/// <summary>
/// Initializes a new instance of the <see cref="ExtendedScrollViewPage"/> class.
/// </summary>
public ExtendedScrollViewPage()
{
InitializeComponent();
var container = new StackLayout()
{
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand
};
var buttonToScroll = new Button() { Text = "Scroll to end" };
container.Children.Add(buttonToScroll);
for (var i = 0; i < 10; i++)
{
container.Children.Add(new Image
{
Aspect = Aspect.AspectFill,
Source = ImageSource.FromUri(new Uri("http://www.stockvault.net/data/2011/05/31/124348/small.jpg")),
HeightRequest = IMAGE_HEIGHT
});
}
var sv = new ExtendedScrollView
{
Content = container,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand
};
sv.Scrolled += async (arg1, arg2) =>
{
if (!(arg2.Y > sv.Bounds.Height) || _displayAlert)
{
return;
}
_displayAlert = true;
await DisplayAlert("Scroll event", "User scrolled pass bounds", "Ok", "cancel");
};
buttonToScroll.Clicked += (sender, e) =>
{
sv.Position = new Point(sv.Position.X, sv.ContentSize.Height - IMAGE_HEIGHT);
};
Content = sv;
}
/// <summary>
/// Handles the <see cref="E:ElementChanged" /> event.
/// </summary>
/// <param name="e">The <see cref="VisualElementChangedEventArgs"/> instance containing the event data.</param>
protected override void OnElementChanged(VisualElementChangedEventArgs e)
{
base.OnElementChanged(e);
Scrolled += (sender, ev) => {
ExtendedScrollView sv = (ExtendedScrollView)Element;
sv.UpdateBounds(Bounds.ToRectangle());
};
if (e.OldElement != null)
{
e.OldElement.PropertyChanged -= OnElementPropertyChanged;
}
e.NewElement.PropertyChanged += OnElementPropertyChanged;
}
/// <summary>
/// Handles the <see cref="E:ElementPropertyChanged" /> event.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="e">The <see cref="PropertyChangedEventArgs"/> instance containing the event data.</param>
protected void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == ExtendedScrollView.PositionProperty.PropertyName)
{
ExtendedScrollView sv = (ExtendedScrollView)Element;
Point pt = sv.Position;
if (System.Math.Abs(Bounds.Location.Y - pt.Y) < _epsilon &&
System.Math.Abs(Bounds.Location.X - pt.X) < _epsilon)
{
return;
}
ScrollRectToVisible(
new CGRect((float)pt.X, (float)pt.Y, Bounds.Width, Bounds.Height), sv.AnimateScroll);
}
}
