dependencies:
fluttertoast: ^3.1.3

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

void main() {
runApp(MaterialApp(
title: "DialogWidget",
home: MyApp(),
));
}

class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}

class _MyAppState extends State {

_toast(){
Fluttertoast.showToast(
msg: "登录成功",
toastLength: Toast.LENGTH_LONG,
gravity: ToastGravity.BOTTOM, // 消息框弹出的位置
timeInSecForIos: 1, // 消息框持续的时间（目前的版本只有ios有效）
backgroundColor: Colors.red,
textColor: Colors.white,
fontSize: 16.0
);
}

@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: RaisedButton(
child: Text("toast"),
onPressed: _toast,
),
)
);
}
}