Xamarin.Forms.Platform.iOS/NativeViewWrapperRenderer.cs


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67

using CoreGraphics;
using UIKit;
using Xamarin.Forms.Internals;

namespace Xamarin.Forms.Platform.iOS
{
	public class NativeViewWrapperRenderer : ViewRenderer<NativeViewWrapper, UIView>
	{
		public override SizeRequest GetDesiredSize(double widthConstraint, double heightConstraint)
		{
			if (Element?.GetDesiredSizeDelegate == null)
				return base.GetDesiredSize(widthConstraint, heightConstraint);

			// The user has specified a different implementation of GetDesiredSize
			var result = Element.GetDesiredSizeDelegate(this, widthConstraint, heightConstraint);

			// If the GetDesiredSize delegate returns a SizeRequest, we use it; if it returns null,
			// fall back to the default implementation
			return result ?? base.GetDesiredSize(widthConstraint, heightConstraint);
		}

		public override void LayoutSubviews()
		{
			if (Element?.LayoutSubViews == null)
			{
				((IVisualElementController)Element)?.InvalidateMeasure(InvalidationTrigger.MeasureChanged);
				base.LayoutSubviews();
				return;
			}

			// The user has specified a different implementation of LayoutSubviews
			var handled = Element.LayoutSubViews();

			if (!handled)
			{
				// If the delegate wasn't able to handle the request, fall back to the default implementation
				base.LayoutSubviews();
			}
		}

		public override CGSize SizeThatFits(CGSize size)
		{
			if (Element?.SizeThatFitsDelegate == null)
				return base.SizeThatFits(size);

			// The user has specified a different implementation of SizeThatFits
			var result = Element.SizeThatFitsDelegate(size);

			// If the delegate returns a value, we use it; 
			// if it returns null, fall back to the default implementation
			return result ?? base.SizeThatFits(size);
		}

		protected override void OnElementChanged(ElementChangedEventArgs<NativeViewWrapper> e)
		{
			base.OnElementChanged(e);

			if (e.OldElement == null)
				SetNativeControl(Element.NativeView);
		}

		/// <summary>
		/// The native control we're wrapping isn't ours to dispose of
		/// </summary>
		protected override bool ManageNativeControlLifetime => false;
	}
}