创建视图模型时需要传递值（userData），因此我需要创建视图模型工厂
这是我的viewModel，我需要application和userData来初始化此ScoreViewModel
class ScoreViewModel(application: Application, userData: UserKM) : AndroidViewModel(application) {
}
但是现在我在创建viewModel工厂时困惑如何传递application
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")
}
}
我该怎么办？
您可以有这样的东西：
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")
}
}
您的活动或片段中有：
/**
* 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)
}
这里您的viewModel可能看起来像：
class NewsViewModel(application: Application) : AndroidViewModel(application)