Update RelativeLayout to make it respond to constraint changes (#425)

* Update RelativeLayout to make it respond to constraint changes Constraints of a RelativeLayout are bindable properties but the layout does not update when the constraints are updated. This change will invalidate the layout whenever XConstraint, YConstraint, WidthConstraint or HeightConstraint is changed (either in code or through a change in the bound property) * Specified changed handler as named property * Adding attached property accessors for layout properties Since the constraint attached properties can now be updated at runtime, setters are required for those properties. Also, when adding a child view at runtime using the Add() method with x/y/w/h constraints, generating the bounds constraints is deferred to the layout phase. * Unit tests for runtime constraints updates in RelativeLayout * Rename unit test method Rename LayoutChangesAtRuntim() to LayoutIsUpdatedWhenConstraintsChange() * Wrap RelativeLayout update setters in BatchBegin/Commit * Update documentation of RelativeLayout Added SetXConstraint(), SetYConstraint(), SetWidthConstraint() and SetHeightConstraint()
xamarin · Feb 2, 2017 · 01a56f9 · 01a56f9
1 parent 9a6c9a0
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Showing 3 changed files with 179 additions and 8 deletions.
diff --git a/Xamarin.Forms.Core.UnitTests/RelativeLayoutTests.cs b/Xamarin.Forms.Core.UnitTests/RelativeLayoutTests.cs
@@ -74,6 +74,47 @@ public void SimpleLayout ()
 			Assert.AreEqual (new Rectangle (30, 20, 50, 25), child.Bounds);
 		}
 
+		[Test]
+		public void LayoutIsUpdatedWhenConstraintsChange()
+		{
+			var relativeLayout = new RelativeLayout
+			{
+				Platform = new UnitPlatform(),
+				IsPlatformEnabled = true
+			};
+
+			var child = new View
+			{
+				IsPlatformEnabled = true
+			};
+
+			relativeLayout.Children.Add(child,
+								Constraint.Constant(30),
+								Constraint.Constant(20),
+								Constraint.RelativeToParent(parent => parent.Height / 2),
+								Constraint.RelativeToParent(parent => parent.Height / 4));
+
+			relativeLayout.Layout(new Rectangle(0, 0, 100, 100));
+
+			Assert.AreEqual(new Rectangle(30, 20, 50, 25), child.Bounds);
+
+			RelativeLayout.SetXConstraint(child, Constraint.Constant(40));
+
+			Assert.AreEqual(new Rectangle(40, 20, 50, 25), child.Bounds);
+
+			RelativeLayout.SetYConstraint(child, Constraint.Constant(10));
+
+			Assert.AreEqual(new Rectangle(40, 10, 50, 25), child.Bounds);
+
+			RelativeLayout.SetWidthConstraint(child, Constraint.RelativeToParent(parent => parent.Height / 4));
+
+			Assert.AreEqual(new Rectangle(40, 10, 25, 25), child.Bounds);
+
+			RelativeLayout.SetHeightConstraint(child, Constraint.RelativeToParent(parent => parent.Height / 2));
+
+			Assert.AreEqual(new Rectangle(40, 10, 25, 50), child.Bounds);
+		}
+
 		[Test]
 		public void SimpleExpressionLayout ()
 		{

diff --git a/Xamarin.Forms.Core/RelativeLayout.cs b/Xamarin.Forms.Core/RelativeLayout.cs
@@ -8,13 +8,13 @@ namespace Xamarin.Forms
 {
 	public class RelativeLayout : Layout<View>
 	{
-		public static readonly BindableProperty XConstraintProperty = BindableProperty.CreateAttached("XConstraint", typeof(Constraint), typeof(RelativeLayout), null);
+		public static readonly BindableProperty XConstraintProperty = BindableProperty.CreateAttached("XConstraint", typeof(Constraint), typeof(RelativeLayout), null, propertyChanged: ConstraintChanged);
 
-		public static readonly BindableProperty YConstraintProperty = BindableProperty.CreateAttached("YConstraint", typeof(Constraint), typeof(RelativeLayout), null);
+		public static readonly BindableProperty YConstraintProperty = BindableProperty.CreateAttached("YConstraint", typeof(Constraint), typeof(RelativeLayout), null, propertyChanged: ConstraintChanged);
 
-		public static readonly BindableProperty WidthConstraintProperty = BindableProperty.CreateAttached("WidthConstraint", typeof(Constraint), typeof(RelativeLayout), null);
+		public static readonly BindableProperty WidthConstraintProperty = BindableProperty.CreateAttached("WidthConstraint", typeof(Constraint), typeof(RelativeLayout), null, propertyChanged: ConstraintChanged);
 
