如何将逻辑提取到 viewModel？

Question

In my fragment I have next code:

etAuthorName.doAfterTextChanged {
    viewModel.quoteAuthor.value = it?.toString()
}

viewModel.quoteAuthor.observe(this, Observer<String> {
    if (etAuthorName.text.toString() != it) {
        etAuthorName.setText(it)
    }
})

How i can extract this logic: if (etAuthorName.text.toString() != it) to my viewModel?

Answer 1

You can use databinding in this case, learn more here: https://developer.android.com/topic/libraries/data-binding

Edit: You can try something like this:

In your ViewModel class:

@get:Bindable
var bindetAuthorName: String = ""
    set(value) {
        field = value
        notifyPropertyChanged(BR.bindetAuthorName)
    }
    get() = field

fun comparison(){
    if(bindetAuthorName != quoteAuthor){
        bindetAuthorName = quoteAuthor
    }
}

in your xml edittext/ textview:

<Edittext
 .....
 android:text="@={viewModel.bindetAuthorName}"/>

and whenever your quoteAuthor value is updating you can call comparison(). I hope this helps!

Answer 2

You can use Transformations.distinctUntilChanged add this inside viewmodel and listen inside your fragment instead observer quoteAuthor

val authorDistinct = Transformations.distinctUntilChanged(quoteAuthor)

Answer 3

In order to really move your logic to ViewModel

You can change it to this

Fragment

etAuthorName.doAfterTextChanged {
    viewModel.triggerQuoteAuthor(etAuthorName.text.toString(), it?.toString())
}

viewModel.quoteAuthor.observe(this, Observer<String> {
    etAuthorName.setText(it)
})

ViewModel

fun triggerQuoteAuthor(beforeText: String, afterText: String) {
   if (beforeText != afterText) {
      quoteAuthor.value = afterText
   }
}