[MISSING DEPRECATION] Non-firing function overrides like OnMeasure and OnAppearing should be marked as deprecated

[janne-hmp]

Description

In .NET MAUI 9.0 Preview 2.0, there are several overrideable function such as OnMeasure and OnAppearing (for content pages) that do not fire anymore. If they are intended to be deprecated, they should be marked accordingly with a remark that they do not fire in MAUI, as opposed to Xamarin.

Steps to Reproduce

No response

Link to public reproduction project repository

No response

Version with bug

9.0.0-preview.1.9973

Is this a regression from previous behavior?

Yes, this used to work in Xamarin.Forms

Last version that worked well

Unknown/Other

Affected platforms

iOS, Android, I was not able test on other platforms

Affected platform versions

No response

Did you find any workaround?

Yes, using still firing events.

Relevant log output

No response

[jfversluis]

Could you please provide a sample of what you are trying to do and wat isn't work?

[janne-hmp]

First, I was using in Xamarin override OnMeasure of SKCanvasView to make it autosizing. OnMeasure does not fire anymore in Maui for SKCanvasView, and there is a new MeasureOverride function, that fires instead (yet is bugged, but that is a separate topic). It is not obvious coming from Xamarin that OnMeasure does not fire, so it would be great that there would be a warning saying so (being deprecated in Maui).

Second, in Xamarin, I was using overring OnAppearing function for a content page as follows:

        protected override void OnAppearing()
        {
            base.OnAppearing();
            if(_gamePage.PlayingReplay)
            {
                if(!string.IsNullOrWhiteSpace(_replayEnteredName))
                {
                    Device.StartTimer(TimeSpan.FromMilliseconds(GHConstants.ReplayAskNameDelay1), () =>
                    {
                        ReplayDoEnterName();
                        return false;
                    });
                }
            }
            else
            {
                eName.Focus();
            }
        }

However, it turns out that OnAppearing does not fire in Maui, which would be great to get a warning about. Instead, you have to use ContentPage_Appearing event or ContentPage_Loaded event. So in Maui, the code is now as follows:

        public NamePage()
        {
            InitializeComponent();
            Loaded += ContentPage_Loaded;
        }

        private void ContentPage_Loaded(object sender, EventArgs e)
        {
            if (_gamePage.PlayingReplay)
            {
                if (!string.IsNullOrWhiteSpace(_replayEnteredName))
                {
                    var timer = Microsoft.Maui.Controls.Application.Current.Dispatcher.CreateTimer();
                    timer.Interval = TimeSpan.FromSeconds(UIUtils.GetWindowHideSecs());
                    timer.IsRepeating = false;
                    timer.Tick += (s, e) => { ReplayDoEnterName(); };
                    timer.Start();
                }
            }
            else
            {
                eName.Focus();
            }
        }

[PureWeen]

We obsoleted a number of OnMeasure methonds in net9

OnAppearing should still work Can you attach a repro?

We have a bunch of tests that would be failing right now if OnAppearing stopped working

[janne-hmp]

I tested this now again in .NET MAUI 9.0 RC1, and OnAppearing indeed seems to be working now fine. There was some problem there in Preview 2, but it seems to have been fixed now. I will close the issue.