Kotlin - RecyclerView.ViewHolder subclass - unable to access an extra property

Question

I have implemented RecyclerView.ViewHolder sub-class as below:

class PersonViewHolder(itemView: View, binding: ViewDataBinding) : RecyclerView.ViewHolder(itemView) { }

Now I am trying to access binding property declared in it like this within subclass of RecyclerView.Adapter:

override fun onBindViewHolder(holder: PersonViewHolder?, position: Int) {
        val person = persons[position]

        if (holder != null) {
            holder.binding.setVariable(BR.person, person) // line with error
            holder.binding.executePendingBindings() // line with error
        }
    }

But compiler is complaining - Unresolved reference: binding

Here is the complete implementation:

class PersonsAdapter(private var persons: Array<Person>) : RecyclerView.Adapter<PersonsAdapter.PersonViewHolder>() {
    override fun onBindViewHolder(holder: PersonViewHolder?, position: Int) {
        val person = persons[position]

        if (holder != null) {
            holder.binding.setVariable(BR.person, person)
            holder.binding.executePendingBindings()
        }
    }

    override fun getItemCount(): Int {
        return persons.size
    }

    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): PersonViewHolder {
        val itemView = LayoutInflater.from(parent!!.context).inflate(R.layout.list_item_person, parent, false)
        return PersonViewHolder(itemView, DataBindingUtil.bind(itemView))
    }

    class PersonViewHolder(itemView: View, binding: ViewDataBinding) : RecyclerView.ViewHolder(itemView) { }
}

Any ideas if I am missing anything over here? Please suggest.

Answer 1

binding: ViewDataBinding - you're only defining a constructor parameter, it is never saved as a member of the class. Mark it using var or val to have it store the parameter and have it be accessible later on.

Answer 2

check build.gradle file (module level) in your project

in the top android extesion plugin is included or not? plugin { id 'kotlin-android-extensions' }