public static void ScrollVerticallyTo(ScrollRect parentScrollRect, UiEventNavigation childControl, Dictionary <UiEventNavigation, SingleAxisBounds> cacheDict = null, bool centerTo = false)
{
if ((parentScrollRect != null) && (childControl != null) && (childControl.Selectable != null))
{
// Check the cache, and see if the bounds for this child control already exists
SingleAxisBounds childBounds;
if ((cacheDict == null) || (cacheDict.TryGetValue(childControl, out childBounds) == false))
{
// Calculate the top and bottom position of the the control
float topPos, centerPos, bottomPos;
centerPos = GetVerticalAnchoredPositionInContent(parentScrollRect.content, childControl, out topPos, out bottomPos);
childBounds = new SingleAxisBounds(topPos, centerPos, bottomPos);
// Cache these values
if (cacheDict != null)
{
cacheDict.Add(childControl, childBounds);
}
}
// Check whether we need to scroll or not, and if so, in which snapping direction
ScrollVerticalSnap snapTo = ScrollVerticalSnap.CenterToChild;
if (centerTo == false)
{
snapTo = GetVerticalSnapping(parentScrollRect.content, parentScrollRect.viewport, ref childBounds);
}
// Check whether we want to scroll or not
if (snapTo != ScrollVerticalSnap.None)
{
// Grab the position to scroll to
float selectionPosition = GetScrollToPosition(parentScrollRect.viewport, snapTo, ref childBounds);
// Clamp the selection position value
float maxPosition = (parentScrollRect.content.rect.height - parentScrollRect.viewport.rect.height);
selectionPosition = Mathf.Clamp(selectionPosition, 0, maxPosition);
// Directly set the position of the ScrollRect's content
Vector3 scrollPosition = parentScrollRect.content.anchoredPosition;
scrollPosition.y = selectionPosition;
parentScrollRect.content.anchoredPosition = scrollPosition;
}
}
}
private static float GetScrollToPosition(RectTransform viewportTransform, ScrollVerticalSnap snapTo, ref SingleAxisBounds childBounds)
{
// By default, snap to the top of the child control
float childControlPosition = childBounds.max;
// Check the snap-to algorithm
if (snapTo == ScrollVerticalSnap.BottomOfChild)
{
// Shift the scroll position to the bottom of the scrollrect
childControlPosition = childBounds.min;
childControlPosition += viewportTransform.rect.height;
}
else if (snapTo == ScrollVerticalSnap.CenterToChild)
{
// Shift the scroll position to the center of the scrollrect
childControlPosition = childBounds.middle;
childControlPosition += (viewportTransform.rect.height / 2f);
}
childControlPosition *= -1f;
return(childControlPosition);
}
private static ScrollVerticalSnap GetVerticalSnapping(RectTransform contentTransform, RectTransform viewportTransform, ref SingleAxisBounds childBounds)
{
ScrollVerticalSnap returnOffset = ScrollVerticalSnap.None;
float topOfChildControl = childBounds.max;
float bottomOfChildControl = childBounds.min;
// Check if viewport is smaller than content
float viewportHeight = viewportTransform.rect.height;
if (contentTransform.rect.height > viewportHeight)
{
// Based on these values, determine whether to snap to the top or bottom of out-of-view child control
if (Mathf.Abs(topOfChildControl) < contentTransform.anchoredPosition.y)
{
returnOffset = ScrollVerticalSnap.TopOfChild;
}
else if (Mathf.Abs(bottomOfChildControl) > (contentTransform.anchoredPosition.y + viewportHeight))
{
returnOffset = ScrollVerticalSnap.BottomOfChild;
}
}
return(returnOffset);
}
