【Flutter入门到进阶】Flutter基础篇---动画

1 动画基本原理以及Flutter动画简介

1.1 动画原理

        在任何系统的UI框架中，动画实现的原理都是相同的，即：在一段时间内，快速地多次改变UI外观；由 于人眼会产生视觉暂留，所以最终看到的就是一个“连续”的动画，这和电影的原理是一样的。

        我们将UI 的一次改变称为一个动画帧，对应一次屏幕刷新，屏幕刷新率，而决定动画流畅度的一个重要指标就是帧率FPS  ( Frame Per Second)，即每秒的动画帧数，体现为每秒能生产图片的多少。

        很明显，帧率越高则动画就会越流畅！一般情况下， 对于人眼来说，动画帧率超过16 FPS，就基本能看了，超过 32 FPS就会感觉相对平滑，而超过 32 FPS，大多数人基本上就感受不到差别了。

        由于动画的每一帧都是要改变UI输出，所以在一个时间段内 连续的改变UI输出是比较耗资源的，对设备的软硬件系统要求都较高，所以在UI系统中，动画的平均帧 率是重要的性能指标，而在Flutter中，理想情况下是可以实现 60FPS 的，这和原生应用能达到的帧率是基本是持平的。

1.2 Flutter动画简介

1.2.1 FLutter中的动画主要分为：

        隐式动画

        显式动画

        自定义隐式动画、自定义显式动画

        Hero 动画

2 隐式动画

2.1 说明

        通过几行代码就可以实现隐式动画，由于隐式动画背后的实现原理和繁琐的操作细节都被隐去了，所以 叫隐式动画，  Flutter中提供的 AnimatedContainer、AnimatedPadding、AnimatedPositioned、AnimatedOpacity、AnimatedDefaultTextStyle、AnimatedSwitcher都属于隐式动画。

        隐式动画中可以通过 duration配置动画时长、可以通过 Curve (曲线)来配置动画过程

2.2 AnimatedContainer

2.2.1 概述

        AnimatedContainer的属性和Container属性基本是一样的，当AnimatedContainer属性改变的时候就会触发动画。

2.2.2 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 const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.animation),
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
      ),
      appBar: AppBar(
        title: const Text("AnimatedContainer Demo"),
      ),
      body: Center(
        child: AnimatedContainer(
          duration: const Duration(milliseconds: 500),
          // 动画时长500 ms width: flag?100:300,
          height: flag ? 100 : 300,
          color: Colors.blue,
        ),
      ),
    );
  }
}

2.3 AnimatedPadding以及curve属性

2.3.1 Curves曲线值

linear        匀速的

decelerate        匀减速

ease        开始加速，后面减速

easeIn        开始慢，后面快

easeOut        开始快，后面慢

easeInOut        开始慢，然后加速，最后再减速

更多曲线        https://docs.flutter.io/flutter/animation/Curves-class.html

2.3.2 示例

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 const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.animation),
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
      ),
      appBar: AppBar(
        title: const Text("AnimatedContainer Demo"),
      ),
      body: AnimatedPadding(
        duration: const Duration(milliseconds: 2000),
        // 动画时长500 ms curve: Curves.bounceInOut,
        padding: EdgeInsets.fromLTRB(10, flag ? 10 : 500, 0, 0),

        child: Container(
          width: 100,
          height: 100,
          color: Colors.red,
        ),
      ),
    );
  }
}

2.4 AnimatedPositioned

2.4.1 示例

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  MyHomePageState createState() => MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Stack(
        children: [
          AnimatedPositioned(
            curve: Curves.easeInOut,
            duration: const Duration(seconds: 1),
            top: flag ? 10 : 500,
            left: flag ? 10 : 300,
            child: Container(
              width: 60,
              height: 60,
              color: Colors.blue,
            ),
          ),
          Align(
            alignment: const Alignment(0, 0.8),
            child: ElevatedButton(
              child: const Text("Transform"),
              onPressed: () {
                setState(() {
                  flag = !flag;
                });
              },
            ),
          ),
        ],
      ),
    );
  }
}

2.5 AnimatedOpacity

2.5.1 示例

import 'dart:isolate';
import 'dart:math';

