Android Databinding TextEdit Validation of two or more fields enable button - validation

Question

I am working on my first Android application using MVVM and Databinding. Some areas I am grasping but this one I am struggling with. The scenario:
I have a Create Account wizard activity, which uses Android Navigation Architecture to page through several fragments asking for input from the user. The first fragment/step asks the user for the first and last name. I do not want the button to proceed to the next step to enable until something is entered in both fields. I have enabled buttons based on ONE fields validation before, but not two. I feel like I am missing something silly.
Here is the button I want to enable after both fields have data in them:
<Button
android:id="#+id/continueToSecondStepButton"
android:layout_width="300dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="32dp"
android:background="#drawable/button_transparent_background"
android:onClick="#{() -> viewModel.proceedToNextStep()}"
android:text="#string/step_proceed"
android:enabled="#{safeUnbox(viewModel.firstNamesValid) && safeUnbox(viewModel.lastNamesValid)}"
android:textAllCaps="false"
android:textColor="#{safeUnbox(viewModel.firstNamesValid) && safeUnbox(viewModel.lastNamesValid) ? #colorStateList/white : #colorStateList/transparent_white}"
android:textSize="18sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/subtext" />
Primarily here the focus is:
android:enabled="#{safeUnbox(viewModel.firstNamesValid) && safeUnbox(viewModel.lastNamesValid)}"
android:textColor="#{safeUnbox(viewModel.firstNamesValid) && safeUnbox(viewModel.lastNamesValid) ? #colorStateList/white : #colorStateList/transparent_white}"
I have two Transformations to listen to key changes on the first and last name fields and execute the validation method:
firstNamesValid = Transformations.switchMap(firstName) { firstName -> isNamesValid() }
lastNamesValid = Transformations.switchMap(lastName) { lastName -> isNamesValid() }
and for now, just a simple method to check if both fields have data in them:
private fun isNamesValid(): LiveData<Boolean> {
var namesValid = false
if (!firstName.value.isNullOrEmpty() && !lastName.value.isNullOrEmpty()) {
namesValid = true
}
val mediatorLiveData: MediatorLiveData<Boolean> = MediatorLiveData()
mediatorLiveData.value = namesValid
return mediatorLiveData
}
It "kind of" works but not well. Can you enable a button based on validating two fields with Databinding? I have a feeling there is an easier way to do this. What happens with this setup is that, you fill out first and last name, and nothing happens, but if you then navigate back to the first name and enter another character it works and enables the button. I assume this is due to some logic error in my code. Thanks for looking.

Answer 1

I ended up figuring it out right after. Typing it up helped me find the issue and I will share what I did for others. I had a logic error in my code referencing the isNamesValid function.
I made the following changes:
isNamesValid now takes a string parameter and checks the specific string rather then hardcoded checking the first and last name values
private fun isNameValid(name: String?): LiveData<Boolean> {
var namesValid = false
if (!name.isNullOrEmpty()) {
namesValid = true
}
val mediatorLiveData: MediatorLiveData<Boolean> = MediatorLiveData()
mediatorLiveData.value = namesValid
return mediatorLiveData
}
Updated Transformations to call that method passing in the name to be checked.
firstNamesValid = Transformations.switchMap(firstName) { firstName -> isNameValid(firstName) }
lastNamesValid = Transformations.switchMap(lastName) { lastName -> isNameValid(lastName) }