Xamarin Android endless scroll of recycleview scrolls to top - xamarin

Question

I have an requirement where the user should be able to load more data when the end of recycleview has reached,something like lazy loading.I am able to implement this functionality with the help of this link ,but everytime I reach the bottom and load more data the recycleview item starts from top and I Have to scroll to bottom to view the items.
Here is my code:
private async void DisplayCurrentYearData()
{
//current year
try
{
if (oStaticVariables.bIsConnected == true)
{
CurrentYear.StartIndex = 1;
CurrentYear.EndIndex = 20;
var oActCurYrData = await oWebApiService.GetCurrentYearList(oStaticVariables.MembershipID);
//var oActCurYrData = await oWebApiService.GetMembersLastYearData(new Commom.Files.Models.Member() { MembershipID = Convert.ToInt32(oStaticVariables.MembershipID) });
if (oActCurYrData != null && oActCurYrData.Count != 0)
{
this.listItems = new List<DataType>();
foreach (Commom.Files.Models.YearlyData x in oActCurYrData.ToList())
{
LogbookGroupData g1 = new LogbookGroupData(x.EventDescription, x.ActivityDescription);
if (x.Status == "1")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Submitted");
g1.items.Add(e11);
}
else if (x.Status == "2")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Awarded");
g1.items.Add(e11);
}
else if (x.Status == "3")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Declined");
g1.items.Add(e11);
}
else
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Forwarded To Vetting Team");
g1.items.Add(e11);
}
listItems.Add(g1);
}
oStaticVariables.MyActivityYearlyData = oActCurYrData;
if (Activity != null)
{
this.recyclerAdapterCY = new LogbookCurrentYearRecycleViewAdaptor(Activity, listItems);
this.recyclerAdapterCY.GroupClickCurrent += OnGroupClickCurrent;
this.mLayoutManager = new LinearLayoutManager(Activity);
var onScrollListener = new RecyclerViewOnScrollListenerCY(this.mLayoutManager);
onScrollListener.LoadMoreEvent += (object sender, EventArgs e) =>
{
//Load more stuff here
LoadMoreCurrentYearData();
};
recyclerViewCY.AddOnScrollListener(onScrollListener);
this.recyclerViewCY.SetLayoutManager(mLayoutManager);
this.recyclerViewCY.SetAdapter(recyclerAdapterCY);
}
}
else {
}
}
}
catch (Exception ex)
{
}
}
private async void LoadMoreCurrentYearData()
{
CurrentYear.IsLoading = true;
CurrentYear.StartIndex = CurrentYear.EndIndex + 1;
CurrentYear.EndIndex = CurrentYear.EndIndex + 5;
//current year
try
{
txtTotalPoints.Visibility = ViewStates.Gone;
if (oStaticVariables.bIsConnected == true)
{
ShowSpinner();
var oActCurYrData = await oWebApiService.GetCurrentYearList(oStaticVariables.MembershipID);
//var oActCurYrData = await oWebApiService.GetMembersLastYearData(new Commom.Files.Models.Member() { MembershipID = Convert.ToInt32(oStaticVariables.MembershipID) });
if (oActCurYrData != null && oActCurYrData.Count != 0)
{
this.listItemsNew = new List<DataType>();
foreach (Commom.Files.Models.YearlyData x in oActCurYrData.ToList())
{
LogbookGroupData g1 = new LogbookGroupData(x.EventDescription, x.ActivityDescription);
if (x.Status == "1")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Submitted");
g1.items.Add(e11);
}
else if (x.Status == "2")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Awarded");
g1.items.Add(e11);
}
else if (x.Status == "3")
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Declined");
g1.items.Add(e11);
}
else
{
LogbookEntryData e11 = new LogbookEntryData(x.FormattedDate, x.Points, "Forwarded To Vetting Team");
g1.items.Add(e11);
}
listItemsNew.Add(g1);
}
listItems.AddRange(listItemsNew);
//oStaticVariables.MyActivityYearlyData = oActCurYrData;
if (Activity != null)
{
this.recyclerAdapterCY = new LogbookCurrentYearRecycleViewAdaptor(Activity, listItems);
this.recyclerAdapterCY.GroupClickCurrent += OnGroupClickCurrent;
this.recyclerViewCY.SetAdapter(recyclerAdapterCY);
HideSpinner();
CurrentYear.IsLoading = false;
}
}
else
{
HideSpinner();
CurrentYear.IsLoading = false;
}
}
}
catch (Exception ex)
{
}
}
Here is my RecyclerViewOnScrollListenerCY class:
public class RecyclerViewOnScrollListenerCY : RecyclerView.OnScrollListener
{
public delegate void LoadMoreEventHandler(object sender, EventArgs e);
public event LoadMoreEventHandler LoadMoreEvent;
private LinearLayoutManager LayoutManager;
public RecyclerViewOnScrollListenerCY(LinearLayoutManager layoutManager)
{
LayoutManager = layoutManager;
}
public override void OnScrolled(RecyclerView recyclerView, int dx, int dy)
{
base.OnScrolled(recyclerView, dx, dy);
var visibleItemCount = recyclerView.ChildCount;
var totalItemCount = recyclerView.GetAdapter().ItemCount;
var pastVisiblesItems = LayoutManager.FindFirstVisibleItemPosition();
if ((visibleItemCount + pastVisiblesItems) >= totalItemCount && !CurrentYear.IsLoading)
{
LoadMoreEvent(this, null);
}
}
}
Can somebody point out my mistake in the code.Please help

Answer 1

According to your description, you want to scroll and not reset position to the top for recycleview every time.
Originally I was creating a new Adapter when the data changed. The adapter base class will automatically clear the contents of the data calling .Clear(). This causes the scroll view to go to the top each time.
To avoid the .Clear() you need to not create a new instance of the adapter and just call Adapter.NotifyDataSetChanged() and the scroll view will not refresh to top every time data refreshes.
https://developer.xamarin.com/api/member/Android.Widget.BaseAdapter.NotifyDataSetChanged/