What the actual meaning `Caused by: java.lang.RuntimeException: view must have a tag`?

Question

Please inform me if knowing whats tag that wanted.

Caused by: java.lang.RuntimeException: view must have a tag

__BaseActivity.java

Answer 1

I have used inflater without "attachToRoot". This error always occurs with issues related to inflater in adapter.

Answer 2

Another scenario where this error occurs is in a RecyclerView's ViewHolder.

Avoid initialising a binding instance in the ViewHolder's bind method

class BindingAdapter(private val items: List<Any>): RecyclerView.Adapter<BindingHolder>() {
      override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BindingHolder {}

      override fun onBindViewHolder(holder: BindingHolder, position: Int) {
           holder.bindItem(items[position])
      }
 }

class BindingHolder(view: View): RecyclerView.ViewHolder(view) {
    fun bindItem(item: Any) {
        //Don't do this
        val binding = ItemSampleBinding.bind(itemView)
    }
}

The databinding instance should be initialised outside the bind method because ViewHolders could be recycled and in the code above we could be trying to create a binding instance from a view that's already bound.

Instead create the binding instance in initialisation block of the ViewHolder (this can be in init{} block or just after the class declaration as shown below)

class BindingHolder(view: View): RecyclerView.ViewHolder(view) {
    val binding = ItemSampleBinding.bind(view)

    fun bindItem(item: Any) {
        //Rest of ViewHolder logic
        //binding.textView.text = "Something nice"
    }
}

Answer 3

Usually happens while learning about data binding in android, we usually use a main_activity.xml and then include content_main.xml but we by mistake put the <layout tag in content file. We need to put this <layout and <data tag in parent file that is used in setContentView()