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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
3.1 KiB
Dart
93 lines
3.1 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/stateful_widget_material.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 AnimatedSwitcher
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//
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//***************************************************************************
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//* ▼▼▼▼▼▼▼▼ description ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)
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// This sample shows a counter that animates the scale of a text widget
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// whenever the value changes.
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//* ▲▲▲▲▲▲▲▲ description ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
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//***************************************************************************
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import 'package:flutter/material.dart';
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void main() => runApp(const MyApp());
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/// This is the main application widget.
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class MyApp extends StatelessWidget {
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const MyApp({Key? key}) : super(key: key);
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static const String _title = 'Flutter Code Sample';
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@override
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Widget build(BuildContext context) {
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return const MaterialApp(
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title: _title,
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home: MyStatefulWidget(),
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);
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}
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}
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/// This is the stateful widget that the main application instantiates.
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class MyStatefulWidget extends StatefulWidget {
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const MyStatefulWidget({Key? key}) : super(key: key);
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@override
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State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
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}
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/// This is the private State class that goes with MyStatefulWidget.
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class _MyStatefulWidgetState extends State<MyStatefulWidget> {
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//********************************************************************
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//* ▼▼▼▼▼▼▼▼ code ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)
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int _count = 0;
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@override
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Widget build(BuildContext context) {
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return Container(
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color: Colors.white,
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child: Column(
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mainAxisAlignment: MainAxisAlignment.center,
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children: <Widget>[
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AnimatedSwitcher(
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duration: const Duration(milliseconds: 500),
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transitionBuilder: (Widget child, Animation<double> animation) {
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return ScaleTransition(child: child, scale: animation);
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},
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child: Text(
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'$_count',
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// This key causes the AnimatedSwitcher to interpret this as a "new"
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// child each time the count changes, so that it will begin its animation
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// when the count changes.
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key: ValueKey<int>(_count),
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style: Theme.of(context).textTheme.headline4,
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),
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),
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ElevatedButton(
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child: const Text('Increment'),
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onPressed: () {
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setState(() {
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_count += 1;
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});
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},
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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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}
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