Styjun

I am implementing Two-Way DataBinding with Android Architecture Components using LiveData and ViewModel, but when I build the project it gives

error: cannot find symbol
import package.[layout_name]BindingImpl;

in DataBinderMapperImpl.java

I followed official documentation and looked at SO for answers but none of them had workable solutions.

already tried this one and this one

layout.xml

 <data>
 <import type="package.ViewModel" /> // this line was added from an answer but didn't work
 <variable
 name="model"
 type="package.ViewModel"/>
 </data>

// an input field I want to bind data with
<androidx.appcompat.widget.AppCompatAutoCompleteTextView
 android:id="@+id/email"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:text="@=model.email" // if I remove this line, builds fine
 android:hint="@string/prompt_email"
 android:inputType="textEmailAddress"
 android:maxLines="1"
 android:singleLine="true" />

Extending my ViewModel from AndroidViewModel instead of BaseObservable as mentioned in documentation

ViewModel.kt

 private val email: MutableLiveData<String> by lazy MutableLiveData<String>() 
 @Bindable // tried to change the return type to String, still no luck
 fun getEmail(): LiveData<String> 
 return email
 

 fun setEmail(email: String) 
 this.email.value = email
 

This is how I bind ViewModel with View

Activity.kt

binding.model = ViewModelProviders.of(this, ViewModelProvider.AndroidViewModelFactory
 .getInstance(application))
 .get(LoginViewModel::class.java)

What am I missing? Already included all things pre-databinding and if I had replaced ViewModel in layout with a data class and tried to get data from it, that works fine but with @ in layout

EDIT

Okay, so when I expose email as public, it compiles and binding works, but I can't make its setter and getter public, I mean when I try to expose it from its getter and setter, IDE says that these are already private functions and cannot be overriden?

How can I make this property expose through functions?

You can use getter of particular variable directly using get() method to variable (also works for setter too as set(value)) like below :

@get:Bindable // We make getter method bindable for data-binding
val email = MutableLiveData<String>()
 get() // Try to provide getter method like this
 return field as LiveData<String>
 
 set(data) // Try to provide setter method like this
 if(field.value != data.value) // To avoid infinite loop
 field.value = data.value
 

Found the answer on Reddit.

For two-way databinding to work, you have to expose your fields and they should be MutableLiveData like

val email = MutableLiveData<String>()

since kotlin already has get and set properties, they'll be used by Binding classes for fields