xamarin - Xamarin Android 无限滚动 recycleview 滚动到顶部

Question

我有一个要求，当 recycleview 结束时，用户应该能够加载更多数据，比如延迟加载。我可以在这个链接的帮助下实现这个功能，但是每次我到达底部并加载更多数据 recycleview 项目从顶部开始，我必须滚动到底部才能查看项目。这是我的代码：

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)
        {

        }
    }

这是我的 RecyclerViewOnScrollListenerCY 类：

 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);
        }
    }
}

有人可以指出我在代码中的错误吗？请帮忙

标签： xamarinandroid-recyclerviewxamarin.android

Answer 1

根据您的描述，您每次都希望滚动而不是将位置重置到顶部以进行循环查看。

最初，当数据更改时，我正在创建一个新的适配器。适配器基类会自动清除调用.Clear() 的数据内容。这会导致滚动视图每次都转到顶部。

为了避免 .Clear() 您不需要创建适配器的新实例，只需调用 Adapter.NotifyDataSetChanged() 并且每次数据刷新时滚动视图都不会刷新到顶部。

https://developer.xamarin.com/api/member/Android.Widget.BaseAdapter.NotifyDataSetChanged/