examples/widgets/mixed_viewport.dart crashes when you remove big nodes before small nodes

@HansMuller

Issue by Hixie
Tuesday Aug 25, 2015 at 21:33 GMT
Originally opened as https://github.com/flutter/engine/issues/820

To reproduce:

click add a few times until you have a big block followed by a small block
scroll the big block almost off screen, such that more of the block is off the top of the screen than the height of the small block
tap the big block

The small block is moved off the screen and then there's a crash.

CC @HansMuller

Comment by Hixie
Tuesday Aug 25, 2015 at 21:39 GMT

I think you can also trigger this in examples/widgets/card_collection.dart by flinging a card out while scrolling.

Comment by HansMuller
Tuesday Aug 25, 2015 at 21:52 GMT

I have looked into this (without success) more than once. The failure is signalled by this assert:

'http://localhost:9888/packages/sky/widgets/framework.dart': Failed assertion: line 366 pos 14: 'oldNode.mounted' is not true.

The problem can be avoided by changing MixedViewport._doLayout():

    // Remove any old children.
    for (_Key oldChildKey in childrenByKey.keys) {
      if (!childrenByKey[oldChildKey].mounted)  // HACK
        continue;
      ...
     }

It's not clear how a !mounted Widget ends up in childrenByKey at this point.

Comment by HansMuller
Monday Aug 31, 2015 at 18:25 GMT

I've checked this against the original test case and with the card_collection.dart (swipe away) demo. The bug appears to have been fixed. I haven't been able to pin down exactly which change gets the credit.

Is this still an issue?

I'm going to close this because I don't know how to reproduce it anymore.
I did get #5864 while trying to reproduce it...

Fix build issues with latest boringssl roll. (flutter#144)

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.

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examples/widgets/mixed_viewport.dart crashes when you remove big nodes before small nodes #144

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examples/widgets/mixed_viewport.dart crashes when you remove big nodes before small nodes #144

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FlutterIssues commented on Nov 9, 2015

FlutterIssues commented on Nov 9, 2015

FlutterIssues commented on Nov 9, 2015

sethladd commented on Sep 14, 2016

Hixie commented on Sep 14, 2016

github-actions commented on Aug 17, 2021

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