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An enhanced version of Android's ViewPager.PageScrolled event using Reactive Extensions.
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Observable.FromEventPattern<ViewPager.PageScrolledEventArgs> ( | |
x => _viewPager.PageScrolled += x, | |
x => _viewPager.PageScrolled -= x) | |
.Select (args => args.EventArgs) | |
.StartWith(new ViewPager.PageScrolledEventArgs(0, 0, 0)) | |
.PairWithPrevious() | |
.Skip(1) | |
.Select(args => { | |
var scrollDirection = | |
args.Item1.Position != args.Item2.Position | |
? ScrollDirection.Center | |
: args.Item1.PositionOffset > args.Item2.PositionOffset | |
? ScrollDirection.Left | |
: ScrollDirection.Right; | |
return new { | |
Current = _pagerAdapter.GetItem(args.Item2.Position) as Walkthrough, | |
Next = _pagerAdapter.GetItem(args.Item2.Position+1) as Walkthrough, | |
ScrollDirection = scrollDirection, | |
args.Item2.PositionOffset, | |
}; | |
}) | |
.Where(args => args.ScrollDirection == ScrollDirection.Center || args.Current != null && args.Next != null) | |
.Subscribe (args => { | |
if (args.ScrollDirection == ScrollDirection.Center) { | |
args.Current.View?.SetBackgroundColor (args.Current.ViewModel.BackgroundColor.ToNative()); | |
} else if (args.ScrollDirection == ScrollDirection.Left || args.ScrollDirection == ScrollDirection.Right) { | |
var color = args.Current.ViewModel.BackgroundColor.Lerp (args.Next.ViewModel.BackgroundColor, args.PositionOffset).ToNative (); | |
args.Current.View?.SetBackgroundColor (color); | |
args.Next.View?.SetBackgroundColor (color); | |
} | |
}).DisposeWith(ControlBindings); |
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