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Flutter Hero动画开发实用教程

2019.04.17 23:44 1422浏览

Flutter 动画开发实用教程

在这篇文章中,将向大家分享Flutter动画中的重要一员Hero动画,以及一些Hero动画的开发技巧和经验

  • 在大家Flutter开发环境过程中遇到无法解决的问题可以在课程问答区进行提问,课程老师会对你进行辅导和帮助;

精心设计的动画会让用户界面感觉更直观、流畅,能改善用户体验。 Flutter的动画支持可以轻松实现各种动画类型。许多widget,特别是Material Design widgets, 都带有在其设计规范中定义的标准动画效果,但也可以自定义这些效果,在开始学习之前呢,我们先来快速过一下本篇文章的目录:

目录

  • 什么是Hero动画?
  • 如何实现标准Hero动画?
  • Hero的函数原型的函数原型是什么?
  • 如何实现径向Hero动画?

什么是Hero动画?

在 Flutter中可以用 Herowidget创建这个动画。当 Hero通过动画从源页面飞到目标页面时,目标页面逐渐淡入视野。通常, Hero是用户界面的一小部分,如图片,它通常在两个页面都有。从用户的角度来看, Hero在页面之间“飞翔”。接下来我们一起来学习如何创建Hero动画:

实现标准Hero动画

Standard-Hero-Animation

...
class PhotoHero extends StatelessWidget {
  const PhotoHero({ Key key, this.photo, this.onTap, this.width }) : super(key: key);

  final String photo;
  final VoidCallback onTap;
  final double width;

  Widget build(BuildContext context) {
    return SizedBox(
      width: width,
      child: Hero(
        tag: photo,
        child: Material(
          color: Colors.transparent,
          child: InkWell(
            onTap: onTap,
            child: Image.network(
              photo,
              fit: BoxFit.contain,
            ),
          ),
        ),
      ),
    );
  }
}

class HeroAnimation extends StatelessWidget {
  Widget build(BuildContext context) {
    timeDilation = 10.0; // 1.0 means normal animation speed.

    return Scaffold(
      appBar: AppBar(
        title: const Text('Basic Hero Animation'),
      ),
      body: Center(
        child: PhotoHero(
          photo: 'https://raw.githubusercontent.com/flutter/website/master/examples/_animation/Hero_animation/images/flippers-alpha.png',
          width: 300.0,
          onTap: () {
            Navigator.of(context).push(MaterialPageRoute<void>(
                builder: (BuildContext context) {
                  return Scaffold(
                    appBar: AppBar(
                      title: const Text('Flippers Page'),
                    ),
                    body: Container(
                      // Set background to blue to emphasize that it's a new route.
                      color: Colors.lightBlueAccent,
                      padding: const EdgeInsets.all(16.0),
                      alignment: Alignment.topLeft,
                      child: PhotoHero(
                        photo: 'https://raw.githubusercontent.com/flutter/website/master/examples/_animation/Hero_animation/images/flippers-alpha.png',
                        width: 100.0,
                        onTap: () {
                          Navigator.of(context).pop();
                        },
                      ),
                    ),
                  );
                }
            ));
          },
        ),
      ),
    );
  }
}
...

Hero的函数原型

 const Hero({
    Key key,
     this.tag,
    this.createRectTween,
    this.flightShuttleBuilder,
    this.placeholderBuilder,
    this.transitionOnUserGestures = false,
     this.child,
  }) : assert(tag != null),
       assert(transitionOnUserGestures != null),
       assert(child != null),
       super(key: key);
  • tag]:[必须]用于关联两个Hero动画的标识;
  • createRectTween:[可选]定义目标Hero的边界,在从起始位置到目的位置的“飞行”过程中该如何变化;
  • child:[必须]定义动画所呈现的widget;

实现径向Hero动画

Radial-Hero-Animation

...

class RadialExpansionDemo extends StatelessWidget {
  static const double kMinRadius = 32.0;
  static const double kMaxRadius = 128.0;
  static const opacityCurve = const Interval(0.0, 0.75, curve: Curves.fastOutSlowIn);

  static RectTween _createRectTween(Rect begin, Rect end) {
    return MaterialRectCenterArcTween(begin: begin, end: end);
  }

  static Widget _buildPage(BuildContext context, String imageName, String description) {
    return Container(
      color: Theme.of(context).canvasColor,
      child: Center(
        child: Card(
          elevation: 8.0,
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              SizedBox(
                width: kMaxRadius * 2.0,
                height: kMaxRadius * 2.0,
                child: Hero(
                  createRectTween: _createRectTween,
                  tag: imageName,
                  child: RadialExpansion(
                    maxRadius: kMaxRadius,
                    child: Photo(
                      photo: imageName,
                      onTap: () {
                        Navigator.of(context).pop();
                      },
                    ),
                  ),
                ),
              ),
              Text(
                description,
                style: TextStyle(fontWeight: FontWeight.bold),
                textScaleFactor: 3.0,
              ),
              const SizedBox(height: 16.0),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildHero(BuildContext context, String imageName, String description) {
    return Container(
      width: kMinRadius * 2.0,
      height: kMinRadius * 2.0,
      child: Hero(
        createRectTween: _createRectTween,
        tag: imageName,
        child: RadialExpansion(
          maxRadius: kMaxRadius,
          child: Photo(
            photo: imageName,
            onTap: () {
              Navigator.of(context).push(
                PageRouteBuilder<void>(
                  pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
                    return AnimatedBuilder(
                        animation: animation,
                        builder: (BuildContext context, Widget child) {
                          return Opacity(
                            opacity: opacityCurve.transform(animation.value),
                            child: _buildPage(context, imageName, description),
                          );
                        }
                    );
                  },
                ),
              );
            },
          ),
        ),
      ),
    );
  }

  
  Widget build(BuildContext context) {
    timeDilation = 5.0; // 1.0 is normal animation speed.

    return Scaffold(
      appBar: AppBar(
        title: const Text('Radial Transition Demo'),
      ),
      body: Container(
        padding: const EdgeInsets.all(32.0),
        alignment: FractionalOffset.bottomLeft,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            _buildHero(context, 'https://raw.githubusercontent.com/flutter/website/master/examples/_animation/radial_Hero_animation/images/chair-alpha.png', 'Chair'),
            _buildHero(context, 'https://raw.githubusercontent.com/flutter/website/master/examples/_animation/radial_Hero_animation/images/binoculars-alpha.png', 'Binoculars'),
            _buildHero(context, 'https://raw.githubusercontent.com/flutter/website/master/examples/_animation/radial_Hero_animation/images/beachball-alpha.png', 'Beach ball'),
          ],
        ),
      ),
    );
  }
}
...
  • 本节学习过程中遇到无法解决的问题可以在课程问答区进行提问,课程老师会对你进行辅导和帮助;
  • 欢迎加入课程官方群:795410523 和讲师以及其他师兄弟们一起学习交流;
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