具有给定密钥的 SavedStateProvider 已注册

Question

我目前正在试用带有 savedState 的新 Jetpack ViewModel。

    implementation 'androidx.lifecycle:lifecycle-viewmodel-savedstate:1.0.0-rc01'

我正在使用 1 Activity 并尝试与 2 个片段共享 1 个 ViewModel，但是当我尝试启动第二个片段时，我从标题中得到了错误。

这就是我使用 savedInstance 调用 ViewModel 的方式：

    val repository = (activity?.application as App).getRepository()
    viewModel = activity?.run {
        ViewModelFactory(repository, this, savedInstanceState).create(MainViewModel::class.java)
    } ?: throw Exception("Invalid Activity")

这是我的日志：

java.lang.IllegalArgumentException: SavedStateProvider with the given key is already registered
    at androidx.savedstate.SavedStateRegistry.registerSavedStateProvider(SavedStateRegistry.java:111)
    at androidx.lifecycle.SavedStateHandleController.attachToLifecycle(SavedStateHandleController.java:50)
    at androidx.lifecycle.SavedStateHandleController.create(SavedStateHandleController.java:70)
    at androidx.lifecycle.AbstractSavedStateViewModelFactory.create(AbstractSavedStateViewModelFactory.java:67)
    at androidx.lifecycle.AbstractSavedStateViewModelFactory.create(AbstractSavedStateViewModelFactory.java:84)
    at com.xxx.yyy.presentation.details.DetailsFragment.onCreate(DetailsFragment.kt:29)
    at androidx.fragment.app.Fragment.performCreate(Fragment.java:2586)
    at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:838)
    at androidx.fragment.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1197)
    at androidx.fragment.app.FragmentTransition.calculateFragments(FragmentTransition.java:1080)
    at androidx.fragment.app.FragmentTransition.startTransitions(FragmentTransition.java:119)
    at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1866)
    at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
    at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
    at androidx.fragment.app.FragmentManagerImpl.run(FragmentManagerImpl.java:150)

它似乎在尝试使用已注册的 SavedState，因此出现错误？我认为这就是图书馆的全部意义所在。任何人都可以帮助或指出如何使用此传递参数到 ViewModel 并使用 savedStateHandle 吗？

Answer 1

您永远不应该自己调用 create - 这样，您实际上并没有使用已经创建的保留 ViewModel，导致 AbstractSavedStateViewModelFactory 尝试注册同一个键不止一次。

相反，您应该将 ViewModelFactory 传递给 ViewModelProvider 实例以检索已经存在的 ViewModel 或仅在必要时创建它：

val repository = (activity?.application as App).getRepository()
viewModel = activity?.run {
    val factory = ViewModelFactory(repository, this, savedInstanceState)
    ViewModelProvider(this, factory).get(MainViewModel::class.java)
} ?: throw Exception("Invalid Activity")

如果您依赖 fragment-ktx 版本 1.1.0 或更高版本，您可以改为使用 by activityViewModels Kotlin 属性委托，它懒惰地使用 ViewModelProvider引擎盖下：

val viewModel: MainViewModel by activityViewModels {
    val repository = (activity?.application as App).getRepository()
    ViewModelFactory(repository, requireActivity(), savedInstanceState)
}

具有给定密钥的 SavedStateProvider 已注册

SavedStateProvider with the given key is already registered

android

android-fragments

android-viewmodel

android-jetpack

androidx