在Android组合导航中，导航参数以 savedstatehandle 填充，然后可以在 viewModel 中访问。我在实践中做到了这一点，并且在此处概述了实施： 。
我的问题是我找不到有关为什么/如何发生的任何文件。实际上，我什至找不到官方文档，甚至没有提及 SavedStateHandle 中的导航参数。我很想阅读更多有关此的信息。我已经阅读了这些文档（以及更多），但没有在主题上找到：
https://develiper.android.com/refer.com/redroid.com/reference./android.com/referenc./redroid/reference/referferenc./androidx/androidx/lifecycle/lifecycle/savedstate，state-.---/-/-/-/
这似乎是通过导航论证传递的一种非常好的技术，但是由于我在任何地方都没有考虑过渡到另一种技术。
In Android Compose navigation, navigation arguments are populated in SavedStateHandle which can then be accessed in a ViewModel. I have done this in practice and implementation is well outlined here: https://stackoverflow.com/a/69145748/12385518.
My problem is I cannot find any documentation on why/how this is happening. In fact I cannot even find official documentation that even mention navigation arguments being in SavedStateHandle at all. I would love to read more about this. I have read these documents (and more) but found nothing on the topic:
https://developer.android.com/topic/libraries/architecture/viewmodel-savedstate
https://developer.android.com/reference/androidx/lifecycle/SavedStateHandled
It seems to be a very nice technique for passing around navigation arguments, however since it isn't mentioned anywhere I am considering transitioning to another technique.
发布评论
评论（1）
这是将导航参数传递给
viewModel的方式。呼叫
navcontroller.navigate（route，args）anavbackstackentry是创建的（）。navbackstackentry创建顾名思义，它是使用ViewModelssavedstatehandles创建navbackStackentry实现hasdefaultViewModelProviderFactory，并通过default> defaultviewModelProviderFactoryproperty从上一步公开其工厂.android.com/androidx/platform/frameworks/support/+/androidx-main:navigation/navigation-common/src/main/java/androidx/navigation/NavBackStackEntry.kt;l=218?q=NavBackStackEntry&ss=androidx “ rel =“ noreferrer”>源）。至关重要的是，
HASDEFAULTVIEWMODELPROVIDERFACTORY还具有另一个属性：defaultViewModeLcreationExtras。这包含构建ViewModel时使用的额外数据字段。导航参数存储在此处（ source ）。当
viewModel创建方法（例如hiltviewModel）被调用，它将检查是否view> viewmodelstoreowner（在这种情况下，> navbackstackentry）实现HASDEFAULTVIEWMODELPROVIDERFACTORY。如果是这样，那么它将将那些额外的（导航参数）传递到视图模型工厂（视图模型工厂，在这种情况下
savedStateViewModeFactory，然后创建savedStateHandle，将其填充使用导航参数（Extras），并将其提供给新创建的新创建viewModel因此它具有访问权限（Here's how navigation arguments are passed to a
ViewModel.When you call
NavController.navigate(route, args)aNavBackStackEntryis created (source).NavBackStackEntrycreates aSavedStateViewModelFactorywhich, as its name suggests, is a factory for creatingViewModels with aSavedStateHandle(source).NavBackStackEntryimplementsHasDefaultViewModelProviderFactoryand exposes its factory from the previous step via thedefaultViewModelProviderFactoryproperty (source).Crucially,
HasDefaultViewModelProviderFactoryalso has another property:defaultViewModelCreationExtras. This contains extra data fields which are used when constructing aViewModel. The navigation arguments are stored here (source).When a
viewModelcreation method, such ashiltViewModel, is called it will check whether theViewModelStoreOwner(in this case theNavBackStackEntry) implementsHasDefaultViewModelProviderFactory. If it does, then it'll pass those extras (the navigation arguments) to the view model factory (source).The view model factory, in this case
SavedStateViewModelFactory, then creates theSavedStateHandle, populates it with the navigation arguments (the extras), and supplies it to a newly createdViewModelso it has access to them (source).