void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
{
if (!_isAttached)
{
_pendingScrollTo = e;
return;
}
Cell cell;
int position;
var scrollArgs = (ITemplatedItemsListScrollToRequestedEventArgs)e;
var templatedItems = TemplatedItemsView.TemplatedItems;
if (Element.IsGroupingEnabled)
{
var results = templatedItems.GetGroupAndIndexOfItem(scrollArgs.Group, scrollArgs.Item);
if (results.Item1 == -1 || results.Item2 == -1)
{
return;
}
var group = templatedItems.GetGroup(results.Item1);
cell = group[results.Item2];
position = templatedItems.GetGlobalIndexForGroup(group) + results.Item2 + 1;
}
else
{
position = templatedItems.GetGlobalIndexOfItem(scrollArgs.Item);
if (position == -1)
{
return;
}
cell = templatedItems[position];
}
//Android offsets position of cells when using header
int realPositionWithHeader = position + 1;
if (e.Position == ScrollToPosition.MakeVisible)
{
if (e.ShouldAnimate)
{
Control.SmoothScrollToPosition(realPositionWithHeader);
}
else
{
Control.SetSelection(realPositionWithHeader);
}
return;
}
int height = Control.Height;
var cellHeight = (int)cell.RenderHeight;
if (cellHeight == -1)
{
int first = Control.FirstVisiblePosition;
if (first <= position && position <= Control.LastVisiblePosition)
{
cellHeight = Control.GetChildAt(position - first).Height;
}
else
{
AView view = _adapter.GetView(position, null, null);
view.Measure(MeasureSpecFactory.MakeMeasureSpec(Control.Width, MeasureSpecMode.AtMost), MeasureSpecFactory.MakeMeasureSpec(0, MeasureSpecMode.Unspecified));
cellHeight = view.MeasuredHeight;
}
}
var y = 0;
if (e.Position == ScrollToPosition.Center)
{
y = height / 2 - cellHeight / 2;
}
else if (e.Position == ScrollToPosition.End)
{
y = height - cellHeight;
}
if (e.ShouldAnimate)
{
Control.SmoothScrollToPositionFromTop(realPositionWithHeader, y);
}
else
{
Control.SetSelectionFromTop(realPositionWithHeader, y);
}
}
public void UpdateLayout()
{
Performance.Start(out string reference);
VisualElement view = _renderer.Element;
AView aview = _renderer.View;
var headlessOffset = CompressedLayout.GetHeadlessOffset(view);
var x = (int)_context.ToPixels(view.X + headlessOffset.X);
var y = (int)_context.ToPixels(view.Y + headlessOffset.Y);
var width = Math.Max(0, (int)_context.ToPixels(view.Width));
var height = Math.Max(0, (int)_context.ToPixels(view.Height));
var formsViewGroup = aview as FormsViewGroup;
if (formsViewGroup == null)
{
Performance.Start(reference, "Measure");
aview.Measure(MeasureSpecFactory.MakeMeasureSpec(width, MeasureSpecMode.Exactly), MeasureSpecFactory.MakeMeasureSpec(height, MeasureSpecMode.Exactly));
Performance.Stop(reference, "Measure");
Performance.Start(reference, "Layout");
aview.Layout(x, y, x + width, y + height);
Performance.Stop(reference, "Layout");
}
else
{
Performance.Start(reference, "MeasureAndLayout");
formsViewGroup.MeasureAndLayout(MeasureSpecFactory.MakeMeasureSpec(width, MeasureSpecMode.Exactly), MeasureSpecFactory.MakeMeasureSpec(height, MeasureSpecMode.Exactly), x, y, x + width, y + height);
Performance.Stop(reference, "MeasureAndLayout");
}
// If we're running sufficiently new Android, we have to make sure to update the ClipBounds to
// match the new size of the ViewGroup
if ((int)System.Maui.Maui.SdkInt >= 18)
{
UpdateClipToBounds();
}
Performance.Stop(reference);
//On Width or Height changes, the anchors needs to be updated
UpdateAnchorX();
UpdateAnchorY();
}
protected override void OnLayout(bool changed, int l, int t, int r, int b)
{
base.OnLayout(changed, l, t, r, b);
if (_viewPager != null)
{
_viewPager.Measure(MeasureSpecFactory.MakeMeasureSpec(r - l, MeasureSpecMode.Exactly), MeasureSpecFactory.MakeMeasureSpec(b - t, MeasureSpecMode.Exactly));
_viewPager.Layout(0, 0, r - l, b - t);
}
}
