Disabling lifecycle and shell-based navigation when opening/closing a popup

[pheidler]

Hi, apologies in advance if I'm approaching this problem the wrong way. I'm relatively new to MAUI and shell, having just migrated from Xamarin.Forms and MvvmCross.

Is there a way to disable the lifecycle methods that result from shell navigation when opening and closing a popup? Specifically, OnAppearing, OnDisappearing, and ApplyQueryAttributes? I see the event args in OnNavigatedTo now have an extension method to determine if the previous page was a popup, but what about these other methods?

To provide a little more context, here's an example of why I'm trying to break this pattern:

1. View/ViewModel loads a bunch of data on initial load with parameters passed through ApplyQueryAttributes
2. View/ViewModel opens a small popup
3. Popup is closed, ApplyQueryAttributes is retriggered along with OnAppearing and expensive operation runs a second time

Similarly, say I attach event handlers on OnAppearing and detach them on OnDisappearing. The original view is still visible behind the popup, even if it's not on top of the navigation stack. I want the parent view that opens the popup to still handle events while the popup is open, but obviously this no longer happens if I'm detaching event handlers in the OnDisappearing lifecycle method.

I see a couple of ways around this, none of which are particularly intuitive:

1. Use a combination of flags when calling ShowPopupAsync to selectively enable logic attached to my lifecycle methods. I foresee some gotchas, like if my popup were to contain a link to an entirely different view.
2. Skip the community toolkit popup library entirely and just write my own popup to avoid shell navigation. Downside is no longer being able to take advantage of things like IPopupResult.
3. A magical third option that I've missed that lets popups exist entirely separate from the navigation stack, and keep the current view at the top.

Anyways, let me know if I'm going about this all wrong, or if this is a relatively common problem with an obvious solution. Thanks!

[pictos]

I would recommend to not use (Dis)Appearing on maui, they're very unreliable. It's best to change that to (Un)load events instead.

Sadly we can't changing any of that triggers, since popups are just a modal page doing a modal navigation. So that will trigger those lifecycle events

[stephenquan]

I would (1) add guard to ensure initialize only happens once and when you want it to, (2) post-process the query attributes to prevent locking to UI from heavy operations:

bool _initialized = false;
IDictionary<string, object> _query;
public void ApplyQueryAttributes(IDictionary<string, object> query)
{
    if (!_initialized)
    {
        _initialized = true;
        _query = query;
        Dispatcher.Dispatch(async () => await PostInitializeAsync());
    }
}

async Task PostInitializeAsync()
{
    // Separate query attribute processing to prevent blocking the UI thread.
    // For non-UI operations, consider offloading to a background thread using await Task.Run(/* ... */).
}

If ApplyQueryAttributes is in your view model not on your view, I would recommend passing in the Dispatcher from your View (e.g. ContentPage) to your ViewModel, e.g.

// add this to my view model
public IDispatcher? Dispatcher { get; set; }

// set it from your view (e.g. ContentPage)
viewModel.Dispatcher = Dispatcher;