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Add some cross references in the docs, move an example to a dartpad example (#145571)
## Description This adds some "See also" links to some docs for `TweenAnimationBuilder` and `ValueListenableBuilder`. Also, moved a "snippet" example in `ValueListenableBuilder` into the examples directory as a Dartpad example. ## Tests - Added test for the example.
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// 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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import 'package:flutter/material.dart';
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/// Flutter code sample for [ValueListenableBuilder].
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void main() => runApp(const ValueListenableBuilderExampleApp());
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class ValueListenableBuilderExampleApp extends StatelessWidget {
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const ValueListenableBuilderExampleApp({super.key});
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@override
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Widget build(BuildContext context) {
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return const MaterialApp(
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home: ValueListenableBuilderExample(),
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);
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}
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}
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class ValueListenableBuilderExample extends StatefulWidget {
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const ValueListenableBuilderExample({super.key});
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@override
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State<ValueListenableBuilderExample> createState() => _ValueListenableBuilderExampleState();
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}
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class _ValueListenableBuilderExampleState extends State<ValueListenableBuilderExample> {
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final ValueNotifier<int> _counter = ValueNotifier<int>(0);
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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appBar: AppBar(
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title: const Text('ValueListenableBuilder Sample'),
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),
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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('You have pushed the button this many times:'),
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ValueListenableBuilder<int>(
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builder: (BuildContext context, int value, Widget? child) {
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// This builder will only get called when the _counter
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// is updated.
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return Row(
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mainAxisAlignment: MainAxisAlignment.center,
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crossAxisAlignment: CrossAxisAlignment.start,
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children: <Widget>[
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CountDisplay(count: value),
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child!,
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],
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);
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},
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valueListenable: _counter,
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// The child parameter is most helpful if the child is
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// expensive to build and does not depend on the value from
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// the notifier.
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child: const Padding(
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padding: EdgeInsets.all(10.0),
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child: SizedBox(
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width: 40,
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height: 40,
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child: FlutterLogo(size: 40),
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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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floatingActionButton: FloatingActionButton(
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child: const Icon(Icons.plus_one),
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onPressed: () => _counter.value += 1,
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),
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);
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}
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}
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class CountDisplay extends StatelessWidget {
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const CountDisplay({super.key, required this.count});
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final int count;
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@override
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Widget build(BuildContext context) {
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return Container(
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width: 100,
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height: 100,
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padding: const EdgeInsetsDirectional.all(10),
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child: Text('$count', style: Theme.of(context).textTheme.headline4),
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);
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}
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}
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@ -0,0 +1,35 @@
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// 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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import 'package:flutter/material.dart';
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import 'package:flutter_api_samples/widgets/value_listenable_builder/value_listenable_builder.0.dart' as example;
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import 'package:flutter_test/flutter_test.dart';
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void main() {
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testWidgets('Tapping FAB increments counter', (WidgetTester tester) async {
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await tester.pumpWidget(
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const MaterialApp(
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home: example.ValueListenableBuilderExample(),
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),
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);
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String getCount() {
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return (tester.widget(
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find.descendant(
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of: find.byType(example.CountDisplay),
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matching: find.byType(Text),
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),
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) as Text).data!;
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}
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expect(find.text('You have pushed the button this many times:'), findsOneWidget);
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expect(find.text('0'), findsOneWidget);
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expect(find.byIcon(Icons.plus_one), findsOneWidget);
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expect(getCount(), equals('0'));
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await tester.tap(find.byType(FloatingActionButton).first);
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await tester.pumpAndSettle();
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expect(getCount(), equals('1'));
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});
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}
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@ -90,6 +90,11 @@ import 'value_listenable_builder.dart';
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/// [AnimatedBuilder], which can be used similarly to this
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/// [TweenAnimationBuilder], but unlike the latter it is powered by a
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/// developer-managed [AnimationController].
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///
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/// See also:
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///
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/// * [ValueListenableBuilder], a widget whose content stays synced with a
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/// [ValueListenable] instead of a [Tween].
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class TweenAnimationBuilder<T extends Object?> extends ImplicitlyAnimatedWidget {
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/// Creates a [TweenAnimationBuilder].
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///
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@ -40,63 +40,11 @@ typedef ValueWidgetBuilder<T> = Widget Function(BuildContext context, T value, W
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/// Using this pre-built child is entirely optional, but can improve
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/// performance significantly in some cases and is therefore a good practice.
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///
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/// {@tool snippet}
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///
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/// {@tool dartpad}
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/// This sample shows how you could use a [ValueListenableBuilder] instead of
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/// setting state on the whole [Scaffold] in the default `flutter create` app.
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/// setting state on the whole [Scaffold] in a counter app.
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///
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/// ```dart
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/// class MyHomePage extends StatefulWidget {
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/// const MyHomePage({super.key, required this.title});
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/// final String title;
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///
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/// @override
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/// State<MyHomePage> createState() => _MyHomePageState();
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/// }
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///
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/// class _MyHomePageState extends State<MyHomePage> {
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/// final ValueNotifier<int> _counter = ValueNotifier<int>(0);
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/// final Widget goodJob = const Text('Good job!');
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/// @override
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/// Widget build(BuildContext context) {
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/// return Scaffold(
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/// appBar: AppBar(
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/// title: Text(widget.title)
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/// ),
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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('You have pushed the button this many times:'),
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/// ValueListenableBuilder<int>(
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/// builder: (BuildContext context, int value, Widget? child) {
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/// // This builder will only get called when the _counter
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/// // is updated.
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/// return Row(
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/// mainAxisAlignment: MainAxisAlignment.spaceEvenly,
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/// children: <Widget>[
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/// Text('$value'),
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/// child!,
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/// ],
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/// );
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/// },
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/// valueListenable: _counter,
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/// // The child parameter is most helpful if the child is
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/// // expensive to build and does not depend on the value from
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/// // the notifier.
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/// child: goodJob,
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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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/// child: const Icon(Icons.plus_one),
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/// onPressed: () => _counter.value += 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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/// ** See code in examples/api/lib/widgets/value_listenable_builder/value_listenable_builder.0.dart **
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/// {@end-tool}
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///
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/// See also:
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/// you have a direct reference to.
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/// * [StreamBuilder], where a builder can depend on a [Stream] rather than
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/// a [ValueListenable] for more advanced use cases.
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/// * [TweenAnimationBuilder], which can animate values in a widget based on a
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/// [Tween].
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class ValueListenableBuilder<T> extends StatefulWidget {
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/// Creates a [ValueListenableBuilder].
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///
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