Description

On Android 11 and lower, the back button on the home page has different behaviour from the home button - it finishes the current activity. This was changed on Android 12 (see this page), however on earlier versions, this results in a different behaviour.

This, however, means that pressing back, then re-opening the app causes Blazor to dispose of resources during app initialization when the app has re-opened. This means the WebView has already been disposed of, or not yet initialized - I'm not quite sure which one. This causes any DisposeAsync() calls against IJSObjectReference objects to hang synchronously.

Steps to Reproduce

1. Create a new MAUI app
2. Create a simple site.js file in wwwroot
3. Create the following service class:

public class TestJsReferenceService : IAsyncDisposable {
        private readonly IJSRuntime jsRuntime;
        private IJSObjectReference? module = null;
        private const string SomeJsModule = "/site.js";
        public TestJsReferenceService(IJSRuntime jsRuntime)
        {
            this.jsRuntime = jsRuntime;
        }

        public async Task LoadModuleAsync(CancellationToken cancellationToken = default)
        {
            module = await jsRuntime.InvokeAsync<IJSObjectReference>(
                "import", cancellationToken, SomeJsModule);
        }

        public async ValueTask DisposeAsync()
        {
            if (module is not null)
            {
                // The app hangs here
                await module.DisposeAsync();
            }
        }
}

4. Register the above service as Transient or Scoped
5. Inject the dependency into any page or component and call LoadModuleAsync()
6. Deploy the project to Android 11 or earlier and make sure LoadModuleAsync() is called. Note: Any other JS invoke function could work so long as we're left with an IJSObjectReference
7. Exit the application with the back button, then reopen it from the app list
8. The app hangs on the loading screen

Link to public reproduction project repository

https://github.com/kanadaj/MauiHangRepro

Version with bug

7.0 (current)

Last version that worked well

7.0 (current)

Affected platforms

Android

Affected platform versions

Android 11 and down

Did you find any workaround?

The only workaround we've found is tying IJSObjectReference lifecycle to their holding component if they aren't on the home page. No idea about the home page. This also breaks most existing Blazor libraries on Android 11 and under.

Relevant log output

No response