android - ViewModelProviders 已过时，应该更换什么？

Question

我使用 ViewModelProviders。但是今天，更新库后，有30条消息。据我所知，ViewModelProviders 不再可用，您需要替换它，我查看了 developer.google，但不明白要替换什么？我的代码:

inline fun <reified T : ViewModel> FragmentActivity.injectViewModel(factory: ViewModelProvider.Factory): T {
    return ViewModelProviders.of(this, factory)[T::class.java]
}

inline fun <reified T : ViewModel> Fragment.injectViewModel(factory: ViewModelProvider.Factory): T {
    return ViewModelProviders.of(this, factory)[T::class.java]
}

你能解释一下为什么它已经过时了吗？

Answer 1

根据 the documentation :

Use the by viewModels() Kotlin property delegate or ViewModelProvider.ViewModelProvider(ViewModelStoreOwner, Factory), passing in the fragment and factory.

因此您可以将扩展替换为:

inline fun <reified T : ViewModel> FragmentActivity.injectViewModel(factory:  ViewModelProvider.Factory): T {
    return ViewModelProvider(this, factory)[T::class.java]
}

inline fun <reified T : ViewModel> Fragment.injectViewModel(factory: ViewModelProvider.Factory): T {
    return ViewModelProvider(this, factory)[T::class.java]
}

并且，根据错误消息，您可以改为使用 fragment-ktx 和 activity-ktx 依赖项中的 Kotlin 属性扩展，并完全删除您的扩展方法。

即 by viewModels和 by activityViewModels对于 fragment :

// Retrieve the ViewModel associated with this Fragment
val viewModel: MyVewModel by viewModels { myFactory }

// Retrieve the ViewModel associated with the activity
val activityViewModel: MyVewModel by activityViewModels { myFactory }

或者，如果您从 Activity 本身访问 ViewModel，您将使用它的 by viewModels :

// In an Activity, you can retrieve a ViewModel scoped to the Activity
// by using viewModels
val viewModel: MyVewModel by viewModels { myFactory }