Flutter实现心动的动画特效

2024-04-02 19:04:59 354人浏览薄情痞子

摘要

目录实现动画混入 SingleTickerProviderStateMixin创建动画抽离成小组件完整代码为了追求更好的用户体验，有时候我们需要一个类似心跳一样跳动着的控件来吸引用户

实现动画

混入 SingleTickerProviderStateMixin

当创建一个 AnimationController 时，需要传递一个vsync参数，存在vsync时会防止动画的UI不在当前屏幕时消耗不必要的资源。通过混入 SingleTickerProviderStateMixin 。

class _MyHomePageState extends State<MyHomePage>  with SingleTickerProviderStateMixin{}

创建动画

创建一个间隔将近一秒钟的动画控制器：

  late final AnimationController animController;

  @override
  void initState() {
    super.initState();
    animController = AnimationController(
      duration: const Duration(milliseconds: 800),
      vsync: this,
    );
    }

心跳动画是从小变大，再变小，所以需要一个值大小变化的动画：

  late final Animation<double> animation;

  @override
  void initState() {
    super.initState();
    animController = AnimationController(
      duration: const Duration(milliseconds: 800),
      vsync: this,
    );
     animation = Tween<double>(
      begin: 0.9,
      end: 1.05,
    );
    }

心跳是不间断的，所以需要监听动画完成时恢复动画，再继续开始动画：

    animation = Tween<double>(
      begin: 0.9,
      end: 1.05,
    ).animate(animController)
      ..addListener(() {
        setState(() {});
      })
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed) {
          animController.reverse();
        } else if (status == AnimationStatus.dismissed) {
          animController.forward();
        }
      });

使用缩放控件：

TransfORM.scale(
                scale: animation.value,
                child: const FlutterLoGo(
                  size: 80,
                ),
              ),

为了跳动效果，突出跳动动画，把缩回去的时间改短：

   animController = AnimationController(
      reverseDuration: const Duration(milliseconds: 700),
      duration: const Duration(milliseconds: 800),
      vsync: this,
    );

最后别忘了释放资源：

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

抽离成小组件

为了每次用到类似的动画只需引入即可，需要分离动画和显示的组件。新建一个BounceWidget，包含动画，然后可以传入UI组件：

class BounceWidget extends StatefulWidget {
  final Widget child;

  const BounceWidget({
    Key? key,
    required this.child,
  }) : super(key: key);

  @override
  State<BounceWidget> createState() => _BounceWidgetState();
}

继续实现动画：

class _BounceWidgetState extends State<BounceWidget>
    with SingleTickerProviderStateMixin {
  late Animation<double> animation;
  late AnimationController animController;

  @override
  void initState() {
    super.initState();
    animController = AnimationController(
      reverseDuration: const Duration(milliseconds: 700),
      duration: const Duration(milliseconds: 800),
      vsync: this,
    );
    animation = Tween<double>(
      begin: 0.9,
      end: 1.05,
    ).animate(animController)
      ..addListener(() {
        setState(() {});
      })
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed) {
          animController.reverse();
        } else if (status == AnimationStatus.dismissed) {
          animController.forward();
        }
      });
    animController.forward();
  }

  @override
  Widget build(BuildContext context) {
    return Transform.scale(
      scale: animation.value,
      child: widget.child,
    );
  }

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

去引入动画：

  Center(
              child: BounceWidget(
                child: FlutterLogo(
                  size: 80,
                ),
              ),

完整代码

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: 'Flutter Demo Home Page'),
    );
  }
}

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> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
        padding: const EdgeInsets.only(top: 80, left: 16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: const <Widget>[
            Text(
              "心动的",
              style: TextStyle(
                fontSize: 28,
                color: Colors.black,
              ),
            ),
            Text(
              "感觉",
              style: TextStyle(
                fontSize: 48,
                color: Colors.black,
              ),
            ),
            Center(
              child: BounceWidget(
                child: FlutterLogo(
                  size: 80,
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

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