As @Cole commented, the flashScrollIndicators
can only show the indicator a short time.
So, you have to customize a scroll indicator.
Create a custom renderer of the ListView and add your custom scroll indicator, like this:
public class MyListViewRenderer : ListViewRenderer
{
public UIView bar;
protected override void OnElementChanged(ElementChangedEventArgs<ListView> e)
{
base.OnElementChanged(e);
//Hide the default Scroll Indicator.
Control.ShowsVerticalScrollIndicator = false;
//Set Delegate
CustomScrollDelegate customScrollDelegate = new CustomScrollDelegate();
Control.Delegate = customScrollDelegate;
//Create the background view of custom indicator.
double frameHeight = Control.Frame.Size.Height;
double frameWidth = Control.Frame.Size.Width;
double barBackgroundWidth = 6;
double statusBarHeight = 20;
UIView barBackgroundView = new UIView();
CGRect barBVRect = new CGRect(frameWidth - barBackgroundWidth, statusBarHeight, barBackgroundWidth, frameHeight);
barBackgroundView.Frame = barBVRect;
barBackgroundView.BackgroundColor = UIColor.Gray;
barBackgroundView.Layer.CornerRadius = 2;
barBackgroundView.Layer.MasksToBounds = true;
//Create the bar of the custom indicator.
bar = new UIView();
CGRect barRect = new CGRect(1, 0, 4, 0);
bar.Frame = barRect;
bar.BackgroundColor = UIColor.Black;
bar.Layer.CornerRadius = 2;
bar.Layer.MasksToBounds = true;
//Add the views to the superview of the tableview.
barBackgroundView.AddSubview(bar);
Control.Superview.AddSubview(barBackgroundView);
//Transfer the bar view to delegate.
customScrollDelegate.bar = bar;
}
public override void LayoutSubviews()
{
base.LayoutSubviews();
Console.WriteLine("End of loading!!!");
double contentHeight = Control.ContentSize.Height;
double frameHeight = Control.Frame.Size.Height;
double barHeight = frameHeight * frameHeight / contentHeight;
//Reset the bar height when the table view finishes loading.
CGRect barRect = new CGRect(bar.Frame.X, bar.Frame.Y, bar.Frame.Width, barHeight);
bar.Frame = barRect;
}
}
Implement the Scrolled
delegate which tracks the scrolling action of the scrollView. You can update the position of the indicator in the delegate.
public class CustomScrollDelegate : UIKit.UITableViewDelegate
{
public UIView bar;
double barY;
public override void Scrolled(UIScrollView scrollView)
{
double y = scrollView.ContentOffset.Y;
double contentHeight = scrollView.ContentSize.Height;
double frameHeight = scrollView.Frame.Size.Height;
double barHeight = frameHeight * frameHeight / contentHeight;
barY = y / (contentHeight - frameHeight) * (frameHeight - barHeight);
//Cut the bar Height when it over the top.
if (barY < 0)
{
barHeight = barHeight + barY;
barY = 0;
}
//Cut the bar height when it over the bottom.
if (barY > (frameHeight - barHeight))
{
barHeight = barHeight - (barY - (frameHeight - barHeight));
}
//Reset the barView rect. Let's move!!!
CGRect barRect = new CGRect(bar.Frame.X, barY, bar.Frame.Width, barHeight);
bar.Frame = barRect;
}
}
It works like this:
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…