dependencies:
    showcaseview: ^0.1.1

import 'package:showcaseview/showcaseview.dart';

ShowCaseWidget(
  child: Somewidget(),
),

GlobalKey _one = GlobalKey();
GlobalKey _two = GlobalKey();
GlobalKey _three = GlobalKey();

...

Showcase(
  key: _one,
  title: 'Menu',
  description: 'Click here to see menu options',
  child: Icon(
    Icons.menu,
    color: Colors.black45,
  ),
),

Showcase(
  key: _two,
  title: 'Profile',
  description: 'Click here to go to your Profile',
  shapeBorder: CircleBorder(),
  showArrow: false,
  slideDuration: Duration(milliseconds: 1500),
  tooltipColor: Colors.blueGrey,
  child: ...,
),

Showcase.withWidget(
  key: _three,
  cHeight: 80,
  cWidth: 140,
  shapeBorder: CircleBorder(),
  container: Column(
    crossAxisAlignment: CrossAxisAlignment.start,
    children: <Widget>[
      ...
    ],
  ),
  child: ...,
),

someEvent(){
    ShowCaseWidget.startShowCase(context, [_one, _two, _three]);
}

WidgetsBinding.instance.addPostFrameCallback((_) =>
        ShowCaseWidget.startShowCase(context, [_one, _two, _three]));