如何在分页列表回收器视图的第一项更改时获得通知

Question

I'm using paging 3 to paginate my retrieved data. I want to show a badge on the bottom navigation bar when a new item has been added to the recycler view. imagine the user is watching recycler view in the situation below:

item A
item B
item C

now the user refresh the page using a swipe refreshing button which calls this function:

 binding.refresh.setOnRefreshListener {
            adapter.refresh()
    }

and a new item is added, so the situation would be like this:

item D
item A
item B
item C

the new data would be propagated using this line of code:

   viewModel.tickets.observe(viewLifecycleOwner, {
        viewLifecycleOwner.lifecycleScope.launch {
            adapter.submitData(it)
        }
   })

I want to show a badge at this moment. so I added an interface into my recycler paged list adapter like this:

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        ticketUtils.hasNewItem(getItem(0)?.ticket_id)
        holder.bind(getItem(position))
    }

which checks what is the first item of the recycler view. so I have implemented the body of this interface inside of my fragment like this:

    override fun hasNewItem(itemID: String?) {
        if (itemID.isNullOrEmpty())
            return
        if (itemID != firstTicketID)
            MainActivity.mainUtils.newTicket(showBadge = true)
    }

and MainActivity.mainUtils.newTicket is an interface that shows a badge on the desired icon.

but I have faced to the problem that it seems the recycler view won't be notified for new data till the user start scrolling. I mean the code written in onBindedViewHolder would be called just when the user scrolls the page. how can I solve that?

Answer 1

viewModel.tickets.observe(viewLifecycleOwner, {
//Here you get to know that there's update in your Datalist
    adapter.submitData(it)
})

When you insert a new data into the database, observe the data inserted by returning the id of the data. For example if you are using Room, it can return a long value, which is the new rowId for the inserted item. Compare with existing ones and then you can show a badge if there's new data in the list.