结合流＆lt; list＆gt;和kotlin中的字符串

Question

嘿，我在Kotlin Flow工作。我有来自服务器的数据列表的流程。我想过滤文本，我尝试了一些代码，但这给了我问题。有人可以指导我吗？谢谢

ExploreViewModel.kt

class ExploreViewModel : BaseViewModel() {

    private val query = MutableStateFlow("")
    var queryText: String
        get() = query.value
        set(value) {
            query.value = value
        }
    val filteredTopics = MutableStateFlow<List<ConsultationTopics>>(emptyList())
    val filteredCategories = query
        .debounce(200) // low debounce because we are just filtering local data
        .distinctUntilChanged()
        .combine(filteredTopics) { queryText, categoriesList ->
            val criteria = queryText.lowercase()
            if (criteria.isEmpty()) {
                    return@combine filteredTopics
            } else {
                categoriesList.filter { category -> category.title?.lowercase()?.let { criteria.contains(it) } == true }
            }
        }
}

我有filteredTopics属性，这些数据来自服务器，queryText使用onqueryTextChange来自<代码>销售范围。我正在尝试过滤数据并创建名为filteredCategories的新属性，以将此值传递给适配器。我正在尝试filteredCategories我正在检查queryText是空的，然后将整个列表传递，否则仅通过过滤器列表，但是我不知道这是正确的方法。

错误

private fun setupFilteredTopic() {
        lifecycleScope.launchWhenCreated {
            repeatOnLifecycle(Lifecycle.State.CREATED) {
                viewModel.filteredCategories.collect { filteredTopicsList ->
                    consultationAdapter.submitList(filteredTopicsList)
                }
            }
        }
    }

有人可以指导我。谢谢

Answer 1

问题在于，您返回了过滤类型的不同类型的元素

if (criteria.isEmpty()) {
    return@combine filteredTopics // type MutableStateFlow<List<ConsultationTopics>>
} else {
    categoriesList.filter { category -> category.title?.lowercase()?.let { criteria.contains(it) } == true } // type List<ConsultationTopics>
}

，因此您需要对代码进行一些更改，更改return@combine filteredTopics by rether> return@combine@combine filteredtopics.value ：

class ExploreViewModel : BaseViewModel() {

    private val query = MutableStateFlow("")
    var queryText: String
        get() = query.value
        set(value) {
            query.value = value
        }
    val filteredTopics = MutableStateFlow<List<ConsultationTopics>>(emptyList())
    val filteredCategories = query
        .debounce(200) // low debounce because we are just filtering local data
        .distinctUntilChanged()
        .combine(filteredTopics) { queryText, categoriesList ->
            val criteria = queryText.lowercase()
            if (criteria.isEmpty()) {
                categoriesList
            } else {
                categoriesList.filter { category -> category.title?.lowercase()?.let { criteria.contains(it) } == true }
            }
        }
}

这应该解决错误

Answer 2

您应该返回ConsultationTopics 中的对象 combine 使用categoriesList而不是filteredtopics：

val criteria = queryText.lowercase()
return@combine if (criteria.isEmpty()) {
     categoriesList
} else {
     categoriesList.filter { category -> category.title?.lowercase()?.let { criteria.contains(it) } == true }
}

或我们可以忽略我们return@combine操作员：

val criteria = queryText.lowercase()
if (criteria.isEmpty()) {
     categoriesList
} else {
     categoriesList.filter { category -> category.title?.lowercase()?.let { criteria.contains(it) } == true }
}