Resolved null ref when changing control height within a FlexLayout. A…

…lso simplified the code slightly.
Liam2349 · Jan 17, 2019 · 50701ae · 50701ae
1 parent 4fe7f92
commit 50701ae
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Showing 2 changed files with 15 additions and 14 deletions.
diff --git a/Xamarin.Forms.Core/FlexLayout.cs b/Xamarin.Forms.Core/FlexLayout.cs
@@ -341,19 +341,18 @@ void RemoveChild(View view)
 
 		void OnChildPropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
-			if (   e.PropertyName == WidthRequestProperty.PropertyName
-				|| e.PropertyName == HeightRequestProperty.PropertyName) {
-				var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
+			var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
+			if (item == null)
+				return;
+
+			if (e.PropertyName == WidthRequestProperty.PropertyName || e.PropertyName == HeightRequestProperty.PropertyName) {
 				item.Width = ((View)sender).WidthRequest < 0 ? float.NaN : (float)((View)sender).WidthRequest;
 				item.Height = ((View)sender).HeightRequest < 0 ? float.NaN : (float)((View)sender).HeightRequest;
 				InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
 				return;
 			}
 
 			if (e.PropertyName == MarginProperty.PropertyName) {
-				var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
-				if (item == null)
-					return;
 				var margin = (Thickness)((View)sender).GetValue(MarginProperty);
 				item.MarginLeft = (float)margin.Left;
 				item.MarginTop = (float)margin.Top;
@@ -364,9 +363,6 @@ void OnChildPropertyChanged(object sender, PropertyChangedEventArgs e)
 			}
 
 			if (e.PropertyName == PaddingProperty.PropertyName) {
-				var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
-				if (item == null)
-					return;
 				var padding = (Thickness)((View)sender).GetValue(PaddingProperty);
 				item.PaddingLeft = (float)padding.Left;
 				item.PaddingTop = (float)padding.Top;
@@ -377,9 +373,6 @@ void OnChildPropertyChanged(object sender, PropertyChangedEventArgs e)
 			}
 
 			if (e.PropertyName == IsVisibleProperty.PropertyName) {
-				var item = (sender as FlexLayout)?._root ?? GetFlexItem((BindableObject)sender);
-				if (item == null)
-					return;
 				item.IsVisible = (bool)((View)sender).GetValue(IsVisibleProperty);
 				InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
 				return;

diff --git a/Xamarin.Forms.Core/StackLayout.cs b/Xamarin.Forms.Core/StackLayout.cs
@@ -60,8 +60,16 @@ protected override void LayoutChildren(double x, double y, double width, double
 			for (var i = 0; i < LogicalChildrenInternal.Count; i++)
 			{
 				var child = (View)LogicalChildrenInternal[i];
-                try { if (child.IsVisible) LayoutChildIntoBoundingRegion(child, _layoutInformation.Plots[i], _layoutInformation.Requests[i]); }
-                catch (NullReferenceException) { return; }
+                try
+				{
+					if (child.IsVisible)
+						LayoutChildIntoBoundingRegion(child, _layoutInformation.Plots[i], _layoutInformation.Requests[i]);
+				}
+                catch (NullReferenceException)
+				{
+					if (_layoutInformation.Plots != null || _layoutInformation.Requests != null) throw;
+					return;
+				}
 			}
 		}