I have a home page containing a RecyclerView as well as an "Add Show" button which redirects me to a form in order to add a show to the recyclerView.

My goal is, when the page to add a show closes, to have the newly added show displayed in my recyclerView. However, that only happens about half the times, which obviously isn't what I want. I've tried using a ValueEventListener in my adapter, but besides looking like a bad idea, it doesn't even work.

I've also tried using notifyItemInserted but I don't know how I should implement it, as my AddShowActivity doesn't have any link with the adapter. So right now I don't have any idea left and that's why I'm here.

Both my AddShowActivity and my adapter are called from my HomeFragment:

class HomeFragment(private val context: MainActivity) : Fragment() {
    private lateinit var verticalRecyclerView: RecyclerView
    private lateinit var buttonAddShow: Button
    private lateinit var showsAdapter: ShowAdapter

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_home, container, false)

        setupComponents(view)
        initializeComponents()

        return view
    }

    private fun setupComponents(view: View) {
        verticalRecyclerView = view.findViewById(R.id.home_recycler_view)
        buttonAddShow = view.findViewById(R.id.home_button_add_show)
        showsAdapter = ShowAdapter(context, R.layout.item_show, null)
    }

    private fun initializeComponents() {
        verticalRecyclerView.adapter = showsAdapter

        swipeRefreshLayout.setOnRefreshListener{
            refreshFragment()
        }

        buttonAddShow.setOnClickListener{
            startActivity(Intent(context, AddShowActivity::class.java))
        }
    }
}

CodePudding user response：

the fast way is that.

1. assign the adapter to a public static var and you need to check if the var value is available or not before using
2. once any underlay data in the adapter is changed. call the adapter notifyDataSetChanged method to refresh the UI

CodePudding user response：

There are mutiple ways:

1. If you are willing to change AddShowActivity to Fragment, then you can use MVVM which contains your ShowList wrapped with an Observer pattern (ex: LiveData). When your list changes (for example: AddShow), the Adapter will be notified abt that and refresh itself:

viewModel.showList.observe(viewLifecycle) {
    showsAdapter.setData(it)
    notifyDataSetChanged()
}

On the other hand, if you not prefer MVVM, you can also register a FragmentResultListener, then manually update the RV here.

2. If there are 2 seperate Activities, I just wonder does it always fetch data each time Activity start/restart, so you kinda don't have to care about that?

CodePudding user response：

Basically, you want your list of shows to refresh when you add a new show. You can do that in the Fragment class by adding notifyDataSetChanged after you add new data to the list. However, Android studio gives a warning about how expensive the operation becomes.

notifyDataSetChanged sample

An easier solution to notifyDataSetChanged is using a DiffUtil. notifyDataSetChanged refreshes the whole list even if 99% of the list items remain unchanged which can cause a decrease in user experience as the list increases. DiffUtil fixes this by checking for items that have changed and updating only those items.

Adapter class

DiffUtil Class