Le Tutoriel de Flutter SnackBar

const SnackBar(
    {Key key,
    @required Widget content,
    Color backgroundColor,
    double elevation,
    EdgeInsetsGeometry margin,
    EdgeInsetsGeometry padding,
    double width,
    ShapeBorder shape,
    SnackBarBehavior behavior,
    SnackBarAction action,
    Duration duration: _snackBarDisplayDuration,
    Animation<double> animation,
    VoidCallback onVisible}
)

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'o7planning.org',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter SnackBar Example'),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {},
      ),
      body: Center(
          child: Builder(
              builder: (BuildContext ctxOfScaffold)  {
                return ElevatedButton(
                    child: Text('Show SnackBar'),
                    onPressed: () {
                      this._showSnackBarMsgDeleted(ctxOfScaffold);
                    }
                );
              }
          )
      )
    );
  }

  void _showSnackBarMsgDeleted(BuildContext ctxOfScaffold) {
    // Create a SnackBar.
    final snackBar = SnackBar(
      content: Text('Message is deleted!'),
      action: SnackBarAction(
        label: 'UNDO',
        onPressed: () {
          this._showSnackBarMsgRestored(ctxOfScaffold);
        },
      ),
    );
    // Find the Scaffold in the widget tree
    // and use it to show a SnackBar.
    Scaffold.of(ctxOfScaffold).showSnackBar(snackBar);
  }

  void _showSnackBarMsgRestored(BuildContext ctxOfScaffold) {
    // Create a SnackBar.
    final snackBar = SnackBar(
      content: Text('Message is restored!')
    );
    // Find the Scaffold in the widget tree
    // and use it to show a SnackBar.
    Scaffold.of(ctxOfScaffold).showSnackBar(snackBar);
  }
}

@required Widget content

Color backgroundColor

double elevation

final snackBar = SnackBar(
  content: Text('Message is deleted!'),
  elevation: 15,
  behavior: SnackBarBehavior.floating,
  action: SnackBarAction(
    label: 'UNDO',
    onPressed: ()  {
    },
  ),
)

EdgeInsetsGeometry margin

EdgeInsetsGeometry padding

double width

ShapeBorder shape

SnackBarBehavior behavior

// Enum values:
SnackBarBehavior.fixed
SnackBarBehavior.floating

SnackBarAction action

Duration duration: _snackBarDisplayDuration

Animation<double> animation

SnackBar withAnimation (
  Animation<double> newAnimation,
  {Key fallbackKey}
)

VoidCallback onVisible