Flutter 设置开始动画值

Question

我想传入一个值来将起始动画值设置为 1.0 而不是从 0 开始，但我不知道这是如何实现的。

class AnimatedIconButton extends StatefulWidget {
  AnimatedIconButton(this.img, this.start);
  final String img;
  final double start;
  @override
  _AnimatedIconButtonState createState() => _AnimatedIconButtonState();
}

class _AnimatedIconButtonState extends State<AnimatedIconButton>
    with TickerProviderStateMixin {
  AnimationController _controller;
  Animation _animation;

  void animateButton() {
    if (_animation.value == 0)
      _controller.forward();
    else
      _controller.reverse();
  }

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: Duration(milliseconds: 300),
      vsync: this,
    );
    _animation =
        CurvedAnimation(parent: _controller, curve: Curves.easeOutQuad);
    _controller.addListener(() {
      setState(() {});
    });
    _animation.value = widget.start;// does not work
  }

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

  @override
  Widget build(BuildContext context) {
    return MaterialButton(
      splashColor: Colors.white,
      highlightColor: Colors.white,
      child: Image.asset("images/${widget.img}.png",
          width: 33 + (16 * _animation.value)),
      onPressed: () {
        animateButton();
      },
    );
  }
}

Answer 1

您可以使用：

_controller.forward(from: 0.0);

或者

_controller.reverse(from: 1.0);

并设置您需要的值

或者为了设置初始值，您可以使用

_controller.value = widget.start;