[Bug] ListView RefreshCommand ActivityIndicator does disappear on Android if CanExecute is changed to false

[kwintAl]

Description

A Command is used in a ToolbarItem.Command and in a ListView.RefreshCommand. The Command starts a Bluetooth discovery and is disabled (CanExecute returns false) while the discovery is running.

In case the command is executed via ToolbarItem the ActivityIndicator appears on screen.
In case the command is executed via ListView.RefreshCommand(PullToRefresh) the ActivityIndicator disappears when CanExecute is changed to false.

It looks like ListView.RefreshAllowed is set to false

  void OnCommandCanExecuteChanged(object sender, EventArgs eventArgs)
  {
  	RefreshAllowed = RefreshCommand.CanExecute(null);
  }

and this causes SwipeRefreshLayout.Enabled = false

  void UpdateIsSwipeToRefreshEnabled()
  {
  	if (_refresh != null)
  		_refresh.Enabled = Element.IsPullToRefreshEnabled && (Element as IListViewController).RefreshAllowed;
  }

From Xamarin documentation:

When defining a RefreshCommand, the CanExecute method of the command can be specified to enable or disable the command.

Is that the desired behavior? If yes, why do I need additional properties IsPullToRefreshEnabled and IsRefreshing?

I think CanExecute should be checked to avoid executing a Command twice but the ActivityIndicator should not disappear. For this logic we have the IsRefreshing property.

My current workaround:

using System.ComponentModel;
using Mono.Device.Discovery.Example.Android;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(ListView), typeof(ListRenderer))]
namespace Mono.Device.Discovery.Example.Android
{
	public class ListRenderer : ListViewRenderer
	{
		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			
			if (e.PropertyName == nameof(ListView.RefreshAllowed))
			{
				return;
			}
			base.OnElementPropertyChanged(sender, e);
		}
	}
}

Steps to Reproduce

1. Create a Command
2. PullToRefresh
3. Command should return CanExecute false
4. ActivityIndicator disappears

Expected Behavior

ActivityIndicator is visible

Actual Behavior

ActivityIndicator is not visible

Basic Information

• Version with issue:
• Last known good version:
• IDE: Rider 2019.2.3
• Platform Target Frameworks:
  • iOS:
  • Android: 9.0 API 28
  • UWP:
• Android Support Library Version:
• Nuget Packages: Xamarin.Forms 4.3.0.947036
• Affected Devices:

Screenshots

Reproduction Link

[hartez]

Yep. If CanExecute changes while the refresh indicator is up, the indicator disappears. Seems like it should wait until the Command is finished.

_8384 Repro.zip