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {


    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  MyHomePageState createState() => MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  bool flag = true;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: (){
          setState(() {
            flag= !flag;
          });
        },
        child: const Icon(Icons.opacity),
      ),
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Center(
        child: AnimatedOpacity(
          curve: Curves.linear,
          duration: const Duration(seconds: 1),
          opacity: flag?1:0,
          child: Container(
            width: 300,
            height: 300,
            color: Colors.blue,
          ),
        ),
      ),
    );
  }
}

2.6 AnimatedDefaultTextStyle

2.6.1 示例

import 'dart:isolate';
import 'dart:math';

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
        child: const Icon(Icons.opacity),
      ),
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Center(
        child: Container(
          alignment: Alignment.center,
          width: 300,
          height: 300,
          color: Colors.blue,
          child: AnimatedDefaultTextStyle(
            duration: const Duration(seconds: 1),
            style: TextStyle(
              fontSize: flag ? 20 : 50,
            ),
            child: const Text("你好Flutte"),
          ),
        ),
      ),
    );
  }
}

2.7 AnimatedSwitcher 以及transitionBuilder

2.7.1 说明

        AnimatedContainer、AnimatedPadding、AnimatedPositioned、AnimatedOpacity、AnimatedDefaultTextStyle都是在属性改变的时候执行动画，  AnimatedSwitcher则是在子元素改变的 时候执行动画。

        相比上面的动画组件AnimatedSwitcher多了transitionBuilder参数，可以在transitionBuilder中自定义 动画

2.7.2 示例

示例1：载页面前显示一个loading动画，加载完毕后显示对于的内容

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
        child: const Icon(Icons.opacity),
      ),
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Center(
        child: Container(
          alignment: Alignment.center,
          width: 300,
          height: 180,
          color: Colors.yellow,
          child: AnimatedSwitcher(
            duration: const Duration(milliseconds: 1000),
            child: flag
                ? const CircularProgressIndicator()
                : Image.asset(
                    "images/2.png",
                    fit: BoxFit.contain,
                  ),
          ),
        ),
      ),
    );
  }
}

示例2：通过transitionBuilder自定义动画效果

import 'dart:isolate';
import 'dart:math';

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
        child: const Icon(Icons.opacity),
      ),
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Center(
        child: Container(
          alignment: Alignment.center,
          width: 300,
          height: 180,
          color: Colors.yellow,
          child: AnimatedSwitcher(
            transitionBuilder: ((child, animation) {
              return ScaleTransition(
                scale: animation,
                child: FadeTransition(
                  opacity: animation,
                  child: child,
                ),
              );
            }),
            duration: const Duration(milliseconds: 400),
            child: flag
                ? const CircularProgressIndicator()
                : Image.asset(
                    "images/2.png",
                    fit: BoxFit.contain,
                  ),
          ),
        ),
      ),
    );
  }
}

示例3：通过transitionBuilder改变子元素执行动画

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );


  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
        child: const Icon(Icons.opacity),
      ),
      appBar: AppBar(
        title: const Text("AnimatedPositioned Demo"),
      ),
      body: Center(
        child: Container(
          alignment: Alignment.center,
          width: 300,
          height: 180,
          color: Colors.yellow,
          child: AnimatedSwitcher(
            transitionBuilder: ((child, animation) {
              return  ScaleTransition(
                scale: animation,
                child: FadeTransition(
                  opacity: animation,
                  child:child ,
                ),
              );
            }),
            duration: const Duration(milliseconds: 400),
            child: Text(key:UniqueKey(),flag?"你好Flutter":"你好大地",style: const TextStyle(fontSize: 30),),
          ),
        ),
      ),
    );
  }
}

3 显式动画

3.1 说明

        常见的显式动画有RotationTransition、FadeTransition、ScaleTransition、SlideTransition、AnimatedIcon。在显示动画中开发者需要创建一个AnimationController，通过AnimationController 控制动画的开始、暂停、重置、跳转、倒播等

