mirror of https://github.com/flutter/samples.git
79 lines
2.5 KiB
79 lines
2.5 KiB
// Copyright 2019 The Flutter team. 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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class AnimatedBuilderDemo extends StatefulWidget {
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const AnimatedBuilderDemo({super.key});
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static const String routeName = '/basics/animated_builder';
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@override
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State<AnimatedBuilderDemo> createState() => _AnimatedBuilderDemoState();
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}
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class _AnimatedBuilderDemoState extends State<AnimatedBuilderDemo>
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with SingleTickerProviderStateMixin {
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static const Color beginColor = Colors.deepPurple;
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static const Color endColor = Colors.deepOrange;
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Duration duration = const Duration(milliseconds: 800);
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late AnimationController controller;
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late Animation<Color?> animation;
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@override
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void initState() {
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super.initState();
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controller = AnimationController(vsync: this, duration: duration);
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animation =
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ColorTween(begin: beginColor, end: endColor).animate(controller);
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}
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@override
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void dispose() {
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controller.dispose();
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super.dispose();
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}
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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('AnimatedBuilder'),
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),
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body: Center(
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// AnimatedBuilder handles listening to a given animation and calling the builder
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// whenever the value of the animation change. This can be useful when a Widget
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// tree contains some animated and non-animated elements, as only the subtree
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// created by the builder needs to be re-built when the animation changes.
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child: AnimatedBuilder(
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animation: animation,
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builder: (context, child) {
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return MaterialButton(
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color: animation.value,
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height: 50,
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minWidth: 100,
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child: child,
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onPressed: () {
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if (controller.status == AnimationStatus.completed) {
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controller.reverse();
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} else {
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controller.forward();
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}
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},
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);
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},
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// AnimatedBuilder can also accept a pre-built child Widget which is useful
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// if there is a non-animated Widget contained within the animated widget.
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// This can improve performance since this widget doesn't need to be rebuilt
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// when the animation changes.
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child: const Text(
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'Change Color',
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style: TextStyle(color: Colors.white),
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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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