Flutter put AnimatedIcon instead of AppBar leading icon

Issue

in my application i’m trying to using AnimatedIcon instead of Appbar, leading icon, for changing controller of AnimatedIcon i’m using Provider package, but i get this error:

setState() or markNeedsBuild() called during build.

my AppBar:

AppBar(
  elevation: 8.0,
  titleSpacing: 0.0,
  automaticallyImplyLeading: true,
  leading: Consumer<AppBarAnimatedIconMode>(
      builder: (context, mode, child) => ValueListenableProvider.value(
          value: mode.iconMode,
          child: Consumer<bool>(
              builder: (context, value, child) => AppBarAnimatedIcon(
                    animate: value,
                  )))),

AppBarAnimatedIcon class:

class AppBarAnimatedIcon extends StatefulWidget {
  final bool animate;

  const AppBarAnimatedIcon({@required this.animate});

  @override
  State<StatefulWidget> createState() => _AppBarAnimatedIcon();
}

class _AppBarAnimatedIcon extends State<AppBarAnimatedIcon> with TickerProviderStateMixin {
  AnimationController _animationController;
  bool get _animate => widget.animate;
  @override
  void initState() {
    super.initState();
    _animationController = AnimationController(vsync: this, duration: const Duration(milliseconds: 500));
    if(_animate){
      _animationController.forward();
    }else{
      _animationController.reverse();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: AnimatedIcon(
        icon: AnimatedIcons.menu_close,
        progress: _animationController,
      ),
    );
  }
}

ValueNotifier class to change AnimatedIcon animation controller:

class AppBarAnimatedIconMode {
  final ValueNotifier<bool> iconMode = ValueNotifier<bool>(false);

  // ignore: use_setters_to_change_properties
  void changeIconMode() {
    iconMode.value = !iconMode.value;
  }
}

full error message:

This _DefaultInheritedProviderScope<bool> widget cannot be marked as needing to build because the framework is already in the process of building widgets.  A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
The widget on which setState() or markNeedsBuild() was called was: _DefaultInheritedProviderScope<bool>
  value: false
The widget which was currently being built when the offending call was made was: BuildDefaultAppBar
  dirty
  dependencies: [_EffectiveTickerMode]
  state: _BuildDefaultAppBar#a5ab5(tickers: tracking 1 ticker)
When the exception was thrown, this was the stack: 
#0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:4167:11)
#1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:4182:6)
#2      _InheritedProviderScopeMixin.markNeedsNotifyDependents (package:provider/src/inherited_provider.dart:269:5)
#3      _DeferredDelegateState.setState (package:provider/src/deferred_inherited_provider.dart:139:17)
#4      ValueListenableProvider._startListening.<anonymous closure>.<anonymous closure> (package:provider/src/value_listenable_provider.dart:74:38)
...
The ValueNotifier<bool> sending notification was: ValueNotifier<bool>#7aa18(true)  

Solution

I created a new project and I tried your code. Firstly if you use Provider, you should use ChangeNotifier with your control classes. Also you should use ChangeNotifierProvider with your main class. These are my codes which is working well.

main.dart

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: ChangeNotifierProvider(
        create: (context) => AppBarAnimatedIconMode(), // This is condition class.
        child: Home(),
      ),
    );
  }
}

AppBarAnimatedIconMode.dart

class AppBarAnimatedIconMode with ChangeNotifier {
  final ValueNotifier<bool> iconMode = ValueNotifier<bool>(false);

  // ignore: use_setters_to_change_properties
  void changeIconMode() {
    iconMode.value = !iconMode.value;
    notifyListeners(); // For change the state of icon value.
  }
}

AppBarAnimatedIcon.dart

class AppBarAnimatedIcon extends StatefulWidget {
  final bool animate;

  const AppBarAnimatedIcon({@required this.animate});

  @override
  State<StatefulWidget> createState() => _AppBarAnimatedIcon();
}

class _AppBarAnimatedIcon extends State<AppBarAnimatedIcon> with SingleTickerProviderStateMixin {// You should use SingleTickerProviderStateMixin //
  AnimationController _animationController;

  bool get _animate => widget.animate;

  @override
  void initState() {
    super.initState();
    _animationController = AnimationController(vsync: this, duration: const Duration(milliseconds: 500));
  }

  @override
  void dispose() { // Also dispose your animation when you dispose the class.
    _animationController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    if (_animate) { // You should check your conditions in your build() for animate
      _animationController.forward();
    } else {
      _animationController.reverse();
    }
    return Center(
      child: AnimatedIcon(
        icon: AnimatedIcons.menu_close,
        progress: _animationController,
      ),
    );
  }
}

So you can control you animation like this function:

RaisedButton(
      child: Text('Change'),
      onPressed: () {
        var provider = Provider.of<AppBarAnimatedIconMode>(context, listen: false);
        provider.changeIconMode();
      },

Also on your AppBar, you can use this code. Yours is complicated.

AppBar(
    title: Text('Deneme'),
    leading: Consumer<AppBarAnimatedIconMode>(
      builder: (context, mode, child) => AppBarAnimatedIcon(
        animate: mode.iconMode,
      ),
    ),
  ),

And for AppBarAnimatedIconMode.dart

class AppBarAnimatedIconMode with ChangeNotifier {
  bool iconMode = false;

  void changeIconMode() {
    iconMode = !iconMode;
    notifyListeners();
  }
}

Answered By – FurkanKURT

Answer Checked By – Timothy Miller (FlutterFixes Admin)

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