Kotlin RecyclerView not updating after data changes - kotlin

Question

I am using RecyclerView to display a dynamic list of data and after I call an api I need to update my RecyclerView UI but the items in my RecyclerView does not change...
Below is my how I init my RecyclerView in my Fragment:-
forwardedList.layoutManager = LinearLayoutManager(context!!, RecyclerView.VERTICAL, false)
adapter = ForwardListAdapter(SmsHelper.getForwardedSms(context!!))
forwardedList.adapter = adapter
Below is my custom RecyclerView Adapter:-
class ForwardListAdapter(val forwardedList: List<SmsData>) : RecyclerView.Adapter<ForwardListAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ForwardListAdapter.ViewHolder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.forwarded_item, parent, false)
return ViewHolder(v)
}
override fun onBindViewHolder(holder: ForwardListAdapter.ViewHolder, position: Int) {
holder.bindItems(forwardedList[position])
}
override fun getItemCount(): Int {
return forwardedList.size
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
fun bindItems(sms: SmsData) {
val simSlotText: TextView = itemView.findViewById(R.id.simSlot)
val senderText: TextView = itemView.findViewById(R.id.sender)
simSlotText.text = "[SIM ${sms.simSlot}] "
senderText.text = sms.sender
}
}
}
I am currently updating my RecyclerView from SmsHelper class as below:-
val fragments = mainActivity!!.supportFragmentManager.fragments
for (f in fragments) {
if (f.isVisible) {
if (f.javaClass.simpleName.equals("ForwardedFragment")) {
val fg = f as ForwardedFragment
fg.adapter.notifyDataSetChanged() <----- HERE
} else if (f.javaClass.simpleName.equals("FailedFragment")) {
val fg = f as FailedFragment
fg.adapter.notifyDataSetChanged()
}
}
}

Answer 1

As I observed, you did not really change the adapter's data but only called notifyDataSetChanged. You cannot just expect the data to be changed automatically like that since notifyDataSetChanged only:
Notifies the attached observers that the underlying data has been changed and any View reflecting the data set should refresh itself.
You need to change the data by yourself first, then call notifyDataSetChanged.
class ForwardListAdapter(private val forwardedList: MutableList<SmsData>) : RecyclerView.Adapter<ForwardListAdapter.ViewHolder>() {
// ...
fun setData(data: List<SmsData>) {
forwardedList.run {
clear()
addAll(data)
}
}
// ...
}
Then do it like this:
adapter.run {
setData(...) // Set the new data
notifyDataSetChanged(); // notify changed
}