RecyclerView Data Binding

recyclerview-databinding.kt

open class DataBoundAdapter<T>(val lifecycleOwner: LifecycleOwner, val itemLayoutIdProvider: (T) -> Int, val bindingVariableId: Int, diffCallback: DiffUtil.ItemCallback<T>) : ListAdapter<T, DataBoundViewHolder>(diffCallback) {
	constructor(lifecycleOwner: LifecycleOwner, @LayoutRes itemLayoutId: Int, bindingVariableId: Int, diffCallback: DiffUtil.ItemCallback<T>) : this(lifecycleOwner, { itemLayoutId }, bindingVariableId, diffCallback)

	private val extras = hashMapOf<Int, Any>()

	override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DataBoundViewHolder {
		val layoutInflater = LayoutInflater.from(parent.context)
		val binding = DataBindingUtil.inflate<ViewDataBinding>(layoutInflater, viewType, parent, false)
		binding.setLifecycleOwner(lifecycleOwner)
		return DataBoundViewHolder(binding)
	}

	override fun getItemViewType(position: Int) = itemLayoutIdProvider.invoke(getItem(position))

	override fun onBindViewHolder(holder: DataBoundViewHolder, position: Int) {
		holder.binding.setVariable(bindingVariableId, getItem(position))
		extras.forEach { (varId, extra) -> holder.binding.setVariable(varId, extra) }
		holder.binding.executePendingBindings()
	}

	fun bindExtra(bindingVariableId: Int, extra: Any) = this.also {
		extras.put(bindingVariableId, extra)
	}
}

class DataBoundViewHolder constructor(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root)

@BindingAdapter("app:adapter", "app:items", requireAll = false)
fun <T> RecyclerView.setDataBoundAdapter(adapter: DataBoundAdapter<T>?, items: List<T>?) {
	if (this.adapter == null)
		this.adapter = adapter
	(this.adapter as DataBoundAdapter<T>).submitList(items)
}