Flutter AnimationController

State要加上with SingleTickerProviderStateMixin，
Tween(begin: 0.0, end: 90.0)是在Duration(milliseconds: 100)一百毫秒里返回0.0-90.0的double值，需要调用的地方用lineAnimation.value取值，..addListener，这个前面加..的语法是指用Tween(begin: 0.0, end: 90.0).animate(lineController)的返回值来调用addListener

class _FollowListState extends State<FollowList>
    with SingleTickerProviderStateMixin {

  AnimationController lineController;
  Animation<double> lineAnimation;

  @override
  initState() {
    super.initState();

    lineController = AnimationController(
        vsync: this, duration: const Duration(milliseconds: 100));
    lineAnimation =
        Tween(begin: 0.0, end: 90.0)
            .animate(lineController)
              ..addListener(() {
                setState(() {});
              });
  }

  @override
  dispose() {
    // 释放
    lineController.dispose();
    super.dispose();
  }

调用：

Container(
    margin: EdgeInsets.only(left: lineAnimation.value),
    width: 90,
    height: 3,
    decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(1.5),
        color: mainColor,
    ),
),

执行动画:

lineController.forward();

反向执行:

lineController.reverse();

加入addStatusListener可以监听动画执行状态，可以在回调里进行动画循环:

lineAnimation = Tween(begin: 0.0, end: 90.0).animate(lineController)
      ..addListener(() {
        setState(() {});
      })
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed) {
          lineController.reverse();
        } else if (status == AnimationStatus.dismissed) {
          lineController.forward();
        }
      });