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missing nullCheck #12068

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missing nullCheck#12068
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Hixie
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frameworkflutter/packages/flutter repository. See also f: labels.
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3: Current Milestone

Description

@JFixby
JFixby
opened on Sep 13, 2017
I: ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
I: The following assertion was thrown during a scheduler callback:
I: There are multiple heroes that share the same tag within a subtree.
I: Within each subtree for which heroes are to be animated (typically a PageRoute subtree), each Hero
I: must have a unique non-null tag.
I: In this case, multiple heroes had the tag "Instance of 'Object'".
I: When the exception was thrown, this was the stack:
I: #0      Hero._allHeroesFor.visitor.<anonymous closure> (package:flutter/src/widgets/heroes.dart:114)
I: #2      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:112)
I: #3      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #4      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #5      ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #6      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #7      MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625)
I: #8      Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #9      MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625)
I: #10     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #11     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #12     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #13     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #14     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #15     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #16     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #17     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #18     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #19     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #20     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #21     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #22     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #23     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #24     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #25     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #26     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #27     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #28     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #29     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #30     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #31     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #32     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #33     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #34     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #35     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #36     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #37     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #38     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #39     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #40     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #41     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #42     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #43     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #44     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #45     List.forEach (dart:core-patch/growable_array.dart:267)
I: #46     SliverMultiBoxAdaptorElement.visitChildren (package:flutter/src/widgets/sliver.dart:866)
I: #47     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #48     MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625)
I: #49     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #50     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #51     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #52     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #53     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #54     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #55     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #56     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #57     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #58     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #59     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #60     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #61     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #62     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #63     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #64     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #65     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #66     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #67     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #68     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #69     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #70     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #71     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #72     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #73     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #74     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #75     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #76     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #77     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #78     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #79     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #80     MultiChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4625)
I: #81     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #82     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #83     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #84     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #85     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #86     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #87     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #88     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #89     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #90     SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:4525)
I: #91     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #92     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #93     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #94     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #95     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #96     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #97     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #98     ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #99     Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #100    ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #101    Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #102    ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #103    Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #104    ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #105    Hero._allHeroesFor.visitor (package:flutter/src/widgets/heroes.dart:126)
I: #106    ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:3591)
I: #107    Element.visitChildElements (package:flutter/src/widgets/framework.dart:2634)
I: #108    Hero._allHeroesFor (package:flutter/src/widgets/heroes.dart:128)
I: #109    HeroController._startHeroTransition (package:flutter/src/widgets/heroes.dart:480)
I: #110    HeroController._maybeStartHeroTransition.<anonymous closure> (package:flutter/src/widgets/heroes.dart:462)
I: #111    BindingBase&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:713)
I: #112    BindingBase&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:657)
I: #113    _invoke (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:86)
I: #114    _drawFrame (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:75)
I: (elided one frame from class _AssertionError)

Activity

  1. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    The given stack trace suggests there's an error in the code, not the framework. Without more details it's not clear what we can do here.

  2. Hixie
    added
    waiting for responseThe Flutter team cannot make further progress on this issue until the original reporter responds
    on Sep 13, 2017

  3. JFixby commented on Sep 13, 2017

    @JFixby
    JFixby
    on Sep 13, 2017
    Author

    You can make the exception more detailed. Now it says "Something happened somewhere' which is not very informative.

  4. JFixby commented on Sep 13, 2017

    @JFixby
    JFixby
    on Sep 13, 2017
    Author

    There is no reference at all to the app code in the stack trace, so this looks like framework problem.

  5. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    I don't know how we could really point you to the right place. We do say "here are multiple heroes that share the same tag within a subtree" and print the offending tag (in this case an object without a useful toString unfortunately).

    What information can we give you that would help here? I'm eager to give you anything you can use...

  6. JFixby commented on Sep 13, 2017

    @JFixby
    JFixby
    on Sep 13, 2017
    Author

    First fix the constructor:

    const FloatingActionButton({
...
    this.heroTag,
...
    • mark heroTag as @required
    • add null check and empty string check on it

    Step two is to add details to the exception:

    • what was the conflicting tag?
    • what are the instances having the same tag? Add detailed .toString() to them and print out their path in the widget tree.

  7. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    Why would FloatingActionButton's hero tag be required? I don't understand.

    The conflicting tag is printed in the logs already. The tags in your case are Object instances so they don't have useful toStrings.

    We can try to print the Hero widget itself; I'm not sure how useful that would be in practice. Let me post a patch to do that.

  8. Hixie
    added
    frameworkflutter/packages/flutter repository. See also f: labels.
    and removed
    waiting for responseThe Flutter team cannot make further progress on this issue until the original reporter responds
    on Sep 13, 2017
  9. Hixie
    added this to the 3: Current Milestone milestone on Sep 13, 2017
  10. Hixie
    self-assigned this
    on Sep 13, 2017

  11. JFixby commented on Sep 13, 2017

    @JFixby
    JFixby
    on Sep 13, 2017
    Author

    Hero tag must be required because framework exception above says ... each Hero must have a unique non-null tag.

    I have no idea what is heroTag, why it is required and why it has to be unique. Also I don't know what is "Instance of 'Object'".

    I can assume that FloatingActionButton constructor swallows default null heroTag and doesn't complain by throwing exception about it. From this point the framework becomes a schrödinger cat. The null circulates somewhere in the framework and gives the mysterious stack-trace above.

  12. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    I don't understand why we are talking about FloatingActionButton. Can you elaborate? What makes you think FloatingActionButton is relevant here?

  13. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    Oh, wait, are you trying to use two FloatingActionButtons on the screen at once?

    I'll post a patch to allow you to set the heroTag to null so that you can do that. In the meantime, you can just set heroTag to a different value on each FloatingActionButton if you want to do that. Generally speaking having multiple FloatingActionButtons on the screen is considered bad UI.

  14. Hixie commented on Sep 13, 2017

    @Hixie
    Hixie
    on Sep 13, 2017
    Contributor

    #12074

  15. 2 remaining items

  16. mklim
    added a commit that references this issue on Sep 11, 2019

    Manual roll of engine 7ea9884...5b94c8a (#40275)

    0de6fc8
  17. mklim
    added a commit that references this issue on Sep 12, 2019

    Roll engine from 7ea9884..3c6383f (77 commits 🔥) (#40372)

    d4b1f49
  18. aam
    added a commit that references this issue on Sep 12, 2019

    Roll engine to 6e6de94

    0cd7b26
  19. mklim
    added a commit that references this issue on Sep 13, 2019

    Roll engine to 6e6de94 (#40394)

    c37d06c
  20. mklim
    added a commit that references this issue on Sep 13, 2019

    Roll engine 7ea9884..1b63444 (91 commits 🔥🔥🔥) (#40442)

    8d23bcf
  21. Inconnu08
    added 4 commits that reference this issue on Sep 30, 2019

    Manual roll of engine 7ea9884...5b94c8a (flutter#40275)

    1c97731

    Roll engine from 7ea9884..3c6383f (77 commits 🔥) (flutter#40372)

    fcec123

    Roll engine to 6e6de94 (flutter#40394)

    1d6b845

    Roll engine 7ea9884..1b63444 (91 commits 🔥🔥🔥) (flutter#40442)

    a4280e3

  22. github-actions commented on Sep 4, 2021

    @github-actions
    github-actionsbot
    on Sep 4, 2021

    This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

  23. github-actions
    locked as resolved and limited conversation to collaborators on Sep 4, 2021
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