3.2 RotationTransition、   AnimationController

示例1：AnimationController普通用法

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    // TODO: implement initState
    _controller = AnimationController(
      // Vsync 机制可以理解为是显卡与显示器的通信桥梁，显卡在渲染每一帧之前会等待垂直同步信号，
      // 只有显示器完成了一次刷新时，发出垂直同步信号，显卡才会渲染下一帧，确保刷新率和帧率保
      // 持同步，以达到供需平衡的效果，防止卡顿现象。
        vsync:
        this,
    duration: const Duration(seconds: 1),);
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(

      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          RotationTransition(
            turns: _controller,
            child: const FlutterLogo(
              size: 100,
            ),
          ),
          const SizedBox(height: 40,),
          Padding(padding: const EdgeInsets.fromLTRB(10, 0, 0, 0), child: Wrap(
            spacing: 10,
            alignment: WrapAlignment.center,
            children: [
              ElevatedButton(onPressed: () {
                _controller.forward(); //正序播放一次
              }, child: const Text("Forward")),
              ElevatedButton(onPressed: () {
                _controller.reverse(); //倒序播放一次
              }, child: const Text("Reverse")),
              ElevatedButton(onPressed: () {
                _controller.stop(); //停止播放
              }, child: const Text("Stop")),
              ElevatedButton(onPressed: () {
                _controller.reset(); //重置
              }, child: const Text("rest")),
              ElevatedButton(onPressed: () {
                _controller.repeat(); //重复播放
              }, child: const Text("repeat"))
            ],
          ),)
        ],
      ),
    );
  }
}

示例2：  lowerBound upperBound

        AnimationController 用于控制动画，它包含动画的启动 forward() 、停止 stop() 、反向播放 reverse() 等方法。 AnimationController 会在动画的每一帧，就会生成一个新的值。默认情况 下， AnimationController 在给定的时间段内线性的生成从 0.0 到1.0（默认区间）的数字 ，我们也 可以通过 lowerbound 和 upperBound 来修改 AnimationController 生成数字的区间。

代码

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
// TODO: implement initState

    _controller = AnimationController(
        vsync: this,
        duration: const Duration(seconds: 1),
        lowerBound: 3, //第三圈转到第五圈
        upperBound: 5);

    _controller.addListener(() {
      print(_controller.value);
    });
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          RotationTransition(
            turns: _controller,
            child: const FlutterLogo(
              size: 100,
            ),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Wrap(
              spacing: 10,
              alignment: WrapAlignment.center,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
                ElevatedButton(
                    onPressed: () {
                      _controller.stop(); //停止播放
                    },
                    child: const Text("Stop")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reset(); //重置
                    },
                    child: const Text("rest")),
                ElevatedButton(
                    onPressed: () {
                      _controller.repeat(); //重复播放
                    },
                    child: const Text("repeat"))
              ],
            ),
          )
        ],
      ),
    );
  }
}

3.3 FadeTransition

3.3.1 示例

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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {

    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          FadeTransition(
            opacity: _controller,
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

3.4 ScaleTransition、Tween

3.4.1 示例1:AnimationController控制动画

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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
// TODO: implement initState

    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          ScaleTransition(
            scale: _controller,
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

3.4.2 示例2：AnimationController结合Tween控制动画

说明

默认情况下，   AnimationController对象值的范围是[0.0 ，  1.0]。如果我们需要构建UI的动画值在不同 的范围或不同的数据类型，则可以使用 Tween来添加映射以生成不同的范围或数据类型的值

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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    // TODO: implement initState
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          ScaleTransition(
            scale: _controller.drive(Tween(begin: 1, end: 2)),
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

3.5 SlideTransition

3.5.1 说明

        这是一负责平移的显示动画组件，使用时需要通过position属性传入一个Animated表示位移程度，通常 借助Tween实现

3.5.2 示例

示例1：_controller.drive驱动动画

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          SlideTransition(
              position: _controller.drive(
                  Tween(
                    begin: const Offset(0, 0),
                    end: const Offset(1.2, 0),
                  ),
              ),
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

示例2：Tween.animate 驱动动画

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();

    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          SlideTransition(
            position: Tween(
                    begin: const Offset(0, 0),
                    end: const Offset(1.2, 0) //表示实际的位置向右移动自身宽度的1.2倍
                    )
                .animate(_controller),
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