-		public static readonly BindableProperty HeightConstraintProperty = BindableProperty.CreateAttached("HeightConstraint", typeof(Constraint), typeof(RelativeLayout), null);
+		public static readonly BindableProperty HeightConstraintProperty = BindableProperty.CreateAttached("HeightConstraint", typeof(Constraint), typeof(RelativeLayout), null, propertyChanged: ConstraintChanged);
 
 		public static readonly BindableProperty BoundsConstraintProperty = BindableProperty.CreateAttached("BoundsConstraint", typeof(BoundsConstraint), typeof(RelativeLayout), null);
 
@@ -72,6 +72,25 @@ IEnumerable<View> ChildrenInSolveOrder
 			}
 		}
 
+		static void ConstraintChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			View view = bindable as View;
+
+			(view?.Parent as RelativeLayout)?.UpdateBoundsConstraint(view);
+		}
+
+		void UpdateBoundsConstraint(View view)
+		{
+			if (GetBoundsConstraint(view) == null)
+				return; // Bounds constraint hasn't been calculated yet, no need to update just yet
+
+			CreateBoundsFromConstraints(view, GetXConstraint(view), GetYConstraint(view), GetWidthConstraint(view), GetHeightConstraint(view));
+
+			_childrenInSolveOrder = null; // New constraints may have impact on solve order
+
+			InvalidateLayout();
+		}
+
 		public static BoundsConstraint GetBoundsConstraint(BindableObject bindable)
 		{
 			return (BoundsConstraint)bindable.GetValue(BoundsConstraintProperty);
@@ -102,6 +121,26 @@ public static void SetBoundsConstraint(BindableObject bindable, BoundsConstraint
 			bindable.SetValue(BoundsConstraintProperty, value);
 		}
 
+		public static void SetHeightConstraint(BindableObject bindable, Constraint value)
+		{
+			bindable.SetValue(HeightConstraintProperty, value);
+		}
+
+		public static void SetWidthConstraint(BindableObject bindable, Constraint value)
+		{
+			bindable.SetValue(WidthConstraintProperty, value);
+		}
+
+		public static void SetXConstraint(BindableObject bindable, Constraint value)
+		{
+			bindable.SetValue(XConstraintProperty, value);
+		}
+
+		public static void SetYConstraint(BindableObject bindable, Constraint value)
+		{
+			bindable.SetValue(YConstraintProperty, value);
+		}
+
 		protected override void LayoutChildren(double x, double y, double width, double height)
 		{
 			foreach (View child in ChildrenInSolveOrder)
@@ -248,13 +287,13 @@ void CreateBoundsFromConstraints(View view, Constraint xConstraint, Constraint y
 		static Rectangle SolveView(View view)
 		{
 			BoundsConstraint boundsConstraint = GetBoundsConstraint(view);
-			var result = new Rectangle();
 
 			if (boundsConstraint == null)
 			{
 				throw new Exception("BoundsConstraint should not be null at this point");
 			}
-			result = boundsConstraint.Compute();
+
+			var result = boundsConstraint.Compute();
 
 			return result;
 		}
@@ -280,7 +319,7 @@ public RelativeElementCollection(ObservableCollection<Element> inner, RelativeLa
 			public void Add(View view, Expression<Func<Rectangle>> bounds)
 			{
 				if (bounds == null)
-					throw new ArgumentNullException("bounds");
+					throw new ArgumentNullException(nameof(bounds));
 				SetBoundsConstraint(view, BoundsConstraint.FromExpression(bounds));
 
 				base.Add(view);
@@ -308,7 +347,14 @@ public void Add(View view, Expression<Func<double>> x = null, Expression<Func<do
 
 			public void Add(View view, Constraint xConstraint = null, Constraint yConstraint = null, Constraint widthConstraint = null, Constraint heightConstraint = null)
 			{
-				Parent.CreateBoundsFromConstraints(view, xConstraint, yConstraint, widthConstraint, heightConstraint);
+				view.BatchBegin();
+
+				RelativeLayout.SetXConstraint(view, xConstraint);
+				RelativeLayout.SetYConstraint(view, yConstraint);
+				RelativeLayout.SetWidthConstraint(view, widthConstraint);
+				RelativeLayout.SetHeightConstraint(view, heightConstraint);
+
+				view.BatchCommit();
 
