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Improved pinch zoom for ScaleAspectFit images
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| // This code is a Xamarin adaptation of https://letcreateanapp.com/2021/05/20/pinch-to-zoom-image-in-out-programmatically/ | |
| public ImageViewer() | |
| { | |
| scrollView = new UIScrollView | |
| { | |
| ShowsHorizontalScrollIndicator = false, | |
| ShowsVerticalScrollIndicator = false, | |
| BouncesZoom = false, | |
| MinimumZoomScale = 1, | |
| MaximumZoomScale = 4, | |
| }; | |
| scrollView.ViewForZoomingInScrollView = _ => imageView; | |
| scrollView.AddGestureRecognizer(new UITapGestureRecognizer(() => | |
| { | |
| scrollView.SetZoomScale( | |
| scrollView.ZoomScale > scrollView.MinimumZoomScale | |
| ? scrollView.MinimumZoomScale | |
| : scrollView.MaximumZoomScale, | |
| true); | |
| }) | |
| { | |
| NumberOfTapsRequired = 2, | |
| }); | |
| scrollView.DidZoom += ScrollViewDidZoom; | |
| } | |
| public void ScrollViewDidZoom(object s, EventArgs e) | |
| { | |
| if (scrollView.ZoomScale > 1) | |
| { | |
| if (imageView.Image != null) | |
| { | |
| var ratioW = imageView.Frame.Width / imageView.Image.Size.Width; | |
| var ratioH = imageView.Frame.Height / imageView.Image.Size.Height; | |
| var ratio = ratioW < ratioH ? ratioW : ratioH; | |
| var newWidth = imageView.Image.Size.Width * ratio; | |
| var newHeight = imageView.Image.Size.Height * ratio; | |
| var conditionLeft = newWidth * scrollView.ZoomScale > imageView.Frame.Width; | |
| var left = 0.5 * (conditionLeft ? newWidth - imageView.Frame.Width : (scrollView.Frame.Width - scrollView.ContentSize.Width)); | |
| var conditionTop = newHeight * scrollView.ZoomScale > imageView.Frame.Height; | |
| var top = 0.5 * (conditionTop ? newHeight - imageView.Frame.Height : (scrollView.Frame.Height - scrollView.ContentSize.Height)); | |
| scrollView.ContentInset = new UIEdgeInsets((nfloat)top, (nfloat)left, (nfloat)top, (nfloat)left); | |
| } | |
| } | |
| else | |
| { | |
| scrollView.ContentInset = UIEdgeInsets.Zero; | |
| } | |
| } |
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