Page weak reference is still alive after pushing and popping pages modally or normally

[MDThomsen]

Description

Taking inspiration from this guide from Jonathan Peppers I wanted to investigate why I am experiencing memory increases over time when pushing and popping pages both modally and normally.

I am setting up a weak reference to the page that I am pushing, and then popping. After popping I am performing a GC.Collect(), but I notice that the weak reference is still alive afterwards. I would assume that the weak reference would no longer be alive after popping the page from the view hierarchy.

Code sample:

WeakReference pageReference;

{
     var page = new MainPage("New Modal");
     pageReference = new WeakReference(page);

     await Navigation.PushModalAsync(page);
     await Navigation.PopModalAsync();
}

await Task.Yield();
GC.Collect();
GC.WaitForPendingFinalizers();

Console.WriteLine($"Page still alive: {pageReference?.IsAlive}");

Otherwise please check out the linked sample repo.

Steps to Reproduce

1. Create a weak reference to a page and push it normally or modally within it's own scope.
2. Pop the page
3. Call Garbage Collector
4. Check if the weak reference is still alive. (It is)

Link to public reproduction project repository

https://github.com/MDThomsen/Weak-Reference-MAUI-Sample/

Version with bug

8.0.6 SR1

Is this a regression from previous behavior?

No, this is something new

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 14

Did you find any workaround?

No response

Relevant log output

No response

[dalux-era]

We encountered a similar issue. Seeing a lot of memory leaks, especially using NavigationPage

[mattleibow]

@jonathanpeppers thoughts?

[jonathanpeppers]

@MDThomsen do can you record a .gcdump file of when it has leaked like this?

We just recently revamped Android instructions here:

• https://github.com/xamarin/xamarin-android/blob/main/Documentation/guides/tracing.md
• https://github.com/xamarin/xamarin-android/blob/main/Documentation/guides/tracing.md#memory-dumps-for-android-in-net-8

[jonathanpeppers]

Oh, if the sample uses TabbedPage it might be the same as this one:

• [regression/8.0.0] Navigating back from a TabbedPage does not invoked a destructor #17959

https://github.com/MDThomsen/Weak-Reference-MAUI-Sample/blob/main/Sample/Sample/Sample/ExtendedTabbedPage.cs

[MDThomsen]

@jonathanpeppers Here is the attached gcdump, where the ContentPage is getting pushed and popped ten times in a row.
20240313_084013_42800.zip

Yeah, I forgot to make some more concise names for the pages. The MainPage, set in the App.xaml.cs, is a TabbedPage which has one child, which is a ContentPage, that pushes and pops a copy of itself.

[jonathanpeppers]

@MDThomsen can you try the latest "nightly build"?

• https://github.com/dotnet/maui/wiki/Nightly-Builds

8.0.20-nightly.10336, for example has a fix for TabbedPage on Android: 2317119

[dotnet-policy-service]

Hi @MDThomsen. We have added the "s/try-latest-version" label to this issue, which indicates that we'd like you to try and reproduce this issue on the latest available public version. This can happen because we think that this issue was fixed in a version that has just been released, or the information provided by you indicates that you might be working with an older version.

You can install the latest version by installing the latest Visual Studio (Preview) with the .NET MAUI workload installed. If the issue still persists, please let us know with any additional details and ideally a reproduction project provided through a GitHub repository.

This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.