[Bug] Alerts currently don't work if you call them from the constructor

[PureWeen]

Description

If you call DisplayAlert from the constructor of a page it currently does not work on WinUI

Go to the alerts page and add a call to DisplayAlert from the ctor

public AlertsPage()
{
      DisplayFromCtor();
}

async void DisplayFromCtor() =>  await DisplayAlert();

[hartez]

In Forms calling alerts from the constructor would put them in a queue that would be processed after Appearing; maybe the queue stuff didn't get ported?

[Eilon]

There's a dup here suggesting maybe we shouldn't support it: #4336

[jamesmontemagno]

IMHO this should not be a supported scenario that could be documented. The UI isn't visible yet, you basically shouldn't do anything in your constructor.

[Eilon]

I'm guessing people do it because it's the logical equivalent of printf debugging. No strong opinion on whether it should be allowed.

[PureWeen]

Another use case here is that the ctor is the easiest place for an alert you only want to show on the first load of a page. In theory you could check for this case in "Appearing" but it's a bit more code and since the ctor works then why not just put it there.

[jamesmontemagno]

We could introduce a "FirstLoad" type of thing like blazor... so you ahve OnAPpearing that happens eveyr time, but OnFirstLoad or something that is after the screen loads for teh first time?

[shimingsg]

Not reproducible with Android 11.

[Eilon]

Re-opening because I'm not sure if this is the right behavior on all platforms, even if perhaps it works on Android.

[Eilon]

The dup bug specifically mentioned that it doesn't work on Windows: #4336

[jsuarezruiz]

Testing with RC3 and main branch, this is now working:

Reviewing the history have been fixed by the commit fffaae1.