Controlling animation from other widget - flutter

Question

I'm trying to control an animation on a widget (widget 2 in the pic) using gestures captured from another widget (widget 1 in the pic) and I'm having trouble finding the right way to do that.
The approach I currently think about is having the AnimationController in a common parent. widget 1 would, via callbacks, update the value of this controller in the parent. widget 2 would receive that controller a a parameter and therefore the animation in widget 2 would correspond to the values provided by the gestures in widget 1
Is that the right way to do it ? If not, what would be a better approach ?
Edit: After trying this method, I notice that an exception get thrown
Another exception was thrown: AnimationController.dispose() called more than once.
I suspect the AnimationController object to be reconstructed on rebuild causing the error. Any idea on how to do it to avoid that ?
Thanks ! :)

Answer 1

Here is a full sample of what I think you're trying to achieve, using AnimatedWidget. Might not be the most efficient way to do it, but it works.
import 'package:flutter/material.dart';
void main() => runApp(App());
class App extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: Text("Test")),
body: SafeArea(child: Parent()),
),
);
}
}
class Parent extends StatefulWidget {
#override
_ParentState createState() => _ParentState();
}
class _ParentState extends State<Parent> with SingleTickerProviderStateMixin {
AnimationController _animationController;
Animation<double> _animation;
#override
void initState() {
super.initState();
_animationController = AnimationController(vsync: this);
_animation =
Tween<double>(begin: 0, end: 100).animate(_animationController);
}
#override
void dispose() {
super.dispose();
_animationController.dispose();
}
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
Expanded(child: Widget1(animation: _animation)),
Widget2(onSliderChanged: (value) {
_animationController.value = value / 100;
}),
],
);
}
}
class Widget1 extends AnimatedWidget {
Widget1({Key key, #required Animation<double> animation})
: super(key: key, listenable: animation);
#override
Widget build(BuildContext context) {
Animation<double> animation = listenable;
return Opacity(
opacity: animation.value / 100,
child: Center(
child: Text(
"Hi",
style: TextStyle(fontWeight: FontWeight.bold, fontSize: 40.0),
),
),
);
}
}
class Widget2 extends StatefulWidget {
final ValueChanged<double> onSliderChanged;
const Widget2({Key key, this.onSliderChanged}) : super(key: key);
#override
State<StatefulWidget> createState() => _Widget2State();
}
class _Widget2State extends State<Widget2> {
double _value = 0;
#override
Widget build(BuildContext context) {
return Slider(
value: _value,
min: 0,
max: 100,
onChanged: (value) {
setState(() {
_value = value;
});
widget.onSliderChanged(value);
},
);
}
}