Flutter: how to play animation with Provider?

Question

I use Provider to manage state in my Flutter demo.

I want to animate my widget but it seems that AnimateController needs a sync parameter that comes from the state of a stateful widget.

As far as I know, Provider is not recommended to use with a stateful widget.

Can I manage the AnimationController with Provider?

Or must use both Provider and stateful widget?

Answer 1

If you want to create AnimationController in the StatelessWidget you must pass TickerProviderStateMixin in the Constructor of your StatelessWidget, look at my sample code :

import 'package:flutter/material.dart';

main() {
  runApp(TestyApp());
}

class TestyApp extends StatefulWidget {
  @override
  _TestyAppState createState() => _TestyAppState();
}

class _TestyAppState extends State<TestyApp> with TickerProviderStateMixin {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: TestAnimationInStatelessWidget(
        tickerProviderStateMixin: this,
      ),
    );
  }
}

class TestAnimationInStatelessWidget extends StatelessWidget {
  final TickerProviderStateMixin tickerProviderStateMixin;

  const TestAnimationInStatelessWidget(
      {Key key, @required this.tickerProviderStateMixin})
      : assert(tickerProviderStateMixin != null),
        super(key: key);

  @override
  Widget build(BuildContext context) {

    var _animationController = AnimationController(
        vsync: tickerProviderStateMixin, duration: Duration(seconds: 1));

    var _animation = Tween<double>(begin: 0, end: 2).animate(CurvedAnimation(
        parent: _animationController, curve: Curves.easeInOut));

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            RotationTransition(
              turns: _animation,
              child: Container(
                width: 200,
                height: 200,
                decoration: BoxDecoration(
                  color: Colors.blueGrey,
                  borderRadius: BorderRadius.all(Radius.circular(15)),
                ),
              ),
            ),
            SizedBox(
              height: 30,
            ),
            RaisedButton(
              onPressed: () {
                _animationController.reset();
                _animationController.forward();
              },
              child: Text("Start Animation"),
            )
          ],
        ),
      ),
    );
  }
}

Answer 2

Can I manage the AnimationController with Provider?

Or must use both Provider and stateful widget?

I don't know if this is the best way to do it, but here is how I do this :

I use didUpdateWidget in a Stateful widget. I pass the value from the provider to the parent and trigger the animation in the didUpdateWidget method defined in the child. didUpdateWidget being triggered itself when I notify listeners from a change in the Provider.

class MyWidget extends StatefulWidget {
  final String valueFromProvider;

  MyWidget({this.valueFromProvider});

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

class _MyWidgetState extends State<MyWidget> with TickerProviderStateMixin {
  @override
  void didUpdateWidget(MyWidget oldWidget) {
    // TODO: implement didUpdateWidget
    super.didUpdateWidget(oldWidget);

    if (oldWidget.valueFromProvider == "whatever you want" &&
        widget.valueFromProvider == "what you want that changed") {
      // trigger animations methods here
    }
  }

  // here all the animations methods,dispose method, etc. 

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}