如何在flutter中实现浮动Snackbar动画？

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

final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

Scaffold(
  key: _scaffoldKey,
  // ...
)

void showFloatingSnackbar(String message) {
  _scaffoldKey.currentState.showSnackBar(
    SnackBar(
      content: Text(message),
      behavior: SnackBarBehavior.floating,
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(10),
      ),
      margin: EdgeInsets.all(16),
      elevation: 6,
      duration: Duration(seconds: 2),
      animation: _createAnimation(),
    ),
  );
}

Animation<double> _createAnimation() {
  AnimationController controller = AnimationController(
    vsync: _scaffoldKey.currentState,
    duration: Duration(milliseconds: 500),
  );
  CurvedAnimation curve =
      CurvedAnimation(parent: controller, curve: Curves.easeOut);
  Animation<double> animation =
      Tween<double>(begin: 0, end: 1).animate(curve);
  controller.forward();
  return animation;
}

showFloatingSnackbar('This is a floating Snackbar');