flutter - 如何在 flutter 中使用 AnimatedPositioned 的 AnimatedSize 子项？

Question

我想在 AnimatedPositioned 的 child 中使用 AnimatedSize，但我得到了异常(exception)。
这是我的代码:

AnimatedPositioned(
  duration: Duration(seconds: 2),
  curve: Curves.fastLinearToSlowEaseIn,
  top: isProfileSelected ? 100 : 0,
  child: Transform.translate(
    offset:
     Offset(isProfileSelected ? MediaQuery.of(context).size.width / 2 - 53 :MediaQuery.of(context).size.width / 2 - 38, 90 / 2),
    child: AnimatedSize(
      curve: Curves.fastOutSlowIn,
      child: isProfileSelected ? SizedBox(
        width: 106.0,
        child: circleAvatar(106, 106),
      ) : SizedBox(
        width: 76.0,
        child: circleAvatar(76, 76),
      ),
    ),
  ),
),

Answer 1

将此添加到您的类(class)状态

class _MyWidgetState extends State<_MyWidget> with SingleTickerProviderStateMixin {
    .............
  AnimatedPositioned(
    duration: Duration(seconds: 2),
    curve: Curves.fastLinearToSlowEaseIn,
    top: isProfileSelected ? 100 : 0,
    child: Transform.translate(
    offset:
     Offset(isProfileSelected ? MediaQuery.of(context).size.width / 2 - 53 :MediaQuery.of(context).size.width / 2 - 38, 90 / 2),
    child: AnimatedSize(
      vsync: this, //This must be required
      duration: Duration(milliseconds: 200), //Duration is also required
      curve: Curves.fastOutSlowIn,
      child: isProfileSelected ? SizedBox(
        width: 106.0,
        child: circleAvatar(106, 106),
      ) : SizedBox(
        width: 76.0,
        child: circleAvatar(76, 76),
      ),
    ),
  ),
),
......................

}