/// <summary>
/// Update ScrollView scroll start position based on other scrollview scrolling
/// </summary>
public static void UpdateScrollViewStart(HeaderLayout headerLayout, ContentPage contentPage, NavigationPage navigationPage, ScrollView scrollView, double scrollY)
{
bool isNavigationBarFloating = false;
NavigationBarVisibility navBarVisibility = NavigationBarVisibility.Hidden;
double navigationBarHeight = 0;
if (contentPage != null)
{
isNavigationBarFloating = NavigationBar.GetIsFloating(contentPage);
navBarVisibility = NavigationBar.GetVisibility(contentPage);
}
if (navigationPage != null)
{
bool isNavigationBarScrollable = navBarVisibility == NavigationBarVisibility.Scroll || navBarVisibility == NavigationBarVisibility.SmoothScroll;
if (navigationPage != null && (isNavigationBarFloating || isNavigationBarScrollable))
{
navigationBarHeight = navigationPage.GetNavigationBarHeight();
}
}
if (headerLayout != null)
{
// If scrolled header hidden
if (scrollY >= headerLayout.HeaderHeight + navigationBarHeight)
{
// If scrollview is scrolled less than header height
if (scrollView.ScrollY < headerLayout.HeaderHeight + navigationBarHeight)
{
if (Device.RuntimePlatform == Device.UWP)
{
ScrollEffect effect = scrollView.Effects.FirstOrDefault(c => c is ScrollEffect) as ScrollEffect;
effect.ScrollTo(0, headerLayout.HeaderHeight + navigationBarHeight);
}
else
{
scrollView.ScrollToAsync(0, headerLayout.HeaderHeight + navigationBarHeight, false);
}
}
}
// If scrolled less than header height
else if (scrollView.ScrollY.Equals(scrollY) == false)
{
if (Device.RuntimePlatform == Device.UWP)
{
ScrollEffect effect = scrollView.Effects.FirstOrDefault(c => c is ScrollEffect) as ScrollEffect;
effect.ScrollTo(0, scrollY);
}
else
{
scrollView.ScrollToAsync(0, scrollY, false);
}
}
}
}
/// <summary>
/// Update ScrollView / CollectionView padding which are header layout content
/// </summary>
public static void UpdateScrollSourcePadding(HeaderLayout headerLayout, ContentPage contentPage, NavigationPage navigationPage, View scrollSource)
{
bool isHeaderLayoutInScrollViewer = headerLayout != null?VisualTreeHelper.GetParent <ScrollView>(headerLayout) != null : false;
// Get navigation page navigation bar height
double topPadding = 0;
if (contentPage != null && NavigationBar.GetIsFloating(contentPage) == false &&
isHeaderLayoutInScrollViewer == false &&
(NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.Scroll ||
NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.SmoothScroll))
{
topPadding += navigationPage.GetNavigationBarHeight();
}
if (headerLayout != null && isHeaderLayoutInScrollViewer == false)
{
topPadding += headerLayout.HeaderHeight;
topPadding += headerLayout.StickyHeaderHeight;
}
if (scrollSource is ScrollView scrollView)
{
if (topPadding.Equals(scrollView.Padding.Top) == false)
{
scrollView.Padding = new Thickness(scrollView.Padding.Left, topPadding, scrollView.Padding.Right, scrollView.Padding.Bottom);
}
}
else if (scrollSource is CollectionView collectionView)
{
if (collectionView.Header == null)
{
BoxView b = new BoxView();
b.HeightRequest = 0;
collectionView.Header = b;
}
if (collectionView.Header is View headerView)
{
headerView.Margin = new Thickness(headerView.Margin.Left, topPadding, headerView.Margin.Right, headerView.Margin.Bottom);
}
}
}
/// <summary>
/// Helper to get navigation bar properties
/// </summary>
public static void TryGetNavigationBarProperties(ContentPage contentPage, NavigationPage navigationPage, out double navigationBarHeight, out double navigationBarY, out bool isNavigationBarFloating, out bool isNavigationBarScrollable)
{
if (contentPage != null && navigationPage != null)
{
navigationBarHeight = NavigationBar.GetVisibility(contentPage) != NavigationBarVisibility.Hidden ? navigationPage.GetNavigationBarHeight() : 0;
isNavigationBarFloating = NavigationBar.GetIsFloating(contentPage);
isNavigationBarScrollable = NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.Scroll || NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.SmoothScroll;
if (navigationPage.GetNavigationBar() is NavigationBar navigationBar)
{
navigationBarY = navigationBar.TranslationY;
}
else
{
navigationBarY = 0;
}
}
else
{
navigationBarHeight = 0;
navigationBarY = 0;
isNavigationBarFloating = false;
isNavigationBarScrollable = false;
}
}
