Invalid reference to 'this' expression. Animation Controller-CodePudding

I have this error when I try to load Animation Controller. This problem shows when I changed my SDK 2.15.0 to 2.7.0. Red line in "vsync: this" This is my code:

main.dart

class SplashScreenState extends State<SplashScreen>
    with SingleTickerProviderStateMixin {
  final AnimationController _animationController = AnimationController(
      vsync: this, duration: const Duration(milliseconds: 500));
  String _connectionStatus = 'unKnown';
  final Connectivity _connectivity = Connectivity();
  StreamSubscription<ConnectivityResult> connectivitySubscription;
  Future<void> _initPackageInfo() async {
    final info = await PackageInfo.fromPlatform();
    setState(() {
      packageInfo = info;
    });
  }

SplashScreen.dart

AnimationController animationController = AnimationController(
      vsync: this, duration: const Duration(milliseconds: 5));

the error is vsync: this. Red line.

CodePudding user response：

Just insert a late before assigning a final variable like this:

late final AnimationController _animationController = AnimationController(
      vsync: this, duration: const Duration(milliseconds: 500));

If you need explanation, comment below.