示例3：   链式操作修改动画效果

Curve：动画曲线，作用和Android中的Interpolator（差值器）类似，负责控制动画变化的速率，通俗地讲就是使动画的效果能够以匀速、加速、减速、抛物线等各种速率变化。

Tween：将 AnimationController 生成的 [0,1]值映射成其他属性的值，比如颜色、样式等。

https://www.jianshu.com/p/ef1b6212bcb8

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
// TODO: implement initState

    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 1),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          SlideTransition(
            position:
                Tween(begin: const Offset(0, -1), end: const Offset(0, 0.8))
                    .chain(CurveTween(curve: Curves.bounceIn))
                    .animate(_controller),
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

示例4：   链式操作修改动动画执行时间

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
// TODO: implement initState

    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 3),
    );
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          SlideTransition(
            position:
                Tween(begin: const Offset(0, -1), end: const Offset(0, 0.8))
                    .chain(CurveTween(curve: Curves.bounceIn))
                    .chain(CurveTween(curve: const Interval(0.8, 1.0)))
                    .animate(_controller),
            child: const FlutterLogo(size: 80),
          ),
          const SizedBox(
            height: 40,
          ),
          Padding(
            padding: const EdgeInsets.fromLTRB(10, 0, 0, 0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                ElevatedButton(
                    onPressed: () {
                      _controller.forward(); //正序播放一次
                    },
                    child: const Text("Forward")),
                ElevatedButton(
                    onPressed: () {
                      _controller.reverse(); //倒序播放一次
                    },
                    child: const Text("Reverse")),
              ],
            ),
          )
        ],
      ),
    );
  }
}

4 AnimatedIcon

4.1 说明

        AnimatedIcon顾名思义，是一个用于提供动画图标的组件，它的名字虽然是以Animated开头，但是他 是一个显式动画组件，需要通过progress属性传入动画控制器，另外需要由Icon属性传入动画图标数据

4.2 示例

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 const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 1));
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.add),
        onPressed: () {
          _controller.forward();
        },
      ),
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Center(
        child: AnimatedIcon(
            icon: AnimatedIcons.menu_close, progress: _controller, size: 40),
      ),
    );
  }
}

5 交错动画

5.1 示例

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  bool flag = true;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 6),
    )..repeat(reverse: true);
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.refresh),
        onPressed: () {
          flag ? _controller.forward() : _controller.reverse();
          flag = !flag;
        },
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            SlidingBox(
              controller: _controller,
              color: Colors.blue[200],
              curve: const Interval(0, 0.2),
            ),
            SlidingBox(
              controller: _controller,
              color: Colors.blue[400],
              curve: const Interval(0.2, 0.4),
            ),
            SlidingBox(
              controller: _controller,
              color: Colors.blue[600],
              curve: const Interval(0.4, 0.6),
            ),
            SlidingBox(
              controller: _controller,
              color: Colors.blue[800],
              curve: const Interval(0.6, 0.8),
            ),
            SlidingBox(
              controller: _controller,
              color: Colors.blue[900],
              curve: const Interval(0.8, 1.0),
            ),
          ],
        ),
      ),
    );
  }
}

class SlidingBox extends StatelessWidget {
  final AnimationController controller;
  final Color? color;
  final Curve curve;

  const SlidingBox(
      {super.key,
      required this.controller,
      required this.color,
      required this.curve});

  @override
  Widget build(BuildContext context) {
    return SlideTransition(
      position: Tween(begin: const Offset(0, 0), end: const Offset(0.3, 0))
          .chain(CurveTween(curve: Curves.bounceInOut))
          .chain(CurveTween(curve: curve))
          .animate(controller),
      child: Container(
        width: 220,
        height: 60,
        color: color,
      ),
    );
  }
}

6 自定义动画

6.1 TweenAnimationBuilder自定义隐式动画

6.1.1 每当Tween的end发生变化的时候就会触发动画

6.1.2 示例1：大小变化

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.refresh),
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
      ),
      body: Center(
        child: TweenAnimationBuilder(
            tween: Tween(begin: 100.0, end: flag ? 100.0 : 200.0),
            duration: const Duration(seconds: 1),
            builder: ((context, value, child) {
              return Icon(
                Icons.star,
                size: value,
              );
            })),
      ),
    );
  }
}

