Multiple controllers with AnimatedBuilder in flutter

Question

I was searching for a way to combine repetitive and not repetitive animations in Flutter. For example, start opening animation (not repetitive) and then show some repetitive animation, like bouncing animation. Currently, I've used 2 animated controllers and 2 animatedBuilders above one widget. Here is my sample code:

   @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
        animation: _outerAnimationController, //starting animation, not repetitive
        builder: (context, _) {
          return AnimatedBuilder( 
              animation: _innerCurvedAnimation, //repetitive animation, bouncing
              builder: (context, _) {
                return CustomPaint(
                  size: Size(MediaQuery.of(context).size.width,
                      MediaQuery.of(context).size.height),
                  painter: ShowCasePainter(
                    centerPosition: Offset(
                        MediaQuery.of(context).size.width / 2,
                        MediaQuery.of(context).size.height / 2),
                    innerCircleRadius: widget.innerCircleRadius +
                        (_innerCurvedAnimation.value * PaddingSmall), //repetitive animation value, bouncing
                    outerCircleRadius: _outerAnimationTween.value, //starting animation value, not repetitive
                  ),
                );
              });
        });
  }

Is it a good practice on using multiple controllers in this way? How to influence animatedBuilder from two controllers representing different animations?

Thanks for your help!

Please, post your comment as answer, I'll check it as correct! — Atamyrat Babayev
– Atamyrat Babayev, Commented Sep 14, 2021 at 10:34
feel free to write a self answer if Listenable.merge worked for you — pskink
– pskink, Commented Sep 14, 2021 at 10:41

pskink · Accepted Answer · 2021-09-14 15:21:34Z

21

With the help of @pskink I've finally found solution. No need in use multiple AnimatedBuilders here, Listenable.merge with multiple AnimationControllers will be enought. Merging possible because AnimationControllers extends from Listenable class. Here is correct code:

@override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
        animation: Listenable.merge(
            [_innerAnimationController, _outerAnimationController]),
        builder: (context, _) {
          return CustomPaint(
            size: Size(MediaQuery.of(context).size.width,
                MediaQuery.of(context).size.height),
            painter: ShowCasePainter(
              centerPosition: Offset(MediaQuery.of(context).size.width / 2,
                  MediaQuery.of(context).size.height / 2),
              innerCircleRadius: widget.innerCircleRadius +
                  (_innerCurvedAnimation.value * PaddingSmall),
              outerCircleRadius: _outerAnimationTween.value,
            ),
          );
        });
  }

This solution will be ok with any widget, but with CustomPainter there is a better solution. In case of Custom painter, animationControllers can be passed throught constructor into CustomPainter and inside of this class should be merged. Parent build method:

 @override
  Widget build(BuildContext context) {
    return CustomPaint(
      willChange: true,
      size: Size(MediaQuery.of(context).size.width,
          MediaQuery.of(context).size.height),
      painter: ShowCasePainter(
        centerPosition: Offset(MediaQuery.of(context).size.width / 2,
            MediaQuery.of(context).size.height / 2),
        innerCircleRadius: widget.innerCircleRadius,
        outerCircleRadius: widget.outerCircleRadius,
        innerAnimationController: _innerAnimationController,
        outerAnimationController: _outerAnimationController,
      ),
    );
  }

As you see, I passed only immutable values, instead of using values from controllers/animations. And here is CustomPainter constructor:

class ShowCasePainter extends CustomPainter {
  final Offset centerPosition;
  final double innerCircleRadius;
  final double outerCircleRadius;
  final Color backgroundColor;
  final Color ringColor;
  final Animation<double> innerAnimationController;
  final Animation<double> outerAnimationController;
  Animation<double> _innerCurvedAnimation;
  Animation<double> _outerAnimationTween;
  Animation<Color> _backgroudColorTween;
  ShowCasePainter(
      {this.innerAnimationController,
      this.outerAnimationController,
      this.centerPosition,
      this.innerCircleRadius = 32.0,
      this.outerCircleRadius = 128.0,
      this.backgroundColor,
      this.ringColor})
      : super(
            repaint: Listenable.merge(
                [innerAnimationController, outerAnimationController])) {
    _innerCurvedAnimation =
        CurvedAnimation(parent: innerAnimationController, curve: Curves.easeIn);

    _outerAnimationTween =
        Tween(begin: innerCircleRadius, end: outerCircleRadius)
            .animate(outerAnimationController);

    _backgroudColorTween = ColorTween(
            begin: Colors.transparent,
            end: backgroundColor ?? Colors.black.withOpacity(0.2))
        .animate(outerAnimationController);
  }

Now animations will work correct.

edited Sep 14, 2021 at 15:21

pskink

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answered Sep 14, 2021 at 11:15

Atamyrat Babayev

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3 Comments

pskink Over a year ago

btw you dont need AnimatedBuilder and creating a new ShowCasePainter for every animation frame - instead check CustomPainter constructor and its repaint optional parameter - that way you create just one ShowCasePainter that "repaints" itself when this Listenable triggers

Atamyrat Babayev Over a year ago

I thought that if you want to listen for updates there must be some king of observer. I understand what you mean. I need to check it out. Thanks!))

Atamyrat Babayev Over a year ago

Unfortunately, it doesn't work with AnimationControllers. So, I found your response: stackoverflow.com/a/58595116/10084055, which is not what I'm searching for. In addition, I found solution with setState, which is dirtier solution. Example is, add listener on merged listenables above custom painter class and call setstate on each controllers update.

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