/ ViewPager

An extension for android ViewModel

An extension for android ViewModel

Vita

Vita is a light and simple library that helps you to share ViewModel between fragments and activities, even you can create ViewModels in application scope.

As we know we need a LifeCycleOwner (e.g Fragment or FragmentActivity) to create ViewModels, when the owner is at the end of its lifecycle the ViewModel will be cleared as well, Sometimes you need to share the ViewModel between multiple owners, By default we can only share ViewModel of an activity between its fragments for now, nothing more.

What Vita does:

  • Creates ViewModels with Single Owner:
    This is the default ViewModel behavior that already has, The ViewModels created in this way are only available to the owner.

single_owner_diagram

  • Creates ViewModels with Multiple Owners:
    The ViewModels are shared between multiple owners and stay alive while at least one owner is alive

multiple_owner_diagram

  • Creates ViewModels with No Owner:
    The ViewModels have no owner, they are available in the application scope and stay alive until the user closes the application

no_owner_diagram

Gradle setup

Make sure your project includes jcenter in its repositories and add this to build.gradle in app module

dependencies {
        implementation 'com.androidisland.arch:vita:0.1.0'
}

How to use

First start Vita in application class:

class App : Application() {
    override fun onCreate() {
    	super.onCreate()
	startVita()
	}
}

There is an extension value named vita that gives you access to a singleton object of Vita everywhere, Just pass your desired VitaOwner and get the ViewModel you want:

val myViewModel = vita.with(VitaOwner.Multiple(this)).getViewModel<MyViewModel>()

Also you can pass a function as factory like this:

val myViewModelWithFactory = vita.with(VitaOwner.Multiple(this)).getViewModel(){ MyViewModelWithFactory(initData) }

GitHub