6.1.3 示例2：透明度变化

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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.refresh),
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
      ),
      body: Center(
        child: TweenAnimationBuilder(
            tween: Tween(begin: 0.0, end: flag ? 0.0 : 1.0),
            duration: const Duration(seconds: 1),
            builder: ((context, value, child) {
              return Opacity(
                opacity: value,
                child: Container(
                  color: Colors.red,
                  width: 200,
                  height: 200,
                ),
              );
            })),
      ),
    );
  }
}

6.2 AnimatedBuilder 自定义显式动画

6.2.1 示例1：透明度动画

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(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 1))
          ..repeat(reverse: true);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Center(
        child: AnimatedBuilder(
          animation: _controller,
          builder: (BuildContext context, Widget? child) {
            return Opacity(
              opacity: _controller.value, //从0到1的变化
              child: Container(
                width: 200,
                height: 200,
                color: Colors.red,
                child: const Text("我是一个text组件"),
              ),
            );
          },
        ),
      ),
    );
  }
}

6.2.2 示例2：自定义变化范围

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 1))
          ..repeat(reverse: true);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Center(
        child: AnimatedBuilder(
          animation: _controller,
          builder: (BuildContext context, Widget? child) {
            return Opacity(
              opacity: Tween(begin: 0.5, end: 1.0)
                  .animate(_controller)
                  .value, //从0.5到1的变化

              child: Container(
                width: 200,
                height: 200,
                color: Colors.red,
                child: const Text("我是一个text组件"),
              ),
            );
          },
        ),
      ),
    );
  }
}

6.2.3 示例3：位置变化

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 1))
          ..repeat(reverse: true);
  }

  @override
  Widget build(BuildContext context) {
    Animation x = Tween(begin: -100.0, end: 100.0)
        .chain(CurveTween(curve: Curves.easeIn))
        .chain(CurveTween(curve: const Interval(0.2, 0.8)))
        .animate(_controller);
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Center(
        child: AnimatedBuilder(
          animation: _controller,
          builder: (BuildContext context, Widget? child) {
            return Container(
              width: 200,
              height: 200,
              color: Colors.red,
              transform: Matrix4.translationValues(x.value, 0, 0),
              child: const Text("我是一个text组件"),
            );
          },
        ),
      ),
    );
  }
}

6.2.4 示例4：chilid优化

import 'package:flutter/material.dart';

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

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

// This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

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

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 1))
          ..repeat(reverse: true);
  }

  @override
  Widget build(BuildContext context) {
    Animation x = Tween(begin: -100.0, end: 100.0)
        .chain(CurveTween(curve: Curves.easeIn))
        .chain(CurveTween(curve: const Interval(0.2, 0.4)))
        .animate(_controller);
    return Scaffold(
      appBar: AppBar(
        title: const Text('Title'),
      ),
      body: Center(
        child: AnimatedBuilder(
          animation: _controller,
          builder: (BuildContext context, Widget? child) {
            return Container(
              width: 200,
              height: 200,
              color: Colors.red,
              transform: Matrix4.translationValues(x.value, 0, 0),
              child: child,
            );
          },
          child: const Text("我是一个text组件"),
        ),
      ),
    );
  }
}

7 Hero 动画

7.1 Hero 动画的使用

        微信朋友圈点击小图片的时候会有一个动画效果到大图预览，这个动画效果就可以使用Hero 动画实 现。

        Hero 指的是可以在路由(页面)之间“飞行”的 widget，简单来说 Hero 动画就是在路由切换时，有一个共 享的widget 可以在新旧路由间切换。

7.2 示例

import 'package:flutter/material.dart';
import '../../res/listData.dart';
import 'hero.dart';
import 'hero2.dart';

