为什么 Activity 类中的生命周期作用域没有响应？

Question

当我点击负责类别的类别RecycleView（categoryRecyclerView）中的某个项目时，分类代码发生变化。 之后的目标是从goodsRecyclerView相应地重新生成recyclerView。

第一次运行它时，它被完全调用，但当你更改类别时它不会反映。

在ViewModel中，_selectSubDispClasSeq是类别分类代码，我想在_goods中反映它。

---

下面是我的代码。

@AndroidEntryPoint 类 DetailCategoryActivity : BaseActivity({ ActivityDetailCategoryBinding.inflate(it)}) {

private val viewModel: DetailCategoryViewModel by viewModels()

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(binding.root)

    val dispClasSeq = intent.getIntExtra("dispClasSeq", 0)

    val categoryRecyclerView = binding.rvSublistCategory
    val categoryLayoutManager = GridLayoutManager(this, 3)

    val categoryAdapter = SubListAdapter(emptyList()) { selectedDispClasItem ->
        viewModel.onSubItemClicked(selectedDispClasItem)
    }

    categoryRecyclerView.adapter = categoryAdapter
    categoryRecyclerView.layoutManager = categoryLayoutManager


    val goodsRecyclerView = binding.rvGoods
    val goodsLayoutManager = GridLayoutManager(this, 2)

    val goodsAdapter = GoodsAdapter()
    goodsRecyclerView.adapter = goodsAdapter
    goodsRecyclerView.layoutManager = goodsLayoutManager

    lifecycleScope.launch {
        viewModel.subDispClasInfos.collect { subDispClasInfos ->
            viewModel.loadSubDispClasInfos(dispClasSeq)
            categoryAdapter.submitList(subDispClasInfos)
        }
    }

    lifecycleScope.launch {
        viewModel.goods.collect { goods ->
            Log.d("goods", goods.toString())
            val subDsipClasSeq = viewModel.selectedSubDispClasSeq.value
            viewModel.loadGoodsInfos(dispClasSeq, subDsipClasSeq, "추천순")
            goodsAdapter.submitData(goods)
        }
    }

}

}

@HiltViewModel

类 DetailCategoryViewModel @Inject 构造函数（ 私有 valDetailItemRepository：DetailItemRepository， 私人 val GoodsItemRepository：GoodsItemRepository ) : ViewModel() {

private val _subDispClasInfos = MutableStateFlow<List<DetailCategoryItem>>(emptyList())
val subDispClasInfos: StateFlow<List<DetailCategoryItem>> get() = _subDispClasInfos

private val _goods: MutableStateFlow<PagingData<Goods>> = MutableStateFlow(PagingData.empty())
val goods: StateFlow<PagingData<Goods>> get() = _goods

private val _selectedSubDispClasSeq = MutableStateFlow(0)
val selectedSubDispClasSeq: StateFlow<Int> get() = _selectedSubDispClasSeq

fun loadSubDispClasInfos(dispClasSeq: Int) {
    viewModelScope.launch {
        try {
            detailItemRepository.getCategorySublistItemsFlow(dispClasSeq).collect { result ->
                _subDispClasInfos.emit(result)
            }
        } catch (e: Exception) {
            Log.d("result", e.toString())
        }
    }
}

fun loadGoodsInfos(prntsDispClasSeq: Int, subDispClasSeq: Int, searchValue: String) {
    viewModelScope.launch {
        try {
            Log.d("loadGoodsInfos1", subDispClasSeq.toString())
            val result = goodsItemRepository.getGoodsItemsFlow(prntsDispClasSeq, subDispClasSeq, searchValue)
                .first()
            _goods.emit(result)
        } catch (e: Exception) {
            Log.d("result", e.toString())
        }
    }
}

fun onSubItemClicked(item: DetailCategoryItem) {
    viewModelScope.launch {
        _selectedSubDispClasSeq.emit(item.dispClasSeq)
        loadGoodsInfos(item.prntsDispClasSeq, selectedSubDispClasSeq.value, "추천순")
    }
}

}

当我输出日志时，确认了loadGoodsInfos函数中_selectedSubDispClasSeq的值变化正常。但我在活动课上观察不到。

lifecycleScope.launch {
        viewModel.goods.collect { goods ->
            Log.d("goods", goods.toString())
            val subDsipClasSeq = viewModel.selectedSubDispClasSeq.value
            viewModel.loadGoodsInfos(dispClasSeq, subDsipClasSeq, "추천순")
            goodsAdapter.submitData(goods)
        }
    }

Answer 1

看起来问题可能与以下事实有关：您正在收集

goods

块内的

lifecycleScope.launch

流，但您没有在同一协程范围内观察到

_selectedSubDispClasSeq

的更改。因此，对

_selectedSubDispClasSeq

的更改可能不会反映在

goods

流集合中。

要解决此问题，您可以尝试使用

combine

包中的

kotlinx.coroutines.flow

运算符组合两个流。

combine

运算符允许您观察多个流并对其中任何一个流的变化做出反应。以下是修改代码的方法：

lifecycleScope.launch {
    combine(viewModel.selectedSubDispClasSeq, viewModel.goods) { subDispClasSeq, goods ->
        Log.d("goods", goods.toString())
        viewModel.loadGoodsInfos(dispClasSeq, subDispClasSeq, "추천순")
        goodsAdapter.submitData(goods)
    }.collect()
}

确保导入 kotlinx.coroutines.flow.combine 函数：

import kotlinx.coroutines.flow.combine

这应该有助于确保在更新

_selectedSubDispClasSeq

流程时正确观察到

goods

中的变化。