/// <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>
/// Update headers and navigation bar translation Y by scroll
/// </summary>
private static void HandleScrolling(HeaderLayout headerLayout, ContentPage contentPage, NavigationPage navigationPage, double oldScrollY, double newScrollY)
{
// Save previous scroll Y
if (headerLayout != null)
{
headerLayout.ScrollY = newScrollY;
}
TryGetNavigationBarProperties(contentPage, navigationPage, out double navigationBarHeight, out double navigationBarY, out bool isNavigationBarFloating, out bool isNavigationBarScrollable);
// Scroll delta
double delta = Math.Max(0, newScrollY) - Math.Max(0, oldScrollY);
// Update navigation bar translation when it should scroll out smoothly or not
if (navigationPage != null && contentPage != null &&
(NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.Scroll ||
NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.SmoothScroll))
{
View navigationBar = navigationPage.GetNavigationBar();
// Hide navigation bar smoothly
if (NavigationBar.GetVisibility(contentPage) == NavigationBarVisibility.SmoothScroll && navigationBar != null)
{
// If scrolled enought speed do smooth navigation bar hiding with animation
if (Math.Abs(delta) > 5)
{
string showScrollBarAnimationName = "showScrollBarAnimation";
string hideScrollBarAnimationName = "hideScrollBarAnimation";
double start = navigationBar.TranslationY;
double target = 0;
string actualAnimationName;
if (delta < 0)
{
target = 0;
actualAnimationName = showScrollBarAnimationName;
}
else
{
target = -navigationBarHeight + RootPage.Instance.SafeAreaInsest.Top;
actualAnimationName = hideScrollBarAnimationName;
}
if (target != navigationBar.TranslationY && AnimationExtensions.AnimationIsRunning(navigationBar, actualAnimationName) == false)
{
AnimationExtensions.AbortAnimation(navigationBar, showScrollBarAnimationName);
AnimationExtensions.AbortAnimation(navigationBar, hideScrollBarAnimationName);
new Animation(d =>
{
// Animate NavigastionBar TranslationY
navigationBar.TranslationY = start + (target - start) * d;
// Get NavigationBar properties during animation because they can change
TryGetNavigationBarProperties(contentPage, navigationPage, out navigationBarHeight, out navigationBarY, out isNavigationBarFloating, out isNavigationBarScrollable);
// Update headers transaltion because navigation bar translation is animated
headerLayout?.UpdateHeadersTranslationY(headerLayout.ScrollY, navigationBarHeight, navigationBarY, isNavigationBarFloating, isNavigationBarScrollable);
}, 0, 1).Commit(navigationBar, actualAnimationName, 64, 250);
}
else
{
headerLayout?.UpdateHeadersTranslationY(newScrollY, navigationBarHeight, navigationBar.TranslationY, isNavigationBarFloating, isNavigationBarScrollable);
}
}
// If not scrolled enought speed, then hide other headers normally
else
{
headerLayout?.UpdateHeadersTranslationY(newScrollY, navigationBarHeight, navigationBar.TranslationY, isNavigationBarFloating, isNavigationBarScrollable);
}
}
// Hide navigation bar based on scroll only
else
{
navigationBar.TranslationY = Math.Min(0, Math.Max(-navigationBarHeight + RootPage.Instance.SafeAreaInsest.Top, navigationBar.TranslationY - delta));
navigationBarY = navigationBar.TranslationY;
headerLayout?.UpdateHeadersTranslationY(newScrollY, navigationBarHeight, navigationBarY, isNavigationBarFloating, isNavigationBarScrollable);
}
}
// If navigation bar is visible or hidden
else
{
headerLayout?.UpdateHeadersTranslationY(newScrollY, navigationBarHeight, navigationBarY, isNavigationBarFloating, isNavigationBarScrollable);
}
}
