进程死亡后恢复共享ViewModel的问题

如何解决进程死亡后恢复共享ViewModel的问题

我到目前为止所拥有的。

订单列表屏幕：显示订单列表。单击订单后，将显示与该订单关联的产品列表。

class OrderListFragment : Fragment() {
    //skipped irrelevant code

    override fun onViewCreated(view: View,savedInstanceState: Bundle?) {
        //skipped irrelevant code

        recyclerView.adapter = Adapter(orderList) { order ->
            //This is called when an item is clicked in the order list.

            findNavController()
                .navigate(R.id.order_product_graph,ProductListFragment.constructArguments(order))
        }
    }

}

与所有这些关联的导航图。

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/shopper_nav_graph"
    app:startDestination="@id/shopperHomeFragment2">

    <fragment
        android:id="@+id/orderListFragment"
        android:name="com.example.OrderListFragment"
        android:label="OrderListFragment"
        tools:layout="@layout/order_list_fragment" />

    <navigation
        android:id="@+id/order_product_graph"
        app:startDestination="@id/productListFragment">
        <fragment
            android:id="@+id/productListFragment"
            android:name="com.example.ProductListFragment"
            android:label="ProductListFragment"
            tools:layout="@layout/item_list_fragment">

        </fragment>
        <fragment
            android:id="@+id/productFragment"
            android:name="com.example.ProductFragment"
            android:label="ProductFragment"
            tools:layout="@layout/item_fragment" />

        <fragment
            android:id="@+id/PLUProductFragment"
            android:name="com.example.PLUProductFragment"
            android:label="PLUProductFragment" />
    </navigation>
   
    <!--    Skipped irrelevant code-->
 
</navigation>

产品列表屏幕：显示与订单关联的产品列表。在参数包中使用order。

class ProductListFragment: Fragment(){
    //skipped irrelevant code

    lateinit var viewModel: ProductListViewModel

    override fun onViewCreated(view: View,savedInstanceState: Bundle?) {
        //skipped irrelevant code

        val order = arguments?.getSerializable(KEY_ORDER) as ShopperOrder
        viewModel = ViewModelProvider(
            findNavController().getViewModelStoreOwner(R.id.order_item_graph),// this viewmodel will be shared with ProductFragment so using the nested graph as store owner.
            ProductListViewModelFactory(order)// Note this viewModel takes a order parameter
        ).get(ProductListViewModel::class.java)

        viewModel.products.observe(viewLifecycleOwner,Observer { products ->
            //This is called when a product is clicked in the product list

            viewBinding.recyclerView.adapter = ProductListAdapter(products) { product->
                findNavController()
                .navigate(R.id.productFragment,ProductFragment.constructArguments(product))
            }

        }
    }

}

产品屏幕：显示产品详细信息。这里有一个下拉列表，用于选择产品是否可用，缺货，已移除，已更换等。此屏幕应将数据从下拉列表发送到ProductListScreen，在此列表中更新以显示此数据。**

class ProductFragment: Fragment(){

    //skipped irrelevant code

    lateinit var parentViewModel: ProductListViewModel
    lateinit var viewModel: ProductViewModel
    lateinit var product: Product

    override fun onViewCreated(view: View,savedInstanceState: Bundle?) {
        //skipped irrelevant code

        product = arguments?.getSerializable(KEY_PRODUCT) as Product
        parentViewModel = ViewModelProvider(
            findNavController().getViewModelStoreOwner(R.id.order_item_graph),// this viewmodel will is shared with ProductListFragment so using the nested graph as store owner.
        ).get(ProductListViewModel::class.java)
        //Crash occurs here,when trying to get the shared ProductListViewModel after process death. Read details below

        //this ViewModel takes the ProductListViewModel as parentViewModel param
        viewModel = ViewModelProvider(this,ProductViewModel.Factory(product,parentViewModel)).get(ProductViewModel::class.java)

    }
   
    fun productStatusSelected(status: String){
        parentViewModel.updateProductStatus(product,status)
        findNavController().popBackStack()
    }

}

场景 订单列表>产品列表>产品>单击主页按钮>做了很多其他事情>返回到应用程序> 崩溃

发生的情况是，当ProductFragment重新创建代码以调用共享的ProductListViewModel时，ProductListViewModel应该采用此处未提供的订单参数，并且由于InstantiationException崩溃。 ItemListViewModel类没有零参数构造函数。

错误消息非常清楚，我想知道在这里应该使用哪种策略才能使ViewModel工作。