Popup V2 Not Working in Production

[david-maw]

This is a continuation of a question which I put in the wrong place; however it repeats essentially everything there so there's no need to look at the original.

I set out to convert my popups to V2, built a testbed and tried the new versions of several popups out. Got all that working fine, then moved the code to my production program and they simply do not work. Nothing shows up and they hang indefinitely on the await, To debug it I thought I'd try something simple strictly in line:

            await this.ShowPopupAsync(new Label
            {
                Text = "This must be dismissed manually",
                BackgroundColor = Colors.Red,
                VerticalOptions = LayoutOptions.End
            }, new PopupOptions
            {
                CanBeDismissedByTappingOutsideOfPopup = true,

                Shape = new RoundRectangle
                {
                    CornerRadius = new CornerRadius(20, 20, 20, 20),
                    StrokeThickness = 2,
                    Stroke = Colors.LightGray
                }
            });

Even this shows nothing and waits indefinitely.

While it works fine in my testbed, in the production code using the same environment it shows nothing and the await waits indefinitely. This happens in a debug build on both Windows and Android. I've tried clean and even gone as far as exiting VS, removing obj and bin folders, then restarting it, all to no avail. I copied over as much project configuration as seemed relevant to be sure my testbed was as close to the production app as possible.

I presume the NuGet packages are ok because they work fine in the testbed, although there are a lot more in the production app that are not used in the testbed. I can see net9.0-windows10.0.19041.0\win10-x64\CommunityToolkit.Maui.Core.dll being loaded, which seems encouraging but when the application stops, I just have 18 threads in external code, which is a bit overwhelming.

Has anyone got any ideas, either of how to fix it, or how to debug it further? Thanks.

[MartyIX]

Has anyone got any ideas, either of how to fix it, or how to debug it further? Thanks.

I guess that a first step may be to test if the PopupOptions are to blame. Or even a step furthen, can you achieve showing a popup at all or not?

btw: Another thing that comes to mind immediately - are you on the UI thread?

[david-maw]

Same failure when passing PopupOptions.Empty or null, I can't show a V2 popup at all in my real app, even though the exact same code works fine in my testbed. The production calls are in all the same places that worked before with the earlier Popup implementation) so I'm pretty confident I'm on the UI thread. Just to be sure I tried explicitly running on the UI thread:

            await MainThread.InvokeOnMainThreadAsync(async () =>
            {
                await this.ShowPopupAsync(new Label
                {
                    Text = "This must be dismissed manually",
                    BackgroundColor = Colors.Red,
                    VerticalOptions = LayoutOptions.End
                });
            });

Has the same outcome (no display, waits indefinitely). I popped the same code into the testbed where of course it worked fine, sigh. Next step I can think of is to strip stuff out of the production App until it starts to work.

[david-maw]

I'd have expected an uncaught exception error if there was one, but I inserted a local try/catch to see if it triggered, it didn't, just waited indefinitely on the await as before.

Of the 18 threads none really cried out to me as being obviously problematic, just looked like a program doing an `await' to me, but I'm not particularly familiar with what it should look like. Comparing it with the testbed in the same state it looked pretty similar though.

[MartyIX]

Next step I can think of is to strip stuff out of the production App until it starts to work.

Unfortunately, that sounds about right :(

Perhaps before jumping to that, it might be good to check packages.lock.json file (this should generate it) for your MAUI project if the resolved dependencies are really as they should be.

[MartyIX]

I'd have expected an uncaught exception error if there was one, but I inserted a local try/catch to see if it triggered, it didn't, just waited indefinitely on the await as before.

Another perspective: Isn't it possible that the popup is displayed but it's just hidden behind (in the Z dimension sense) your other stuff?

[david-maw]

I'm pretty sure it wasn't a Z-Order problem because the first test dialog I tried would auto-close in 5 seconds, so the await would have continued.

A bit of good news though, I moved the call earlier in my prgram and it worked so now all I have to do is a binary search between where it worked and where it stops working. I'll report back when I know more.

[david-maw]

Nailed it, as expected it was something fairly silly, the offending code was:

Shell.Current.Navigating += Cancel_Navigation;

Which does exactly what you imagine it might. It's old code meant to prevent the user from navigating away from a splash page (the page has no UI, but using the Android 'back' gesture, for example). The initial attempts to use Popups in my production code were all in the scope of that statement and messing with Shell navigation now affects popups. I'll just come up with an alternative for that code and life's good. Thanks for spending time on this, I appreciate your help.

[bijington]

Oh great spot! That is exactly what I was hoping for! Now to make it possible to use with the toolkit as PopupPage is currently internal

[david-maw]

@bijington I'm back and still have not been able to persuade OnAppearing to get called when switching between apps. I've only tried Android and Windows though. Can you give me a few more hints on making this happen?

Thanks @pictos for spotting 28384, with a bit of help from the toolkit that would clean up my "are you navigating to/from a popup" test considerably.

[bijington]

Perhaps I'm mistaken or things have changed. Although one example that comes to mind is when you request permissions in iOS. I believe your app will 'appear' again after the request prompt is responded to by the user

[david-maw]

I have a nagging feeling that things may indeed have changed, though perhaps I'm just remembering earlier warnings about when OnAppearing is called.

I've seen similar behavior to what you describe on Android when switching to an OAuth authorization screen or requesting permissions. It seems like if the app shows a different page, you get a call on OnAppearing when it switches back. The key point is that the app must do something (like request permissions) to trigger this, the user can't make it happen simply by switching apps. This isn't just academic, it means is that an app can predict when it's susceptible to leaving a page (having OnDisapearing called) and returning to it (with OnAppearing called). With popup V2, showing a popup is now one of the things that creates this situation and that can create surprises if you're not expecting it (in my case it mostly didn't, and even when it did, fixing them was less than 40 hours work). From what I can see the new implementation is enough of an improvement that it is worth the migration effort and merely knowing this happens takes much of the debugging pain away. That means this is merely a argument for documenting the "page switch on popup" behavior.

[bijington]

Thanks for this. I'll make an effort to get this documented over the weekend