RefreshView: add new internal property IsRefreshAllowed to fix xamarin#14350

Platform renderers can use IsRefreshAllowed to disable swipe to refresh in a
controlled fashion - letting any pending refresh/command finish first to
avoid that ongoing refresh indication is stopped prematurely (even if
the refresh command is still executing).

Author: cpraehauso

Xamarin.Forms.Core/RefreshView.cs

@@ -1,4 +1,5 @@
 using System;
+using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Windows.Input;
 using Xamarin.Forms.Platform;
@@ -49,6 +50,9 @@ static object OnIsRefreshingPropertyCoerced(BindableObject bindable, object valu
 			if (!view.IsEnabled)
 				return false;
 
+			if (!view.IsRefreshAllowed)
+				return false;
+
 			if (view.Command == null)
 				return value;
 
@@ -98,12 +102,22 @@ public object CommandParameter
 			set { SetValue(CommandParameterProperty, value); }
 		}
 
+		public static readonly BindableProperty IsRefreshAllowedProperty =
+			BindableProperty.Create(nameof(IsRefreshAllowed), typeof(bool), typeof(RefreshView), false, BindingMode.TwoWay);
+
+		[EditorBrowsable(EditorBrowsableState.Never)]
+		public bool IsRefreshAllowed
+		{
+			get { return (bool)GetValue(IsRefreshAllowedProperty); }
+			set { SetValue(IsRefreshAllowedProperty, value); }
+		}
+
 		void RefreshCommandCanExecuteChanged(object sender, EventArgs eventArgs)
 		{
 			if (Command != null)
-				SetValueCore(IsEnabledProperty, Command.CanExecute(CommandParameter));
+				SetValueCore(IsRefreshAllowedProperty, Command.CanExecute(CommandParameter));
 			else
-				SetValueCore(IsEnabledProperty, true);
+				SetValueCore(IsRefreshAllowedProperty, true);
 		}
 
 		public static readonly BindableProperty RefreshColorProperty =

Xamarin.Forms.Platform.Android/Renderers/RefreshViewRenderer.cs

@@ -57,6 +57,9 @@ public override bool Refreshing
 					RefreshView.SetValueFromRenderer(RefreshView.IsRefreshingProperty, _refreshing);
 
 				base.Refreshing = _refreshing;
+
+				// Allow to disable SwipeToRefresh layout AFTER refresh is done
+				UpdateIsEnabled();
 			}
 		}
 
@@ -140,8 +143,16 @@ void UpdateColors()
 		}
 
 		void UpdateIsRefreshing() => Refreshing = RefreshView.IsRefreshing;
-
-		void UpdateIsEnabled() => SwipeRefreshLayout.Enabled = RefreshView.IsEnabled;
+		
+		void UpdateIsEnabled()
+		{
+			// NOTE: only disable while NOT refreshing, otherwise Command bindings CanExecute behavior will effectively
+			// cancel refresh animation. If not possible right now we will be called by UpdateIsRefreshing().
+			// For details see https://github.com/xamarin/Xamarin.Forms/issues/14350
+			var isEnabled = RefreshView.IsEnabled && RefreshView.IsRefreshAllowed;
+			if (isEnabled || !SwipeRefreshLayout.Refreshing)
+				SwipeRefreshLayout.Enabled = isEnabled;
+		}
 
 		bool CanScrollUp(AView view)
 		{
@@ -207,6 +218,8 @@ void HandlePropertyChanged(object sender, PropertyChangedEventArgs e)
 				UpdateContent();
 			else if (e.PropertyName == VisualElement.IsEnabledProperty.PropertyName)
 				UpdateIsEnabled();
+			else if (e.PropertyName == RefreshView.IsRefreshAllowedProperty.PropertyName)
+				UpdateIsEnabled();
 			else if (e.PropertyName == RefreshView.IsRefreshingProperty.PropertyName)
 				UpdateIsRefreshing();
 			else if (e.IsOneOf(RefreshView.RefreshColorProperty, VisualElement.BackgroundColorProperty, VisualElement.BackgroundProperty))

Xamarin.Forms.Platform.UAP/RefreshViewRenderer.cs

@@ -105,6 +105,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 				UpdateContent();
 			else if (e.PropertyName == VisualElement.IsEnabledProperty.PropertyName)
 				UpdateIsEnabled();
+			else if (e.PropertyName == RefreshView.IsRefreshAllowedProperty.PropertyName)
+				UpdateIsEnabled();
 			else if (e.PropertyName == RefreshView.IsRefreshingProperty.PropertyName)
 				UpdateIsRefreshing();
 			else if (e.PropertyName == RefreshView.RefreshColorProperty.PropertyName)
@@ -135,7 +137,7 @@ void UpdateContent()
 
 		void UpdateIsEnabled()
 		{
-			Control.IsEnabled = Element.IsEnabled;
+			Control.IsEnabled = Element.IsEnabled && Element.IsRefreshAllowed;
 		}
 
 		void UpdateIsRefreshing()

Xamarin.Forms.Platform.iOS/Renderers/RefreshViewRenderer.cs

@@ -81,6 +81,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 
 			if (e.PropertyName == VisualElement.IsEnabledProperty.PropertyName)
 				UpdateIsEnabled();
+			else if (e.PropertyName == RefreshView.IsRefreshAllowedProperty.PropertyName)
+				UpdateIsEnabled();
 			else if (e.PropertyName == RefreshView.IsRefreshingProperty.PropertyName)
 				UpdateIsRefreshing();
 			else if (e.IsOneOf(RefreshView.RefreshColorProperty, VisualElement.BackgroundColorProperty))
@@ -252,7 +254,7 @@ void UpdateIsRefreshing()
 
 		void UpdateIsEnabled()
 		{
-			bool isRefreshViewEnabled = Element.IsEnabled;
+			bool isRefreshViewEnabled = Element.IsEnabled && Element.IsRefreshAllowed;
 			_refreshControl.Enabled = isRefreshViewEnabled;
 
 			UserInteractionEnabled = true;