当用户点击谷歌地图上的标记时，如何显示spinkit？(flutter_spinkit)

dependencies:
  flutter_spinkit: ^4.1.2

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

class MyMapScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My Map'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: () {
            showDialog(
              context: context,
              builder: (BuildContext context) {
                return AlertDialog(
                  content: SpinKitRotatingCircle(
                    color: Colors.blue,
                    size: 50.0,
                  ),
                );
              },
            );
          },
          child: Text('点击标记'),
        ),
      ),
    );
  }
}