Caution: A ViewModel must never reference a view, Lifecycle, or any class that may hold a reference to the activity context.
ameybhandarkar opened this issue · 6 comments
I am trying to implement MVVM in my current project. I was searching for some references. I just to clear a few doubts. So you can correct me if I am wrong.
mLoginViewModel.setNavigator(this);
This line of code is actually passing on the reference of the current activity to that viewmodel. But as per documentation, Caution: A ViewModel must never reference a view, Lifecycle, or any class that may hold a reference to the activity context.
So is there any alternative to this?
I am also searching for an approach of handling errors thrown by the API. I'd be glad if you can guide me through. Thanks
@ameybhandarkar the navigator is an interface between the activity and the viewmodel. That is not holding a reference to a context or really anything. There is a special kind of viewmodel called the AndroidViewModel that does hold reference to a context.
@clj0020 It holds a reference to the object that implements the interface, in this case the activity. There are better ways to notify the UI, try using Live Data.
@ameybhandarkar have idea for replace Weak references
in ViewModel i create
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data class Input( val name: Observable<String>, val image: Observable<ByteArray>, val triggerAdd: Observable<Unit> ) data class Output( val isAdd: Observable<Boolean> )
fun transform(input: Input): Output{
val nameImage = BehaviorSubject.create<String>()
val imageLibrary = BehaviorSubject.create<ByteArray>()
val isAdd = BehaviorSubject.create<Boolean>()
with(input){
name.subscribe(nameImage)
image.subscribe(imageLibrary)
triggerAdd.subscribe {
val name = nameImage.value ?:""
val image = imageLibrary.value ?: byteArrayOf()
dataManager.insert(Library(null,name,image))
.subscribeOn(schedulerProvider.io)
.observeOn(schedulerProvider.ui)
.subscribe ({
isAdd.onNext(it)
},{
Log.d("addImage",it.message)
})
}
}.addTo(compositeDisposable)
return Output(isAdd)
}
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in Activity/Fragment i create
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private fun bindViewModel(){ val output = viewModel.transform( RoomImageViewModel.Input( edImage.textChanges().map { it.toString() }, image, btnInsert.clicks().throttleFirst(300, TimeUnit.MILLISECONDS) ) ) with(output){ isAdd.subscribe { Log.d("AddImage",it.toString()) } isDelete.subscribe { Log.d("Delete",it.toString()) } } }
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@ameybhandarkar the navigator is an interface between the activity and the viewmodel. That is not holding a reference to a context or really anything. There is a special kind of viewmodel called the AndroidViewModel that does hold reference to an applictation context.
just corrected something 👍🏿