如何在Android SunFlower 项目的Activity 中获取ViewModel？

Question

I am studying MVVM of Google Android SunFlower project.

For Fragment , it gets viewmodel like the following

private val plantDetailViewModel: PlantDetailViewModel by viewModels {
        InjectorUtils.providePlantDetailViewModelFactory(requireActivity(), args.plantId)
    }

I want to try the same method to get viewmodel in Activity. but the requireActivity() show unresolved reference...

And the data binding is not working when I replace it to this .

Does it has other pattern can be use for providePlantDetailViewModelFactory()

Thanks in advance.

Answer 1

You have to add these to your build.gradle

implementation "androidx.core:core-ktx:1.3.1"
implementation "androidx.fragment:fragment-ktx:1.2.5"

Usage in Activity

val usersViewModel: UsersViewModel by viewModels()

Usage in Fragment

// Get a reference to the ViewModel scoped to this Fragment
val viewModel by viewModels<MyViewModel>()

// Get a reference to the ViewModel scoped to its Activity
val viewModel by activityViewModels<MyViewModel>()

Answer 2

You need a gradle dependency on "androidx.activity:activity-ktx:$version" .

Then you can import androidx.activity.viewModels in your Activity.

Answer 3

I don't think so that you can do similar for your Activity that's done for Fragment .

Why?

The delegate function viewModels is available from fragment-ktx library (Refer here for reference ) as extension for getting ViewModel instance lazily on your value objects using by keyword.

And there's no such thing available for Activities , for an instance.

So, better is to create your own or find some other way like basic lazy{} function from Kotlin standard library and providing logic to it.