在 IO 线程进程 kotlin 协程完成后运行主线程中的代码

Question

 override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

  lifecycleScope.launch(Dispatchers.Main) {
            networkviewModel.productist.collectLatest {
                when (it) {
                    Resource.Empty -> {
                        Log.e("product", "" + "empty")
                    }
                    is Resource.Failure -> {
                        Log.e("product", "" + "failure")
                    }
                    Resource.Loading -> {

                    }
                    is Resource.Success -> {
                        val response = it.value
                        Log.e("test","success response")
                        val products: List<Products> = response.data
                        val variants: List<Variants> = response.data.map { it.variants }.flatten()
                        lifecycleScope.launch(Dispatchers.IO) {
                            productRoom.insertProducts(products)
                            productRoom.insertVariants(variants)
                            val subcategoryid = SubCategoryList(response.data[0].subcategory_id!!.toInt())
                            productRoom.insertSubCat(subcategoryid)
                        }
                        subcat_id = response.data[0].subcategory_id!!.toInt()
                        roomviewModel.productFlow.collectLatest{
                            Log.e("test","flow success from network room")
                            //    Log.e("test",it.toString())
                            LoadingUtils.hideDialog()
                            proadapter.setMutableArraylist(it)
                            proadapter.notifyDataSetChanged()
                        }
                    }
                }
            }
        }
}

我收到致命异常错误：主进程：com.store.pasumainew，PID：13125 java.lang.IndexOutOfBoundsException：索引：0，大小：0

因为在 Resource.Success -> collect 在 IO 线程进程完成之前调用

我想完成 IO 线程，然后从房间收集值

Answer 1

在收集之前尝试使用withContext(Dispatchers.IO) ，它将被暂停，直到所有操作完成：

withContext(Dispatchers.IO) {                
    productRoom.insertProducts(products)
    productRoom.insertVariants(variants)
    val subcategoryid = SubCategoryList(response.data[0].subcategory_id!!.toInt())
    productRoom.insertSubCat(subcategoryid)
}
// ... collecting code

顺便说一句，您不需要使用Dispatchers.Main来启动主协程，默认情况下， lifecycleScope适用于Dispatchers.Main上下文，因此您只需编写：

lifecycleScope.launch {
    // ...
}

Answer 2

崩溃就在这行代码中

val subcategoryid = SubCategoryList(response.data[0].subcategory_id!!.toInt())

尝试将其更改为此

val subcategoryid = SubCategoryList(response.data[0]?.subcategory_id?.toInt())?:0