Android 如何从流量中重设值<；列表<；Obj>&燃气轮机；并将它们全部添加到<；列表<；Int>>；？

在ViewModel中：

val drillerCatList: List<Int> = emptyList()

val shownCategoriesFlow = wordDao.getShownCategories() // which returns type Flow<List<CategoryItem>>

---

如何从shownCategoriesFlow:FLow中检索所有categoryNumber值，并在ViewModel中使用这些值填充drillerCatList:List？

首先使drillerCatList可变，如下所示：

val drillerCatList: ArrayList<Int> = ArrayList()

---

首先，您的属性需要是

MutableList

或

var

。通常，带有只读

列表的
var
更可取，因为它不太容易出错。然后在一个协同程序中调用流上的
collect
collect
的行为类似于Iterable上的forEach

行为，只是当元素准备就绪时，它不会阻塞其间的线程

val drillerCatList: List<Int> = emptyList()

val shownCategoriesFlow = wordDao.getShownCategories()

init { // or you could put this in a function do do it passively instead of eagerly
    viewModelScope.launch {
        shownCategoriesFlow.collect { drillerCatList = it.map(CategoryItem::categoryNumber) }
    }
}

shownCategoriesFlow.collect {
   it.forEach{ categoryItem ->
        drillerCatList.add(categoryItem.categoryNumber)
   }
}

val drillerCatList: List<Int> = emptyList()

val shownCategoriesFlow = wordDao.getShownCategories()

init { // or you could put this in a function do do it passively instead of eagerly
    viewModelScope.launch {
        shownCategoriesFlow.collect { drillerCatList = it.map(CategoryItem::categoryNumber) }
    }
}

init {
    shownCategoriesFlow
        .onEach { drillerCatList = it.map(CategoryItem::categoryNumber) }
        .launchIn(viewModelScope)
}