Animate a color periodically in flutter - flutter

Question

I have a container widget that I try to animate from Colors.blue to Colors.blueGrey and back periodically every 2 seconds.
How can I most easily tackle this in Flutter?

Answer 1

You can use an infinite while loop, don't think this is the best way of doing this, but it gets the job done.
I have a Color Changing class
class ColorChanger extends StatefulWidget {
#override
_ColorChangerState createState() => _ColorChangerState();
}
class _ColorChangerState extends State<ColorChanger>
with SingleTickerProviderStateMixin {
AnimationController _animationController;
Animation _colorTween;
#override
void initState() {
_animationController = AnimationController(
vsync: this, duration: Duration(milliseconds: 1999));
_colorTween = ColorTween(begin: Colors.blue, end: Colors.blueGrey)
.animate(_animationController);
changeColors();
super.initState();
}
Future changeColors() async {
while (true) {
await new Future.delayed(const Duration(seconds: 2), () {
if (_animationController.status == AnimationStatus.completed) {
_animationController.reverse();
} else {
_animationController.forward();
}
});
}
}
#override
Widget build(BuildContext context) {
return AnimatedBuilder(
animation: _colorTween,
builder: (context, child) => Container(
color: _colorTween.value,
),
);
}
}
This is a rough example, but should lead you in the right direction.
Please see ColorTween Class

Answer 2

I would suggest using the AnimatedContainer. This widget allows you to build it with a particular atribute like color and when you rebuild it with a different value it performs linear interpolation between those values.
#override
Widget build(BuildContext context) {
return AnimatedContainer(
width: 100,
height: 100,
duration: _animationDuration,
color: _color,
);
}
Then you just have to rebuild the widget with a different color:
void _changeColor() {
final newColor = _color == Colors.blue ? Colors.blueGrey : Colors.blue;
setState(() {
_color = newColor;
});
}
The make it periodically I would use a timer class:
_timer = Timer.periodic(_animationDuration, (timer) => _changeColor());
The whole code:
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
class AnimationTest extends StatefulWidget {
#override
_AnimationTestState createState() => _AnimationTestState();
}
class _AnimationTestState extends State<AnimationTest> {
final _animationDuration = Duration(seconds: 2);
Timer _timer;
Color _color;
#override
void initState() {
super.initState();
_timer = Timer.periodic(_animationDuration, (timer) => _changeColor());
_color = Colors.blue;
}
void _changeColor() {
final newColor = _color == Colors.blue ? Colors.blueGrey : Colors.blue;
setState(() {
_color = newColor;
});
}
#override
Widget build(BuildContext context) {
return AnimatedContainer(
width: 100,
height: 100,
duration: _animationDuration,
color: _color,
);
}
#override
void dispose() {
super.dispose();
_timer.cancel();
}
}