flutter使用AnimatedBuilder动画不播放

解决方案:将AnimatedBuilder包裹在如Center的布局约束中

关键代码:

class GrowTransition extends StatelessWidget {
  GrowTransition({required this.child, required this.animation});

  late final Widget child;
  late final Animation<double> animation;

  @override
  Widget build(BuildContext context) => Center(
        child: AnimatedBuilder(
          animation: animation,
          builder: (context, child) => Container(
            child: child,
            height: animation.value,
            width: (animation).value,
          ),
          child: child,
        ),
      );
}

完整代码:

import 'package:flutter/material.dart';

///这是一个使用AnimatedBuilder拆分动画的,实现动画和widget进行分离的实例
class AniBuilder extends StatefulWidget {
  @override
  _AniBuilder createState() => _AniBuilder();
}

class _AniBuilder extends State<AniBuilder>
    with SingleTickerProviderStateMixin {
  Animation<double>? animation;
  AnimationController? controller;

  @override
  void initState() {
    super.initState();
    controller =
        AnimationController(vsync: this, duration: Duration(seconds: 2));
    animation = Tween<double>(begin: 0, end: 300).animate(controller!);
    controller!.forward();
  }

  @override
  Widget build(BuildContext context) {
    Widget aniPlayerContainer = AniBuilderWidget().build(context);

    ///这种写法将AniBuilderWidget与GrowTransition分离,
    ///GrowTransition用于动画的播放的设置
    ///AniBuilderWidget用于设定播发动画的组件
    return new GrowTransition(
        child: Container(child: (aniPlayerContainer as Container).child),
        animation: (animation as Animation<double>));
  }

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

class AniBuilderWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: FlutterLogo(),
    );
  }
}

class GrowTransition extends StatelessWidget {
  GrowTransition({required this.child, required this.animation});

  late final Widget child;
  late final Animation<double> animation;

  @override
  Widget build(BuildContext context) => Center(
        child: AnimatedBuilder(
          animation: animation,
          builder: (context, child) => Container(
            child: child,
            height: animation.value,
            width: (animation).value,
          ),
          child: child,
        ),
      );
}

参考链接:

1. https://flutterchina.club/layout/

2. https://blog.csdn.net/ShuSheng0007/article/details/110292757

3. https://coding.imooc.com/learn/questiondetail/pylDvPyAVlgPkBNm.html