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This extracts the sample code out from the API doc comments, and places them in separate files on disk, allowing running of the examples locally, testing them, and building of slightly larger examples.
93 lines
3.3 KiB
Dart
93 lines
3.3 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Template: dev/snippets/config/templates/freeform.tmpl
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//
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// Comment lines marked with "▼▼▼" and "▲▲▲" are used for authoring
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// of samples, and may be ignored if you are just exploring the sample.
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// Flutter code sample for ScaffoldMessenger.of
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//
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//***************************************************************************
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//* ▼▼▼▼▼▼▼▼ description ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)
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// Sometimes [SnackBar]s are produced by code that doesn't have ready access
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// to a valid [BuildContext]. One such example of this is when you show a
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// SnackBar from a method outside of the `build` function. In these
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// cases, you can assign a [GlobalKey] to the [ScaffoldMessenger]. This
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// example shows a key being used to obtain the [ScaffoldMessengerState]
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// provided by the [MaterialApp].
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//* ▲▲▲▲▲▲▲▲ description ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
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//***************************************************************************
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//****************************************************************************
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//* ▼▼▼▼▼▼▼▼ code-imports ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)
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import 'package:flutter/material.dart';
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//* ▲▲▲▲▲▲▲▲ code-imports ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
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//****************************************************************************
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//********************************************************************
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//* ▼▼▼▼▼▼▼▼ code ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)
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void main() => runApp(const MyApp());
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class MyApp extends StatefulWidget {
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const MyApp({Key? key}) : super(key: key);
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@override
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State<MyApp> createState() => _MyAppState();
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}
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class _MyAppState extends State<MyApp> {
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final GlobalKey<ScaffoldMessengerState> _scaffoldMessengerKey =
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GlobalKey<ScaffoldMessengerState>();
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int _counter = 0;
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void _incrementCounter() {
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setState(() {
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_counter++;
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});
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if (_counter % 10 == 0) {
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_scaffoldMessengerKey.currentState!.showSnackBar(const SnackBar(
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content: Text('A multiple of ten!'),
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));
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}
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}
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@override
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Widget build(BuildContext context) {
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return MaterialApp(
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scaffoldMessengerKey: _scaffoldMessengerKey,
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home: Scaffold(
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appBar: AppBar(title: const Text('ScaffoldMessenger Demo')),
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body: Center(
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child: Column(
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mainAxisAlignment: MainAxisAlignment.center,
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children: <Widget>[
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const Text(
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'You have pushed the button this many times:',
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),
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Text(
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'$_counter',
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style: Theme.of(context).textTheme.headline4,
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),
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],
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),
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),
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floatingActionButton: FloatingActionButton(
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onPressed: _incrementCounter,
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tooltip: 'Increment',
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child: const Icon(Icons.add),
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),
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),
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);
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}
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}
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//* ▲▲▲▲▲▲▲▲ code ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
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//********************************************************************
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