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在Flutter开发当中，如果我们不需要实现单独的继承AnimatedWidget自定义动画组件，我们可以通过AnimatedBuilder组件来实现相同效果的动画。这篇博客分享AnimatedBuilder组件的简单使用，希望对看文章的小伙伴有所帮助。

AnimatedBuilder简单用法

核心代码：

AnimatedBuilder(
        animation: controller,
        builder: (BuildContext context, Widget? child) {
          return Container(
            height: 200,
            padding: const EdgeInsets.all(10),
            margin: const EdgeInsets.all(10),
            decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: LinearGradient(
                    begin: Alignment.topCenter,
                    end: Alignment.bottomCenter,
                    colors: const [Colors.yellow, Colors.red],
                    stops: [0, controller.value])),
          );
        },
      )

完整代码：

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: '动画 Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  late Animation<double> animation;
  late AnimationController controller;

  @override
  void initState() {
    super.initState();
    controller =
        AnimationController(duration: const Duration(seconds: 1), vsync: this);
    animation = Tween<double>(begin: 0, end: 1.0).animate(controller);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: AnimatedBuilder(
        animation: controller,
        builder: (BuildContext context, Widget? child) {
          return Container(
            height: 200,
            padding: const EdgeInsets.all(10),
            margin: const EdgeInsets.all(10),
            decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: LinearGradient(
                    begin: Alignment.topCenter,
                    end: Alignment.bottomCenter,
                    colors: const [Colors.yellow, Colors.red],
                    stops: [0, controller.value])),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // 点击事件,设置动画开始
          if (controller.status == AnimationStatus.completed) {
            controller.reverse();
          } else {
            controller.forward();
          }
        },
        child: const Icon(Icons.play_arrow),
      ),
    );
  }

  @override
  void dispose() {
    super.dispose();
    controller.dispose();
  }
}

实现的效果如下，两种效果可以通过右下角的按钮来切换：

效果1

效果2