void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
{
if (_animatable == null && e.ShouldAnimate)
{
_animatable = new Animatable();
}
ScrollToPosition position = e.Position;
double x = e.ScrollX;
double y = e.ScrollY;
if (e.Mode == ScrollToMode.Element)
{
Point itemPosition = Controller.GetScrollPositionForElement(e.Element as VisualElement, e.Position);
x = itemPosition.X;
y = itemPosition.Y;
}
if (Control.VerticalOffset == y && Control.HorizontalOffset == x)
{
return;
}
if (e.ShouldAnimate)
{
var animation = new Animation(v => { UpdateScrollOffset(GetDistance(Control.ViewportWidth, x, v), GetDistance(Control.ViewportHeight, y, v)); });
animation.Commit(_animatable, "ScrollTo", length: 500, easing: Easing.CubicInOut, finished: (v, d) =>
{
UpdateScrollOffset(x, y);
Controller.SendScrollFinished();
});
}
else
{
UpdateScrollOffset(x, y);
Controller.SendScrollFinished();
}
}
void OnScrollToRequested(object sender, ScrollToRequestedEventArgs e)
{
if (_animatable == null && e.ShouldAnimate)
{
_animatable = new Animatable();
}
if (_viewport == null)
{
// Making sure we're actually loaded
if (VisualTreeHelper.GetChildrenCount(_listBox) == 0)
{
RoutedEventHandler handler = null;
handler = (o, args) =>
{
Control.Loaded -= handler;
OnScrollToRequested(sender, e);
};
Control.Loaded += handler;
return;
}
_viewport = (ViewportControl)VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(_listBox, 0), 0), 0);
if (_viewport.Viewport.Bottom == 0)
{
EventHandler <ViewportChangedEventArgs> viewportChanged = null;
viewportChanged = (o, args) =>
{
if (_viewport.Viewport.Bottom == 0)
{
return;
}
_viewport.ViewportChanged -= viewportChanged;
OnScrollToRequested(sender, e);
};
_viewport.ViewportChanged += viewportChanged;
return;
}
}
double y = 0;
double targetHeight = 0;
double targetHeaderHeight = 0;
var templateReusables = new Dictionary <System.Windows.DataTemplate, FrameworkElement>();
var found = false;
if (Element.IsGroupingEnabled)
{
for (var g = 0; g < Element.TemplatedItems.Count; g++)
{
if (found)
{
break;
}
TemplatedItemsList <ItemsView <Cell>, Cell> til = Element.TemplatedItems.GetGroup(g);
double headerHeight = GetHeight(templateReusables, Control.GroupHeaderTemplate, til);
y += headerHeight;
for (var i = 0; i < til.Count; i++)
{
Cell cell = til[i];
double contentHeight = GetHeight(templateReusables, Control.ItemTemplate, cell);
if ((ReferenceEquals(til.BindingContext, e.Group) || e.Group == null) && ReferenceEquals(cell.BindingContext, e.Item))
{
targetHeaderHeight = headerHeight;
targetHeight = contentHeight;
found = true;
break;
}
y += contentHeight;
}
}
}
else
{
for (var i = 0; i < Element.TemplatedItems.Count; i++)
{
Cell cell = Element.TemplatedItems[i];
double height = GetHeight(templateReusables, Control.ItemTemplate, cell);
if (ReferenceEquals(cell.BindingContext, e.Item))
{
found = true;
targetHeight = height;
break;
}
y += height;
}
}
if (!found)
{
return;
}
ScrollToPosition position = e.Position;
if (position == ScrollToPosition.MakeVisible)
{
if (y >= _viewport.Viewport.Top && y <= _viewport.Viewport.Bottom)
{
return;
}
if (y > _viewport.Viewport.Bottom)
{
position = ScrollToPosition.End;
}
else
{
position = ScrollToPosition.Start;
}
}
if (position == ScrollToPosition.Start && Element.IsGroupingEnabled)
{
y = y - targetHeaderHeight;
}
else if (position == ScrollToPosition.Center)
{
y = y - (_viewport.ActualHeight / 2 + targetHeight / 2);
}
else if (position == ScrollToPosition.End)
{
y = y - _viewport.ActualHeight + targetHeight;
}
double startY = _viewport.Viewport.Y;
double distance = y - startY;
if (e.ShouldAnimate)
{
var animation = new Animation(v => { _viewport.SetViewportOrigin(new System.Windows.Point(0, startY + distance * v)); });
animation.Commit(_animatable, "ScrollTo", length: 500, easing: Easing.CubicInOut);
}
else
{
_viewport.SetViewportOrigin(new System.Windows.Point(0, y));
}
}