Flutter动画关键帧插件keyframe的使用

通过将Tweens转换为带有关键帧的Timeline，可以改善Flutter中的动画体验，就像视频编辑器一样，但使用编程语言来实现。

示例代码

example/lib/main.dart

import 'dart:convert';
import 'dart:developer';

import 'package:flutter/material.dart';
import 'package:keyframe/keyframe.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // 这个小部件是你的应用的根。
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  late final AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(seconds: 2),
      vsync: this,
    );

    _controller.addListener(() {
      setState(() {});
    });
  }

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

  final bool _initialized = false;

  init() {
    if (_initialized) return;
    registerExtension('ext.keyframe.up', (method, parameters) async {
      return ServiceExtensionResponse.result(
        jsonEncode({
          'index': 1,
          'value': 2,
        }),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    final timeline = Timeline(
      properties: [
        KeyframeProperty<Color>(
          [
            Keyframe<Color>(0, Colors.red),
            Keyframe<Color>(0.5, Colors.green),
            Keyframe<Color>(0.7, Colors.blue),
            Keyframe<Color>(1, Colors.red),
          ],
        ),
        KeyframeProperty<Size>(
          [
            Keyframe(0, const Size(200, 200)),
            Keyframe(0.5, const Size(300, 200)),
            Keyframe(0.7, const Size(300, 300)),
            Keyframe(1.0, const Size(200, 200)),
          ],
        ),
      ],
    ).animate(_controller);

    final color = timeline.value<Color>();
    final size = timeline.value<Size>();

    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Container(
              width: size.width,
              height: size.height,
              color: color,
            ),
            const Text(
              '你已经点击了按钮很多次：',
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          _controller.reset();
          _controller.forward();
          init();
          print(extensionStreamHasListener);
          postEvent('ext.keyframe', {
            'test': 'dsfdfd',
          });
        },
        tooltip: '增加',
        child: const Icon(Icons.add),
      ),
    );
  }
}

代码解释

1. 导入必要的库

   import 'dart:convert';
   import 'dart:log';
   import 'package:flutter/material.dart';
   import 'package:keyframe/keyframe.dart';
   

2. 创建主应用类

   class MyApp extends StatelessWidget {
     const MyApp({super.key});
   
     @override
     Widget build(BuildContext context) {
       return MaterialApp(
         title: 'Flutter Demo',
         theme: ThemeData(
           colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
           useMaterial3: true,
         ),
         home: const MyHomePage(title: 'Flutter Demo Home Page'),
       );
     }
   }
   

3. 创建主页状态管理类

   class MyHomePage extends StatefulWidget {
     const MyHomePage({super.key, required this.title});
   
     final String title;
   
     @override
     State<MyHomePage> createState() => _MyHomePageState();
   }
   

4. 初始化控制器

   class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
     late final AnimationController _controller;
   
     @override
     void initState() {
       super.initState();
       _controller = AnimationController(
         duration: const Duration(seconds: 2),
         vsync: this,
       );
   
       _controller.addListener(() {
         setState(() {});
       });
     }
   

5. 定义关键帧属性

   final timeline = Timeline(
     properties: [
       KeyframeProperty<Color>(
         [
           Keyframe<Color>(0, Colors.red),
           Keyframe<Color>(0.5, Colors.green),
           Keyframe<Color>(0.7, Colors.blue),
           Keyframe<Color>(1, Colors.red),
         ],
       ),
       KeyframeProperty<Size>(
         [
           Keyframe(0, const Size(200, 200)),
           Keyframe(0.5, const Size(300, 200)),
           Keyframe(0.7, const Size(300, 300)),
           Keyframe(1.0, const Size(200, 200)),
         ],
       ),
     ],
   ).animate(_controller);
   

6. 设置UI组件

   return Scaffold(
     appBar: AppBar(
       backgroundColor: Theme.of(context).colorScheme.inversePrimary,
       title: Text(widget.title),
     ),
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: [
           Container(
             width: size.width,
             height: size.height,
             color: color,
           ),
           const Text(
             '你已经点击了按钮很多次：',
           ),
         ],
       ),
     ),
     floatingActionButton: FloatingActionButton(
       onPressed: () {
         _controller.reset();
         _controller.forward();
         init();
         print(extensionStreamHasListener);
         postEvent('ext.keyframe', {
           'test': 'dsfdfd',
         });
       },
       tooltip: '增加',
       child: const Icon(Icons.add),
     ),
   );