How can I iterate over all views known to the data binder?

Question

I have three TextInputEditText views in my layout where the user can type in specific information.
On the click of a Button this information is stored in my database.

After the user clicks this Button, I want to clear all TextInputEditText fields.
Right now, I am doing this by hardcoding:

private fun clearAllEditTextFields() {
        
    Timber.d("clearAllEditTextFields: called")
        
    binding.bookTitleEditText.text = null
    binding.bookAuthorEditText.text = null
    binding.bookPageCountEditText.text = null
        
}

Since this is bad, I would like to use a dynamic for each loop to identify all views of type TextInputEditText known to binding and clear their content:

private fun clearAllEditTextFields() {
        
    Timber.d("clearAllEditTextFields: called")
        
    for (view in binding.views) {

        if (view is TextInputEditText) {

            view.text = null
        
        }

}

Unfortunately, there is no such field binding.views.
Is there still a way to achieve this or something with the same properties?

What I have tried so far

I have used a BindingAdapter. In my Util class, where all my extension functions go, I have created an EditText extension function clearText annotated as BindingAdapter and JvmStatic:

@JvmStatic
@BindingAdapter("clearText")
fun EditText.clearText(@NotNull shouldClear: Boolean) {
        
    Timber.d("clearText: called")
        
    if (shouldClear) text = null
        
}

In XML:

<com.google.android.material.textfield.TextInputEditText
    android:id="@+id/book_title_edit_text"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:imeActionId="100"
    android:imeOptions="actionNext"
    android:inputType="text"
    android:text="@={viewModel.bookTitle}"
    app:clearText="@{viewModel.clearAllEditTextFields}"
/>

In my ViewModel class, I have created a var clearAllEditTextFields = false which is modified in the clearAllEditTextFields() function which gets called inside my ViewModel:

...
var clearAllEditTextFields = false
clearAllEditTextFields()
...

private fun clearAllEditTextFields() {
        
    Timber.d("clearAllEditTextFields: called")
        
    clearAllEditTextFields = true
        
}

According to Logcat, my extension function is called when my ViewModel is initialized. However, when clearAllEditTextFields() gets called, it does not trigger a new call to the extension function.

Answer 1

A simple for loop doesn't exist to loop over the views in the binding object and you can try the following to keep your code conscice.

Scope Functions

    binding.apply{
       bookTitleEditText.text = null
       bookAuthorEditText.text = null
       bookPageCountEditText.text = null
    }

scope functions are a good go iff there are few views and we end up with quite a boiler-plate code if the number of views is large, in which cases I think Binding-Adapter would be a good choice

@BindingAdapter("clear_text")
fun EditText.clearText(shouldClear : Boolean?){
   shouldClear?.apply{
       if(shouldClear)
          text = null
   }
}

ViewModel

private val _shouldClear = MutableLiveData<Boolean>()
val shouldClear : LiveData<Boolean>
get() = _shouldClear

fun setClearStatus(status : Boolean){
   _shouldClear.value = status
}

//since clearing a text is an event and not state, reset the clear_status once it's done
fun resetClearStatus(){
  _shouldClear.value = nul
}

XML

<EditText 
  ......
  app:clear_text = "@{yourViewModel.shouldClear}"
  ...... />

ActivityClass

...
binding.lifecycleOwner = this
...


private fun clearAllEditTextFields() {
   yourViewModel.setClearStatus(true)
   yourViewModel.resetClearStatus()        
}

Edit:

add binding.lifecycleOwner = this in your activity class and its used for observing LiveData with data binding. The view will observe for text changes at runtime.