我需要在创建 View 模型时传递值(userData),所以我需要创建一个 View 模型工厂
这是我的viewModel,我需要application
和 userData
初始化 ScoreViewModel
class ScoreViewModel(application: Application, userData: UserKM) : AndroidViewModel(application) {
}
但现在我很困惑如何通过
application
当我创建 viewModel 工厂时class ScoreViewModelFactory(private val userData: UserKM) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(ScoreViewModel::class.java)) {
return ScoreViewModel(userData = userData,application = ?????? ) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
我应该怎么办 ?
最佳答案
你可以有这样的东西:
class Factory(val app: Application) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(NewsViewModel::class.java)) {
@Suppress("UNCHECKED_CAST")
return NewsViewModel(app) as T
}
throw IllegalArgumentException("Unable to construct viewmodel")
}
}
在您的 Activity 或 fragment 中,您有:
/**
* One way to delay creation of the viewModel until an appropriate lifecycle method is to use
* lazy. This requires that viewModel not be referenced before onActivityCreated, which we
* do in this Fragment.
*/
private val viewModel: NewsViewModel by lazy {
val activity = requireNotNull(this.activity) {
"You can only access the viewModel after onActivityCreated()"
}
ViewModelProviders.of(this, NewsViewModel.Factory(activity.application))
.get(NewsViewModel::class.java)
}
在这里,您的 viewModel 可能如下所示:
class NewsViewModel(application: Application) : AndroidViewModel(application)
有关更多详细信息,您可以查看:https://github.com/Ali-Rezaei/News-Cache/blob/master/app/src/main/java/com/sample/android/news/viewmodels/NewsViewModel.kt
关于android - 如何为 AndroidViewModel 创建 View 模型工厂?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60786299/