return AnimatedBuilder(
      animation: _controller.view,
      child: child,
      builder: (BuildContext context, Widget? child) {
        return Align(
          heightFactor: _heightFactor.value,
          //fix 从布局之上的位置开始展开
          alignment: Alignment.topCenter,
          child: Container(
            //会撑满宽度后，让内容对其
            alignment: Alignment.topLeft,
            padding: EdgeInsets.only(top: 8),
            child: child,
          ),
        );
      },
    );

这里的_controller.view就是指动画绑定的view吧
_controller = AnimationController(duration: Duration(milliseconds: 200), vsync: this);
那么这里vsync: this， vsync这个参数设置就是绑定的view吗