public static void ScrollToElement(this ScrollViewer scrollViewer, UIElement element,
bool isVerticalScrolling = true, bool smoothScrolling = true, float? zoomFactor = null)
{
var transform = element.TransformToVisual((UIElement)scrollViewer.Content);
var position = transform.TransformPoint(new Point(0, 0));
if (isVerticalScrolling)
{
scrollViewer.ChangeView(null, position.Y, zoomFactor, !smoothScrolling);
}
else
{
scrollViewer.ChangeView(position.X, null, zoomFactor, !smoothScrolling);
}
}
/// <summary>
/// Scrolls to horizontal offset asynchronously.
/// </summary>
/// <param name="scrollViewer">The scroll viewer.</param>
/// <param name="offset">The offset.</param>
/// <returns>The task that completes when scrolling is complete.</returns>
public static async Task ScrollToHorizontalOffsetAsync(this ScrollViewer scrollViewer, double offset)
{
if (offset < 0)
offset = 0;
if (offset > scrollViewer.ScrollableWidth)
offset = scrollViewer.ScrollableWidth;
var currentOffset = scrollViewer.HorizontalOffset;
// ReSharper disable CompareOfFloatsByEqualityOperator
if (offset == currentOffset)
return;
#if WIN81
if (!scrollViewer.ChangeView(offset, null, null, true))
{
return;
}
#else
scrollViewer.ScrollToHorizontalOffset(offset);
#endif
if (scrollViewer.HorizontalOffset == offset)
return;
if (scrollViewer.HorizontalOffset != currentOffset)
return;
// ReSharper restore CompareOfFloatsByEqualityOperator
await EventAsync.FromEvent<ScrollViewerViewChangedEventArgs>(
eh => scrollViewer.ViewChanged += eh,
eh => scrollViewer.ViewChanged -= eh);
}
/// <summary>
/// Scrolls to vertical offset asynchronously.
/// </summary>
/// <param name="scrollViewer">The scroll viewer.</param>
/// <param name="offset">The offset.</param>
/// <returns>The task that completes when scrolling is complete.</returns>
public static async Task ScrollToVerticalOffsetAsync(this ScrollViewer scrollViewer, double offset)
{
if (offset < 0)
offset = 0;
if (offset > scrollViewer.ScrollableHeight)
offset = scrollViewer.ScrollableHeight;
var currentOffset = scrollViewer.VerticalOffset;
// ReSharper disable CompareOfFloatsByEqualityOperator
if (offset == currentOffset)
return;
if (!scrollViewer.ChangeView(null, offset, null))
{
return;
}
if (scrollViewer.VerticalOffset == offset)
return;
if (scrollViewer.VerticalOffset != currentOffset)
return;
// ReSharper restore CompareOfFloatsByEqualityOperator
await EventAsync.FromEventAsync<ScrollViewerViewChangedEventArgs>(
eh => scrollViewer.ViewChanged += eh,
eh => scrollViewer.ViewChanged -= eh);
}
/// <summary>
/// Scroll the ScrollViewer to the bottom.
/// </summary>
/// <param name="viewer">The ScrollViewer.</param>
public static void ScrollToBottom(this ScrollViewer viewer)
{
Debug.Assert(viewer != null, "viewer should not be null!");
#if WIN81
viewer.ChangeView(null, viewer.ExtentHeight, null);
#else
viewer.ScrollToVerticalOffset(viewer.ExtentHeight);
#endif
}
/// <summary>
/// Scroll the ScrollViewer to the top.
/// </summary>
/// <param name="viewer">The ScrollViewer.</param>
public static void ScrollToTop(this ScrollViewer viewer)
{
Debug.Assert(viewer != null, "viewer should not be null!");
#if WIN81
viewer.ChangeView(null, 0, null);
#else
viewer.ScrollToVerticalOffset(0);
#endif
}
/// <summary>
/// Scroll the ScrollViewer to the bottom.
/// </summary>
/// <param name="viewer">The ScrollViewer.</param>
public static void ScrollToBottom(this ScrollViewer viewer)
{
Debug.Assert(viewer != null, "viewer should not be null!");
viewer.ChangeView(null, viewer.ExtentHeight, null);
}
/// <summary>
/// Scroll the ScrollViewer to the top.
/// </summary>
/// <param name="viewer">The ScrollViewer.</param>
public static void ScrollToTop(this ScrollViewer viewer)
{
Debug.Assert(viewer != null, "viewer should not be null!");
viewer.ChangeView(null, 0, null);
}
public static async Task ChangeViewAsync(this ScrollViewer scrollViewer, double? horizontalOffset, double? verticalOffset, bool disableAnimation)
{
var tcs = new TaskCompletionSource<object>();
EventHandler<ScrollViewerViewChangedEventArgs> viewChanged = (s, e) => tcs.TrySetResult(null);
try
{
scrollViewer.ViewChanged += viewChanged;
scrollViewer.ChangeView(horizontalOffset, verticalOffset, null, disableAnimation);
await tcs.Task;
}
finally
{
scrollViewer.ViewChanged -= viewChanged;
}
}
