[android] fix memory leak with CarouselView
#18584
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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
commented
Nov 7, 2023
| { | ||
| public EventHandler<EventArgs> LayoutReady; | ||
| public void OnGlobalLayout() | ||
| class CarouselViewOnGlobalLayoutListener : Java.Lang.Object, ViewTreeObserver.IOnGlobalLayoutListener |
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I made this a nested private class, so it could access the LayoutReady private method.
jonathanpeppers
added
memory-leak 💦
Eilon
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area-controls-collectionview
rmarinho
approved these changes
Nov 8, 2023
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Fixes: #17726
Related: #18365
Adding
CarouselViewto 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
MauiCarouselRecyclerViewdoing:The
ViewTreeObserverlives longer than the page, and so:ViewTreeObserver->CarouselViewwOnGlobalLayoutListenerevent LayoutReady->MauiCarouselRecyclerViewMauiCarouselRecyclerView->CarouselViewCarouselView->Parent.Parent.Parent.*->PageThus the
Pagelives forever.If we remove the
LayoutReadyevent, instead:CarouselViewwOnGlobalLayoutListenersavesMauiCarouselRecyclerViewin a weak reference.It can just call
LayoutReady()directly.MauiCarouselRecyclerViewis able to be GC'd now.MauiCarouselRecyclerView.Dispose()already appropriately will callClearLayoutListener()Lastly,
ViewTreeObserver?.RemoveOnGlobalLayoutListener(_carouselViewLayoutListener)With these changes, the test passes and I don't think anything will leak now. :)
Other changes:
CarouselViewwOnGlobalLayoutListener.