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Widget> _getListData() {
    var tempList = listData2.map((value) {
      return GestureDetector(
        onTap: () {
          Navigator.push(context, MaterialPageRoute(builder: (setting) {
            // return HeroPage(arguments: {
            //   "imageUrl": value['imageUrl'],
            //   "description": value['title'],
            // });
            return HeroPage2(arguments: {
              "imageUrl": value['imageUrl'],
              "description": value['title'],
            });
          }));
        },
        child: Container(
            decoration: BoxDecoration(
                border: Border.all(
                    color: const Color.fromRGBO(233, 233, 233, 0.9), width: 1)),
            child: Column(
              children: <Widget>[
                Hero(
                  tag: value['title'],
                  // child: Image.asset(value['imageUrl'])),
                  child: Image.network(
                    value['imageUrl'],
                    width: 320,
                    height: 120,
                    fit: BoxFit.cover,
                  ),
                ),
                const SizedBox(height: 12),
                Text(
                  value['title'],
                  textAlign: TextAlign.center,
                  style: const TextStyle(fontSize: 20),
                )
              ],
            )),
      );
    });
    return tempList.toList();
  }

  @override
  Widget build(BuildContext context) {
    return GridView.count(
      crossAxisSpacing: 10.0,
      //水平子 Widget 之间间距
      mainAxisSpacing: 10.0,
      //垂直子 Widget 之间间距
      padding: const EdgeInsets.all(10),
      crossAxisCount: 2,
      //一行的 Widget 数量
      // childAspectRatio:0.7,
      // 宽度和高度的比例
      children: _getListData(),
    );
  }
}

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

class HeroPage2 extends StatefulWidget {
  final Map arguments;
  const HeroPage2({super.key, required this.arguments});

  @override
  State<HeroPage2> createState() => _HeroPageState();
}

class _HeroPageState extends State<HeroPage2> {
  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        Navigator.pop(context);
      },
      child: Hero(
        tag: widget.arguments["imageUrl"],
        child: Scaffold(
          backgroundColor: Colors.black,
          body: Center(
            child: AspectRatio(
              aspectRatio: 16 / 9,
              child: PhotoView(
                imageProvider: NetworkImage(widget.arguments["imageUrl"]),
              ),
            ),
          ),
        ),
      ),
    );
  }
}

7.3 配置 Hero 动画的执行时间

7.3.1 引入scheduler.dart

import 'package:flutter/scheduler.dart';

7.3.2 设置动画时间

void initState() { super.initState(); timeDilation=5.0; }

7.4 Hero +photo_view 实现微信朋友圈图片预览

7.4.1 photo_view插件支持预览图片，可放大、缩小、滑动图片

7.4.2 photo_view 官方地址：https://pub.dev/packages/photo_view

7.4.3 photo_view预览图片

1、配置依赖

photo_view: ^0.14.0

2、引入

import 'package:photo_view/photo_view.dart';

3、单张图片的预览

@override
Widget build(BuildContext context) {
    return Container(
        child: PhotoView(
            imageProvider: AssetImage("assets/large-image.jpg"),
        )
    );
}

4、多张图片的预览

引入

import 'package:photo_view/photo_view_gallery.dart'

示例

PhotoViewGallery.builder(
    itemCount: 5,
    builder: ((context, index) {
        return PhotoViewGalleryPageOptions(
    imageProvider: NetworkImage(listData[index]["imageUrl"]));
}))


PhotoViewGallery.builder(
    scrollPhysics: const BouncingScrollPhysics(),
    builder: (BuildContext context, int index) {
        return PhotoViewGalleryPageOptions(
            imageProvider:NetworkImage(widget.imageItems[index]["imageUrl"]),
        );
    },
    scrollDirection: widget.direction,
    itemCount: widget.imageItems.length,
    backgroundDecoration:
    const BoxDecoration(color: Colors.black),
    pageController: PageController(initialPage: 1),
    onPageChanged: (index) => setState(() {
    currentIndex = index;
}))

7.4.4 PhotoViewGallery.builder属性

（1）scrollPhysics

        BouncingScrollPhysics() 滑动到边界的时候有弹跳的效果

（2）scrollDirection

        Axis.horizontal 水平 、Axis.vertical垂直方向

（3）backgroundDecoration

        背景颜色

（4）builder

        builder函数 根据配置的itemCount渲染函数

（5）itemCount

        数量

（6）pageController

        PageController(initialPage: 1)

（7）onPageChanged

        onPageChanged触发的方法