答案Scaffold.of(context). showsnackbar(…)在大多数情况下都不起作用。

我建议最佳的方法是在类中声明一个Scaffold state键，并将其分配给Scaffold，如下所示:

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

然后

Scaffold(
  key: _scaffoldKey,
  ...
)

当你想要显示零食栏时，这样做:

_scaffoldKey.currentState.showSnackBar(SnackBar(
  content: Text("This works!"),
));

fluttertoast: ^ 3.1.3

import 'package:fluttertoast/fluttertoast.dart';

Fluttertoast.showToast(
        msg: "This is Center Short Toast",
        toastLength: Toast.LENGTH_SHORT,
        gravity: ToastGravity.CENTER,
        timeInSecForIos: 1,
        backgroundColor: Colors.red,
        textColor: Colors.white,
        fontSize: 16.0
    );

更新:Scaffold.of(上下文)。showSnackBar在Flutter 2.0.0中已弃用(稳定)

你可以使用ScaffoldMessenger.of(context)访问父类ScaffoldMessengerState。

然后做一些类似的事情

ScaffoldMessenger.of(context).showSnackBar(SnackBar(
      content: Text("Sending Message"),
    ));

零食条是材料设计的官方“吐司”。看到间小吃店。

下面是一个完整的例子:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: Home(),
    );
  }
}

class Home extends StatelessWidget {
  const Home({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Snack bar'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: () => _showToast(context),
          child: const Text('Show toast'),
        ),
      ),
    );
  }

  void _showToast(BuildContext context) {
    final scaffold = ScaffoldMessenger.of(context);
    scaffold.showSnackBar(
      SnackBar(
        content: const Text('Added to favorite'),
        action: SnackBarAction(label: 'UNDO', onPressed: scaffold.hideCurrentSnackBar),
      ),
    );
  }
}

你可以直接使用小吃店的元素

 ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text("Successfully!"),
        behavior: SnackBarBehavior.floating,
        margin: EdgeInsets.all(20),
          shape: StadiumBorder(),
        action: SnackBarAction(
          label: 'Dismiss',
          disabledTextColor: Colors.white,
          textColor: Colors.blue,
          onPressed: () {
            //Do whatever you want
          },
        ),
      ),
    );

您可以使用飘动吐司包装。为此，将其添加到pubspec中。Yaml文件如下:

dependencies:
  fluttertoast: ^8.0.8

然后在需要吐司的.dart文件中导入这个包并编写代码。

例如，参考以下代码:

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

class ToastExample extends StatefulWidget {
    @override
    _ToastExampleState createState() {
      return _ToastExampleState();
    }
  }

  class _ToastExampleState extends State {
    void showToast() {
      Fluttertoast.showToast(
          msg: 'This is flutterToast example', // Message
          toastLength: Toast.LENGTH_SHORT,    // toast length
          gravity: ToastGravity.CENTER,      // position
          timeInSecForIos: 1,               // duaration
          backgroundColor: Colors.red,     // background color
          textColor: Colors.white         // text color
      );
    }

    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Toast Tutorial',
        home: Scaffold(
            appBar: AppBar(
              title: Text('Toast Tutorial'),
            ),
            body: Padding(
              padding: EdgeInsets.all(15.0),
              child: Center(
                child: RaisedButton(
                  child: Text('Show Toast'),
                  onPressed: showToast,
                ),
              ),
            )
        ),
      );
    }
  }

  void main() => runApp(ToastExample());

用https://pub.dev/packages/toast做吐司。这个库非常容易使用，适用于iOS和Android。

显示Toast的语法:

Toast.show("Toast plugin app", duration: Toast.LENGTH_SHORT, gravity:  Toast.BOTTOM);