Visibility not restored for Hero after pop

[hahafather007]

After clicking the Hero widget to jump to a list page, scroll down the list until the Hero widget of the corresponding tag leaves the screen and then return to the page. The Hero widget of the previous page will be blank. This is a very serious problem, and now our online project has been plagued by this problem.


Flutter version:

[✓] Flutter (Channel beta, v1.7.8+hotfix.4-pre.7, on Mac OS X 10.14.6 18G87,
    locale zh-Hans-CN)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
[✓] Android Studio (version 3.5)
[!] IntelliJ IDEA Community Edition (version 2019.2.1)
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
[✓] Connected device (1 available)

Reproduce code like this:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: GestureDetector(
          onTap: () {
            Navigator.of(context).push(MaterialPageRoute(builder: (context) {
              return Scaffold(
                body: ListView(
                  children: <Widget>[
                    Center(
                      child: Hero(
                        tag: "111",
                        child: Container(
                          width: 50,
                          height: 50,
                          color: Colors.blue,
                        ),
                      ),
                    ),
                    Container(
                      height: 2000,
                    ),
                  ],
                ),
              );
            }));
          },
          child: Hero(
            tag: "111",
            child: Container(
              width: 50,
              height: 50,
              color: Colors.blue,
            ),
          ),
        ),
      ),
    );
  }
}

[hahafather007]

@ianloic @anaisbetts @sgraham @sethladd

[goderbauer]

@chunhtai This may be caused by your change in #37341. Maybe you can take a look?

[LongCatIsLooong]

@goderbauer It's probably not introduced in that PR. We didn't handle the case where fromHero is null so the hero transition technically lasts forever. Working on a fix now.

[goderbauer]

But prior to that PR we would restore the visibility of the from Hero once the flight is completed so it would always be visible when you do the pop, no?

[LongCatIsLooong]

Sorry I phrased it poorly. We set offstage to false when the animation finishes (i.e. in an animation status change callback) but there's no animation to begin with because the fromHero is null (garbage collected by the ListView).

[chunhtai]

I wonder what is the expected behavior of this situation
There are two possible scenarios.
1, the fromHero is destroyed
2, the fromHero is keptalive but outside viewport.

[LongCatIsLooong]

My original plan was to fade in the toHero (since we're fading out the hero if the flight is aborted) but it doesn't look as good as I expected because the hero OverlayEntry is the topmost OverlayEntry, so it's entirely visible during the transition, even when the from route overlaps with it. So I'm planning to end the hero transition right away if fromHero is null. Thoughts?

[chunhtai]

@LongCatIsLooong I think ending it if fromHero is null make sense. What about the fromHero is keptalive, will the hero transition trigger in this case?

[nekocode]

We met the same problem. Hope you guys can fix it soon. Otherwise we can only downgrade the flutter sdk.

[LongCatIsLooong]

@chunhtai it produces an interesting animation, but that seems to be a benigner bug. Created #40307.

[LongCatIsLooong]

Oh I didn't realize #37341 keeps the original Hero invisible.

[dshukertjr]

Why is this issue closed? It is not solved.

[LongCatIsLooong]

@dshukertjr are you using the master channel? If you are and the issue is still reproducible, could you provide a minimal repro?

[dshukertjr]

@LongCatIsLooong No, I'm using the stable channel. Is the issue solved in the master channel?

[LongCatIsLooong]

@dshukertjr it should be. The issue was closed because #40306 was merged.

[aleksandar-radivojevic]

This issue is not solved in 1.9.1+hotfix.4 !!!!

[vitor-gyant]

@LongCatIsLooong I'm still facing this issue on stable branch version 1.9.1+hotfix4. Could you please double check if the issue is solved in this version ? Thanks.

[LongCatIsLooong]

@vitor-gyant it is not in 1.9.1. The earliest version with the fix is v1.10.4: 6430012.

[vitor-gyant]

@LongCatIsLooong I see. Any plans to cherry pick it to 1.9 on the stable branch ?

[LongCatIsLooong]

Unfortunately, not that I know of. You could try applying the patch locally, or consider switching to beta/dev/master: https://github.com/flutter/flutter/wiki/Flutter-build-release-channels.

[iassal]

This caused a severe regression in our app as we use hero animations for input fields. Had to deprecate all pop calls as a hotfix

[LongCatIsLooong]

/cc @tvolkert for the hotfix request. See also the duplicates of this issue.

[LongCatIsLooong]

FYI the hotfix request is being evaluated.

[vitor-gyant]

@tvolkert Hot fix is a must for us, at least. Keeping a fork of the flutter repo just to be able to apply the cherry pick creates a big maintenance issue. Moreover, our app uses several hero animations in the primary flows and now they simply don't work and the visual impact is a blocker for the release.

We've started the migration process to the master branch but it will take time to finish plus the QA rounds. Since we also have app2app changes on master this will slow down us for a while if the hot fix is not approved.

[chickenblood]

What is the status of this? Is there a workaround? This bug is affecting my new app which I hoped to get out on December 1. It seems like a common pattern that would affect many apps.

[chickenblood]

Nevermind. I just did flutter upgrade and it looks like it has made it into stable.

[limyeanfen]

@chickenblood

Nevermind. I just did flutter upgrade and it looks like it has made it into stable.

May i know which version you upgraded ?

[iassal]

@limyeanfen I think it was fixed in Flutter 1.9.1+hotfix.6 as per the head commit here https://github.com/flutter/flutter/releases/tag/v1.9.1%2Bhotfix.6

[Deepanshu-Rohilla]

It is not fixed in the latest version

[violet-dev]

How to fix it?

[LongCatIsLooong]

The bug you're seeing is likely a different bug, since this one has long been hotfixed on the stable branch (unless you're still on a version older than 1.9.1). Could you file a new issue using this link?

[github-actions]

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.