Fix for ListView BindingContext for Header/Footer (#312)

* ListView - unit test showing BindingContext issue

Apparently the BC doesn't pass to Header and Footer

* ListView - support for passing BC to header and footer

* ListView - test checking BindingContext is set

Checking that it works to set the BindingContext first and the
Header/Footer after

2 files changed, 56 insertions, 0 deletions

diff --git a/Xamarin.Forms.Core.UnitTests/ListViewTests.cs b/Xamarin.Forms.Core.UnitTests/ListViewTests.cs
index d5672f77..b373696a 100644
--- a/Xamarin.Forms.Core.UnitTests/ListViewTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/ListViewTests.cs
@@ -87,6 +87,43 @@ namespace Xamarin.Forms.Core.UnitTests
 		}
 
 		[Test]
+		[Description("Setting BindingContext should trickle down to Header and Footer.")]
+		public void SettingBindingContextPassesToHeaderAndFooter()
+		{
+			var bc = new object();
+			var header = new BoxView();
+			var footer = new BoxView();
+			var listView = new ListView
+			{
+				Header = header,
+				Footer = footer,
+				BindingContext = bc,
+			};
+
+			Assert.That(header.BindingContext, Is.SameAs(bc));
+			Assert.That(footer.BindingContext, Is.SameAs(bc));
+		}
+
+		[Test]
+		[Description("Setting Header and Footer should pass BindingContext.")]
+		public void SettingHeaderFooterPassesBindingContext()
+		{
+			var bc = new object();
+			var listView = new ListView
+			{
+				BindingContext = bc,
+			};
+
+			var header = new BoxView();
+			var footer = new BoxView();
+			listView.Footer = footer;
+			listView.Header = header;
+
+			Assert.That(header.BindingContext, Is.SameAs(bc));
+			Assert.That(footer.BindingContext, Is.SameAs(bc));
+		}
+
+		[Test]
 		[Description ("Setting GroupDisplayBinding or GroupHeaderTemplate when the other is set should set the other one to null.")]
 		public void SettingGroupHeaderTemplateSetsDisplayBindingToNull()
 		{
diff --git a/Xamarin.Forms.Core/ListView.cs b/Xamarin.Forms.Core/ListView.cs
index fa9f738e..dcc13e69 100644
--- a/Xamarin.Forms.Core/ListView.cs
+++ b/Xamarin.Forms.Core/ListView.cs
@@ -87,6 +87,25 @@ namespace Xamarin.Forms
 			set { SetValue(FooterTemplateProperty, value); }
 		}
 
+		protected override void OnBindingContextChanged()
+		{
+			base.OnBindingContextChanged();
+
+			object bc = BindingContext;
+
+			var header = Header as Element;
+			if (header != null)
+			{
+				SetChildInheritedBindingContext(header, bc);
+			}
+
+			var footer = Footer as Element;
+			if (footer != null)
+			{
+				SetChildInheritedBindingContext(footer, bc);
+			}
+		}
+
 		public BindingBase GroupDisplayBinding
 		{
 			get { return _groupDisplayBinding; }