){
    operator fun invoke() : Flow<Resource<MutableList<ExtractedData>>> {
        return repository.getEventsList()
    }
}

MostUsedWordScreenViewModel（ViewModel层） #

@HiltViewModel
class MostUsedWordScreenViewModel @Inject constructor(
    private val getWordsAndMeaningsOnTheInternetUseCase: GetWordsAndMeaningsOnTheInternetUseCase
) : ViewModel() {

    private var searchJob: Job? = null
    private val _state = mutableStateOf(MostUsedWordState())
    val state: State<MostUsedWordState> = _state

    init {
        fetchData()
    }

    private fun fetchData()  {
        searchJob?.cancel()
        searchJob = viewModelScope.launch(IO) {
            getWordsAndMeaningsOnTheInternetUseCase().onEach { result ->
                when (result) {
                    is Resource.Success -> {
                        _state.value = state.value.copy(
                            mostWordUsedItems = result.data ?: mutableListOf(),
                            isLoading = false
                        )
                    }
                    is Resource.Error -> {
                        _state.value = state.value.copy(
                            mostWordUsedItems = result.data ?: mutableListOf(),
                            isLoading = false
                        )
                    }
                    is Resource.Loading -> {
                        _state.value = state.value.copy(
                            mostWordUsedItems = result.data ?: mutableListOf(),
                            isLoading = true
                        )
                    }
                }
            }
        }
    }
}

MostUsedWordScreen（UI层） #

@Composable
fun MostUsedWordScreen(viewModel: MostUsedWordScreenViewModel = hiltViewModel()) {
    val state = viewModel.state.value
    println("state --- >>> "+state.mostWordUsedItems)
    LazyColumn(modifier = Modifier.fillMaxSize()) {
        items(state.mostWordUsedItems.size) { i ->
            val wordInfo = state.mostWordUsedItems[i]
            if(i > 0) {
                Spacer(modifier = Modifier.height(8.dp))
            }
            MostUsedWordItem(word = wordInfo)
            if(i < state.mostWordUsedItems.size - 1) {
                Divider()
            }
        }
    }
}

@Composable
fun MostUsedWordItem(word : ExtractedData ) {
    Column(modifier = Modifier
        .padding(5.dp)
        .fillMaxWidth()) {
        Text(text = word.word,
            modifier = Modifier.padding(3.dp),
            textAlign = TextAlign.Center,
            fontSize = 18.sp)
    }
}

问题定位与解决方案 #

核心问题：Flow未被收集 #

Flow是冷流，只有被收集时才会执行流中的逻辑。原ViewModel代码中，getWordsAndMeaningsOnTheInternetUseCase().onEach { ... }仅定义了流的转换操作，但没有启动收集，导致整个网络请求和数据解析逻辑完全没执行，自然没有数据更新到UI状态。

修复代码（ViewModel的fetchData方法）

将onEach配合launchIn启动收集，或者直接使用collect：

private fun fetchData()  {
    searchJob?.cancel()
    searchJob = viewModelScope.launch {
        getWordsAndMeaningsOnTheInternetUseCase()
            .onEach { result ->
                when (result) {
                    is Resource.Success -> {
                        _state.value = state.value.copy(
                            mostWordUsedItems = result.data ?: mutableListOf(),
                            isLoading = false
                        )
                    }
                    is Resource.Error -> {
                        _state.value = state.value.copy(
                            mostWordUsedItems = result.data ?: mutableListOf(),
                            isLoading = false
                        )
                    }
                    is Resource.Loading -> {
                        _state.value = state.value.copy(
                            // Loading状态保留原有数据，避免列表清空
                            isLoading = true
                        )
                    }
                }
            }
            // 启动Flow收集
            .launchIn(viewModelScope)
    }
}

次要优化点 #

1. Loading状态保留原有数据：原代码在Loading时会把mostWordUsedItems设为空列表，导致界面清空，建议仅更新isLoading状态，保留现有数据。
2. Jsoup选择器准确性：检查目标页面的HTML结构，确保doc.select("table")能正确定位到包含词汇的表格，必要时使用更精确的选择器（比如doc.select("table[class='some-class']")）。
3. Jsoup阻塞警告：虽然不影响功能，但可以通过@Suppress("BlockingMethodInNonBlockingContext")注解消除警告，或者将整个Jsoup操作块放在withContext(Dispatchers.IO)内（已做）。

内容的提问来源于stack exchange，提问作者NewPartizal