 				base.Add(view);
 			}

diff --git a/docs/Xamarin.Forms.Core/Xamarin.Forms/RelativeLayout.xml b/docs/Xamarin.Forms.Core/Xamarin.Forms/RelativeLayout.xml
@@ -446,6 +446,90 @@ public class RelativeLayoutExample : ContentPage
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
+    <Member MemberName="SetHeightConstraint">
+      <MemberSignature Language="C#" Value="public static void SetHeightConstraint (Xamarin.Forms.BindableObject bindable, Xamarin.Forms.Constraint value);" />
+      <MemberSignature Language="ILAsm" Value=".method public static hidebysig void SetHeightConstraint(class Xamarin.Forms.BindableObject bindable, class Xamarin.Forms.Constraint value) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Void</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="bindable" Type="Xamarin.Forms.BindableObject" />
+        <Parameter Name="value" Type="Xamarin.Forms.Constraint" />
+      </Parameters>
+      <Docs>
+        <param name="bindable">The <see cref="T:Xamarin.Forms.BindableObject" /> to which the constraint will be applied.</param>
+        <param name="value">The <see cref="T:Xamarin.Forms.Constraint" /> on the height of the <paramref name="bindable" />.</param>
+        <summary>Sets <paramref name="value" /> as a constraint on the height of the <paramref name="bindable" />.</summary>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
+    <Member MemberName="SetWidthConstraint">
+      <MemberSignature Language="C#" Value="public static void SetWidthConstraint (Xamarin.Forms.BindableObject bindable, Xamarin.Forms.Constraint value);" />
+      <MemberSignature Language="ILAsm" Value=".method public static hidebysig void SetWidthConstraint(class Xamarin.Forms.BindableObject bindable, class Xamarin.Forms.Constraint value) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Void</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="bindable" Type="Xamarin.Forms.BindableObject" />
+        <Parameter Name="value" Type="Xamarin.Forms.Constraint" />
+      </Parameters>
+      <Docs>
+        <param name="bindable">The <see cref="T:Xamarin.Forms.BindableObject" /> to which the constraint will be applied.</param>
+        <param name="value">The <see cref="T:Xamarin.Forms.Constraint" /> on the width of the <paramref name="bindable" />.</param>
+        <summary>Sets <paramref name="value" /> as a constraint on the width of the <paramref name="bindable" />.</summary>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
+    <Member MemberName="SetXConstraint">
+      <MemberSignature Language="C#" Value="public static void SetXConstraint (Xamarin.Forms.BindableObject bindable, Xamarin.Forms.Constraint value);" />
+      <MemberSignature Language="ILAsm" Value=".method public static hidebysig void SetXConstraint(class Xamarin.Forms.BindableObject bindable, class Xamarin.Forms.Constraint value) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Void</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="bindable" Type="Xamarin.Forms.BindableObject" />
+        <Parameter Name="value" Type="Xamarin.Forms.Constraint" />
+      </Parameters>
+      <Docs>
+        <param name="bindable">The <see cref="T:Xamarin.Forms.BindableObject" /> to which the constraint will be applied.</param>
+        <param name="value">The <see cref="T:Xamarin.Forms.Constraint" /> on the X position of the <paramref name="bindable" />.</param>
+        <summary>Sets <paramref name="value" /> as a constraint on the X position of the <paramref name="bindable" />.</summary>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
+    <Member MemberName="SetYConstraint">
+      <MemberSignature Language="C#" Value="public static void SetYConstraint (Xamarin.Forms.BindableObject bindable, Xamarin.Forms.Constraint value);" />
+      <MemberSignature Language="ILAsm" Value=".method public static hidebysig void SetYConstraint(class Xamarin.Forms.BindableObject bindable, class Xamarin.Forms.Constraint value) cil managed" />
+      <MemberType>Method</MemberType>
+      <AssemblyInfo>
+        <AssemblyVersion>2.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.Void</ReturnType>
+      </ReturnValue>
+      <Parameters>
+        <Parameter Name="bindable" Type="Xamarin.Forms.BindableObject" />
+        <Parameter Name="value" Type="Xamarin.Forms.Constraint" />
+      </Parameters>
+      <Docs>
+        <param name="bindable">The <see cref="T:Xamarin.Forms.BindableObject" /> to which the constraint will be applied.</param>
+        <param name="value">The <see cref="T:Xamarin.Forms.Constraint" /> on the Y position of the <paramref name="bindable" />.</param>
+        <summary>Sets <paramref name="value" /> as a constraint on the Y position of the <paramref name="bindable" />.</summary>
+        <remarks>To be added.</remarks>
+      </Docs>
+    </Member>
     <Member MemberName="WidthConstraintProperty">
       <MemberSignature Language="C#" Value="public static readonly Xamarin.Forms.BindableProperty WidthConstraintProperty;" />
       <MemberSignature Language="ILAsm" Value=".field public static initonly class Xamarin.Forms.BindableProperty WidthConstraintProperty" />