Hero animation bug in Flutter 3.7 - widget is rendered both in flight and at target (duplicated) #121325
Description
Steps to Reproduce
This problem occurred when upgrading from flutter stable 3.3.10 to 3.7.0 and it still persists in flutter 3.7.5. This is reproducible on iOS, Android and Windows, not sure about Mac, Linux and Impeller. This bug does not seem to happen in flutter web - not with html and not with canvaskit.
There may be more cases where this bug exists but I can reproduce it when navigating between two screens and the second screen has a FutureBuilder. When this FutureBuilder renders some kind of loading / waiting state, then the Hero chain is broken so we will not see a hero transition - that's fine. But when we're popping the route and returning to the first screen, the hero animation can be displayed and so it does - except that the widget is rendered both in flight and already at the target position so the hero widget is seen twice. This did not happen in flutter 3.3.10 and it looks weird.
flutter_hero_future_builder.mp4
I have also added a button called Future Builder (completed) and this shows a FutureBuilder where the Future already has a value when rendering the first time. The future builder still starts with "snapshot.hasData = false" so it displays the loading animation for 1 frame and this breaks the hero chain. It would be nice if the FutureBuilder would directly get it's data if the future is completed - that would make future builders more viable so that we can use them in cases where we sometimes need to wait for futures but if the future is already completed, it would just render the child without triggering the loading state of the future builder. Maybe that's a separate feature request but I still wanted to mention it here :)
- Execute
flutter runon the code sample
Expected results: That the Hero animation transitions back when popping the screen from Future Builder screens.
Actual results: That the Hero widget is displayed both at the target position AND also rendering as a transition towards the target position. The same widget is duplicated during the hero transition.
Code sample
Logs
Flutter logs not attached, no relevant information in them.
Flutter analyze:
Analyzing flutter_hero_future_builder...
No issues found! (ran in 1.4s)
Flutter doctor:
[√] Flutter (Channel stable, 3.7.5, on Microsoft Windows [Version 10.0.22000.1574], locale en-SE)
• Flutter version 3.7.5 on channel stable at C:\flutter
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[√] Windows Version (Installed version of Windows is version 10 or higher)
[√] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
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[√] Connected device (3 available)
• Windows (desktop) • windows • windows-x64 • Microsoft Windows [Version 10.0.22000.1574]
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