I was trying to use the following flutter_sequence_animation: "^4.0.0-nullsafety"

however it fails - seems the update is not published.

Do you plan to publish ?

Virtually no arguments in the Flutter framework use abbreviations (like 'anim'). To keep this styling consistent, this pull request changes every instance of 'anim' to 'animatable' to preserve consistency in the Flutter framework.

Also, I've done some cleanup elsewhere (replaced vars and improved the example code for example).

It's just a styling choice, really, but I think it makes it more readable and consistent :)

Tried the example and updated the dependency for flutter_villains and everything worked ;) (at least for me). As suggested in #4, it is incompatible with flutter versions prior to 0.9.3-pre20 and should probably get a new version like 3.0.0 to avoid issues with people still using an older version of flutter.

Pull #21540 added the transform(double T) method and made evaluate use this method.

It's an easy fix, just change the IntervalAnimatable override to transform instead of evaluate, and remove the following line. Not sure how this will affect backward-compatibility though.

There are a ton of use-cases for having a looping animation.

My suggestion for the API would be to add a LoopMode to addAnimatable e.g. LoopMode.dontRepeat, LoopMode.pingPong, LoopMode.restart

Do you think this could be achieved with a reasonable amount of effort? @Norbert515

An offset or delay parameter for addAnimatable would be really useful. i.e. if you'd want to delay an animation by a certain duration then providing a delay Duration would remove the need for adding a duration to the from and to values.

Edit: I also think it would be useful if the SequenceAnimationBuilder had a "global" delay that affected all animatables

I always used flutter sequence on init and now I am trying to do it with gesturedetector, but i spend hours trying to figure out why it doesnt work. Could you kindly help? I want the height of the container to grow

import 'package:flutter/material.dart';
import 'package:flutter_sequence_animation/flutter_sequence_animation.dart';

// import 'package:speech_bubble/speech_bubble.dart';

class MyProcedureItem extends StatefulWidget {
  final String procedure, pics, description;
  final int index;
  MyProcedureItem(
      {Key key, this.procedure, this.pics, this.description, this.index})
      : super(key: key);
  @override
  _MyProcedureItemState createState() => _MyProcedureItemState();
}

class _MyProcedureItemState extends State<MyProcedureItem>
    with SingleTickerProviderStateMixin {
  ////////////////////////////////////////
  // Animation code
  AnimationController controller;
  SequenceAnimation sequenceAnimation;
  void initAnimation() {
    controller = AnimationController(vsync: this);
    SequenceAnimationBuilder sab = SequenceAnimationBuilder();

    sab.addAnimatable(
      animatable: Tween<double>(begin: 0.0, end: 300.0),
      from: Duration(milliseconds: 0),
      to: Duration(milliseconds: 5000),
      curve: Curves.easeInOutCirc,
      tag: 'question-height',
    );

    sequenceAnimation = sab.animate(controller);
  }

  @override
  void initState() {
    super.initState();
    initAnimation();
    // _playAnimation();
  }

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

  Future<Null> _playAnimation() async {
    try {
      await controller.forward().orCancel;
      // await controller.reverse().orCancel;
    } on TickerCanceled {
      // the animation got canceled, probably because we were disposed
    }
  }

  @override
  Widget build(BuildContext context) {
    double screenWidth = MediaQuery.of(context).size.width;
    double margin = 20;
    double wholeSize = screenWidth - margin * 2;
    
    
    Widget questions = Container(
      width: wholeSize,
      height:
          sequenceAnimation['question-height'].value ,
      color: Colors.blue,
      margin: EdgeInsets.fromLTRB(0, 0, 0, 20),
    );
    Widget detail = Container(width: 200, height: 200, color: Colors.green);
    return GestureDetector(
        onTap: () {
          _playAnimation();
        },
        child: AnimatedBuilder(
            animation: controller,
            builder: (context, child) => Padding(
                padding: EdgeInsets.fromLTRB(20, 0, 20, 0),
                child: Column(children: <Widget>[
                  detail,
                  questions,
                ])))); 
  }
}

class Procedure extends StatefulWidget {
  @override
  _ProcedureState createState() => _ProcedureState();
}

class _ProcedureState extends State<Procedure> {

  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.grey[100],
      body: Container(
          // A top margin of 56.0. A left and right margin of 8.0. And a bottom margin of 0.0.
          margin: const EdgeInsets.fromLTRB(0, 10, 0, 10),
          child: new Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              mainAxisSize: MainAxisSize.max,
              mainAxisAlignment: MainAxisAlignment.start,
              // A column widget can have several widgets that are placed in a top down fashion
              children: [
                MyProcedureItem(procedure: "blah", description: "foo", index: 0, pics: ""),
              ]))
    );
  }
}

Hi, thank you very much for your work on this package. It's been my favorite animation add-on since its very first version years ago!

I've been thinking about a little revamp of the API in order to make it more sound at compile-time. It leverages tags/keys that are generics on the animation type they want to represent, so that it's guaranteed that you can only add animatables (for example tweens) of the given tag type and also extract values of the animatable while using them for the animation at a later time.

I'll submit this as a draft PR because, if you like the approach, some work needs to be done in order to handle backward compatibility and reword the docs.