Commits on Nov 7, 2023

1. [android] fix memory leak with CarouselView …

   Fixes: dotnet#17726
   
   Adding `CarouselView` to a page and navigating away from it keeps the
   page alive forever on Android. I was able to reproduce this in a test.
   
   It took me a while to actually track this one down, but the problem
   boils down to `MauiCarouselRecyclerView` doing:
   
       _carouselViewLayoutListener = new CarouselViewwOnGlobalLayoutListener();
       _carouselViewLayoutListener.LayoutReady += LayoutReady;
       ViewTreeObserver.AddOnGlobalLayoutListener(_carouselViewLayoutListener);
   
   The `ViewTreeObserver` lives longer than the page, and so:
   
   * `ViewTreeObserver` -> `CarouselViewwOnGlobalLayoutListener`
   * `event LayoutReady` -> `MauiCarouselRecyclerView`
   * `MauiCarouselRecyclerView` -> `CarouselView`
   * `CarouselView` -> `Parent.Parent.Parent.*` -> `Page`
   
   Thus the `Page` lives forever.
   
   If we remove the `LayoutReady` event, instead:
   
   * `CarouselViewwOnGlobalLayoutListener` saves `MauiCarouselRecyclerView`
   in a weak reference.
   
   * It can just call `LayoutReady()` directly.
   
   * `MauiCarouselRecyclerView` is able to be GC'd now.
   
   * `MauiCarouselRecyclerView.Dispose()` already appropriately will call
     `ClearLayoutListener()`
   
   * Lastly, `ViewTreeObserver?.RemoveOnGlobalLayoutListener(_carouselViewLayoutListener)`
   
   With these changes, the test passes and I don't think anything will leak
   now. :)
   
   Other changes:
   
   * I fixed the typo in `CarouselViewwOnGlobalLayoutListener`.
   * I sorted the type names in the test alphabetically.

   

   jonathanpeppers committed Nov 7, 2023
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