private View getStartView(RecyclerView.LayoutManager layoutManager, OrientationHelper helper)
{
var linearLayoutManager = (LinearLayoutManager)layoutManager;
var firstChildIndex = linearLayoutManager.FindFirstVisibleItemPosition();
if (firstChildIndex == RecyclerView.NoPosition)
{
return(null);
}
subject.OnNext(linearLayoutManager.FindFirstCompletelyVisibleItemPosition() + 1);
var lastItemIndex = linearLayoutManager.ItemCount - 1;
var isLastItem = linearLayoutManager.FindLastCompletelyVisibleItemPosition() == lastItemIndex;
if (isLastItem)
{
return(null);
}
var firstView = layoutManager.FindViewByPosition(firstChildIndex);
var decoratedEnd = helper.GetDecoratedEnd(firstView);
var threshold = helper.GetDecoratedMeasurement(firstView) / 2;
if (decoratedEnd >= threshold && decoratedEnd > 0)
{
return(firstView);
}
return(layoutManager.FindViewByPosition(firstChildIndex + 1));
}
public override void CollectAdjacentPrefetchPositions(int dx, int dy, RecyclerView.State state, ILayoutPrefetchRegistry layoutPrefetchRegistry)
{
try
{
base.CollectAdjacentPrefetchPositions(dx, dy, state, layoutPrefetchRegistry);
int delta = Orientation == Horizontal ? dx : dy;
if (ChildCount == 0 || delta == 0)
{
return;
}
int layoutDirection = delta > 0 ? 1 : -1;
View child = GetChildClosest(layoutDirection);
int currentPosition = GetPosition(child) + layoutDirection;
int scrollingOffset;
if (layoutDirection == 1)
{
scrollingOffset = MOrientationHelper.GetDecoratedEnd(child) - MOrientationHelper.EndAfterPadding;
for (int i = currentPosition + 1; i < currentPosition + MAdditionalAdjacentPrefetchItemCount + 1; i++)
{
if (i >= 0 && i < state.ItemCount)
{
layoutPrefetchRegistry.AddPosition(i, Java.Lang.Math.Max(0, scrollingOffset));
}
}
}
}
catch (Exception e)
{
Console.WriteLine(e);
}
}
public void AssignFromView(View referenceChild, int position)
{
Coordinate = LayoutFillingStartsFromEnd
? OrientationHelper.GetDecoratedEnd(referenceChild) + OrientationHelper.TotalSpaceChange
: OrientationHelper.GetDecoratedStart(referenceChild);
Position = position;
}
protected override int VisiblePortion(AView view, OrientationHelper orientationHelper, bool rtl)
{
if (rtl)
{
return(orientationHelper.TotalSpace - orientationHelper.GetDecoratedStart(view));
}
return(orientationHelper.GetDecoratedEnd(view));
}
private View GetStartView(
RecyclerView.LayoutManager layoutManager,
OrientationHelper helper,
out int viewPosition)
{
viewPosition = -1;
if (!(layoutManager is LinearLayoutManager manager))
{
return(base.FindSnapView(layoutManager));
}
int firstChild = manager.FindFirstVisibleItemPosition();
bool isLastItem = manager.FindLastCompletelyVisibleItemPosition() == layoutManager.ItemCount - 1;
if (isLastItem)
{
if (WeakNativeView.TryGetTarget(out var target))
{
target.CurrentSnapIndex = layoutManager.ItemCount - 1;
// System.Diagnostics.Debug.WriteLine($">>>>>> CurrentSnapIndex: {target.CurrentSnapIndex}");
}
return(null);
}
if (firstChild == RecyclerView.NoPosition)
{
return(null);
}
View child = layoutManager.FindViewByPosition(firstChild);
if (helper.GetDecoratedEnd(child) >= helper.GetDecoratedMeasurement(child) / 2 &&
helper.GetDecoratedEnd(child) > 0)
{
viewPosition = firstChild;
return(child);
}
viewPosition = firstChild + 1;
return(layoutManager.FindViewByPosition(firstChild + 1));
}
private View GetStartView(
RecyclerView.LayoutManager layoutManager,
OrientationHelper helper,
out int viewPosition)
{
viewPosition = -1;
if (!(layoutManager is LinearLayoutManager manager))
{
return(base.FindSnapView(layoutManager));
}
int firstChild = manager.FindFirstVisibleItemPosition();
bool isLastItem = manager.FindLastCompletelyVisibleItemPosition() == layoutManager.ItemCount - 1;
if (firstChild == RecyclerView.NoPosition || isLastItem)
{
return(null);
}
View child = layoutManager.FindViewByPosition(firstChild);
if (helper.GetDecoratedEnd(child) >= helper.GetDecoratedMeasurement(child) / 2 &&
helper.GetDecoratedEnd(child) > 0)
{
viewPosition = firstChild;
return(child);
}
if (manager.FindLastCompletelyVisibleItemPosition() == layoutManager.ItemCount - 1)
{
return(null);
}
viewPosition = firstChild + 1;
return(layoutManager.FindViewByPosition(firstChild + 1));
}
