Picker not working on macOS

[andrewstellman]

Description

The Picker control seems to be broken on macOS.
On macOS, clicking on the Picker displays a dialog that shows the title and a "Done" button but doesn't display the items:

Here's a video that shows it in action:

ReproduceMauiPickerIssue.mov

I'm running it on the latest 8.0 GA SDK:

andrewstellman@Andrews-MBP reproduce-maui-picker-issue % dotnet workload list

Installed Workload Id      Manifest Version      Installation Source
--------------------------------------------------------------------
maui                       8.0.7/8.0.100         SDK 8.0.200        

Use `dotnet workload search` to find additional workloads to install.

andrewstellman@Andrews-MBP reproduce-maui-picker-issue % dotnet build -t:Run -f net8.0-maccatalyst

Welcome to .NET 8.0!
---------------------
SDK Version: 8.0.203

This same code works fine on Windows and Android:

Windows:

Android:

Steps to Reproduce

Here's some simple code to reproduce the issue:

XAML

            <Picker x:Name="BirdPicker" Title="Pick a bird" />

            <Button x:Name="AddBird" Text="Add a bird"
                Margin="0,0,0,20" SemanticProperties.Hint="Adds a bird"
                Clicked="AddBird_Clicked"/>

            <Label x:Name="Birds"
                    Padding="10" MinimumWidthRequest="150"
                    TextColor="White" BackgroundColor="DarkBlue" 
                    SemanticProperties.Description="Shows the added birds" />

C#

	public MainPage()
	{
		InitializeComponent();

		BirdPicker.ItemsSource = new List<string> {
			"Duck",
			"Pigeon",
			"Penguin",
			"Ostrich",
			"Owl"
		};
	}

	private void AddBird_Clicked(object sender, EventArgs e)
	{
		if (!String.IsNullOrEmpty(Birds.Text))
		{
			Birds.Text = Birds.Text + Environment.NewLine;
		}
		Birds.Text += BirdPicker.SelectedItem;
	}

Link to public reproduction project repository

https://github.com/andrewstellman/reproduce-maui-picker-issue/

Version with bug

8.0.3 GA

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

Unknown/Other

Affected platforms

macOS

Affected platform versions

No response

Did you find any workaround?

No response

Relevant log output

No response

[drasticactions]

Duplicate of #18015

In short, the way the picker is constructed on Catalyst makes it very fragile. It consists of an inline text input field that spawns a UIAlert with a picker control inside it, and that UIPicker has no height. If you remove the title, that "fixes" the constraints on the hacked-in UIPicker and lets it show its items.

It doesn't affect other platforms because they use more traditional pickers. The underlying implementation for Catalyst should need to be fixed.

[ninachen03]

Verified this issue with Visual Studio for mac 17.6.10(build428) (MauiVersion 8.0.14 & 8.0.0.-rc.2.9530). Can not repro this issue on maccatalyst.

[drasticactions]

@ninachen03 The issue is that the picker items do not appear. You're only seeing the title of the alert, but not the items that should be shown within it. Removing the title from the picker will show the items. The bug is still there.

[andrewstellman]

@drasticactions thanks so much for out the workaround. This was going to be a really annoying issue for the 5th edition of Head First C#, which I'm just finishing up. At least now I can find a way to give people a way to get their code working!

We're in production, so hopefully I can fix the code before we go to press so I don't have to have them print a warning that says "Mac readers - there's a bug that keeps the Picker from working if the Title property is set." Seems a little unfortunate that the issue is closed as not planned. 😢

[drasticactions]

@andrewstellman It was closed as a duplicate of the issue I linked to, which is the same as yours, and is still open. That issue has this listed as a "regression" but it's complicated: the code itself for the picker didn't change. I believe it's macOS specific where a version bump "broke" this implementation (so if you run this on earlier versions of macOS, it should "work" correctly).

I say this in quotes because, IMO (I'm not on the MAUI team, I'm in .NET and work on other tooling within VS to help .NET MAUI, such as Hot Reload. I triage issues and give help where I can), because I think this implementation is very hacky (Implementing a UIAlert that to then jam in a UIPicker) that "works" but is not ideal to do.

So it can be "fixed," (most likely by trying to figure out why the UI constraints are broken and the picker is hidden) but I honestly think it needs to be redone for Mac Catalyst. Mainly because if you enable the Desktop Idiom for Mac Catalyst, this picker will blow up your app, because UIPicker doesn't exist in Mac Catalyst with the Desktop idiom enabled (As in, a UIKit limitation. You can't use it in normal Catalyst apps in any language with Desktop mode enabled) and will actively throw an exception saying not to use it.

[andrewstellman]

Ah, fantastic—my bad, I misunderstood. I'm in touch with several folks on the MAUI team, I'm sure they want to make sure the Picker control works correctly for Mac.