AnimationController The named parameter 'vsync' isn't defined

Question

AnimationController stopped working because somehow vsync is not a named parameter anymore.

This line of code stopped working.

controller = AnimationController(duration: Duration(seconds: 3), vsync: this);

It now shows an error saying:

The named parameter 'vsync' isn't defined.
Try correcting the name to an existing named parameter's name, or defining a named parameter with the name 'vsync'.dartundefined_named_parameter

I use this exact same code in two different apps, in one of them I just removed the fading text animation as a hot fix, but on the other app I need a real fix. Has anyone seen this problem recently?

Note:

-This exact same code has been working for months and stopped working after an update.

-The surrounding class does have: with TickerProviderStateMixin

class FadingText extends StatefulWidget {
  final String text;
  final int seconds;
  final TextStyle style;

  FadingText({this.text, this.seconds, this.style});

  @override
  _FadingTextState createState() => _FadingTextState();
}

class _FadingTextState extends State<FadingText> with TickerProviderStateMixin {
  AnimationController controller;
  Animation animation;

  @override
  Widget build(BuildContext context) {
    return Container(
      child: FadeTransition(
        opacity: animation,
        child: Text(widget.text, style: widget.style,),
      ),
    );
  }

  @override
  void initState() {
    super.initState();

    controller = AnimationController(duration: Duration(seconds: widget.seconds), vsync: this);
    animation = Tween(begin: 0.5, end: 1.0).animate(controller);

    animation.addStatusListener((status) {
      if (status == AnimationStatus.completed) { controller.reverse(); }
      else if (status == AnimationStatus.dismissed) { controller.forward(); }
    });

    controller.forward();
  }


  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

}

Flutter Doctor


[✓] Flutter (Channel master, 1.21.0-6.0.pre.140, on Mac OS X 10.15.5 19F101, locale en-MX)
    • Flutter version 1.21.0-6.0.pre.140 at /Users/luisharo/Developer/flutter
    • Framework revision 7884420a0a (25 hours ago), 2020-07-31 20:20:00 +0200
    • Engine revision 280bbfc763
    • Dart version 2.10.0 (build 2.10.0-2.0.dev bd528bfbd6)

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/luisharo/Library/Android/sdk
    • Platform android-29, build-tools 29.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
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• No issues found!

Solution 1

In your pubspec.yml

change this to:

environment:
  sdk: ">=2.8.0 <3.0.0"

and flutter pub get

in Android Studio invalidate the cache and restart, you should be good to go.

Credit : https://github.com/flutter/flutter/issues/62752#issuecomment-667744745

Solution 2

What happened is that @required syntax was migrated during the rollout of null-safety to now just be required. This is valid new-Dart, but if you upgrade with your editor open, it will have stale build rules. Simply run flutter clean and restart your IDE, and that should do it.

Hopefully no need to restart your computer, change internet providers, etc.

Solution 3

A few things (unfortunately not pinpointed) that help me with issues like this:

**edit: I would recommend doing these in order, hopefully the issue will be solved before you reach the end of the list.

• run flutter upgrade
• run flutter pub get
• run flutter clean
• restart IDE
• change flutter channel
• and in this case, change minimum SDK version from 2.7.0 to 2.8.0.

There are, of course, caveats to a few of these tactics. More experienced developers would surely have more details to offer, but I haven't encountered issues with this approach.

Solution 4

Had the same issue after upgrading flutter. Restarting the IDE fixed the problem.

Solution 5

I ran into the same issue when I upgraded to Flutter 1.22.

I am using VS Code.

Simply run: Flutter Clean in the Terminal and restart your IDE. That should fix the problem!

View more solutions

Comments

[Mariano Zorrilla]

Could you post your class constructor? And where you tried to implement your Controller?

[Chamanhm]

Hi Mariano, I posted an edit with the whole class.

[Mariano Zorrilla]

could you also post your "flutter doctor -v"? Is the same issue happening using the single ticker provider?

[Rémi Rousselet]

Do you have another class with the same name maybe?

[Chamanhm]

I added the results of flutter doctor -v... also checked that the class is not duplicated.

[Chamanhm]

Same error if trying with SingleTickerProviderStateMixin

[Quentin Aoustin]

I am currently running into the same issue. This is probably a bug introduce since the last update... Try to open an issue on the flutter GitHub page it should be fixed quickly if this issue is as spread as I think. By checking here : github.com/flutter/flutter/commit/… You can see the modifications made 4 days ago.

[sultanmyrza]

to "invalidate the cache and restart" in android studio click (File -> Invalidate Caches/Restart)

[Quyen Anh Nguyen]

As for me I need one more step is reload IDE :D Thanks, it works like a charm.

[Elia Weiss]

I first change sdk: ">=2.8.0 <3.0.0" in pubspec.yml and then a restart, not sure which one solved the issue.

[Admin]

Only doing the first four steps solved the issue.

[Nouman Hanif]

for VSCode, do 'Restart Analysis Server', ctrl+shift+p to bring up the command palette and type 'analysis' to search for it. This will save you from restarting the IDE

[Hashem Aboonajmi]

Editor Restart fixed it

[Jan]

This solved the issue for me, thank