校园网站建设的请示,做网站的一个黑点符号,专门做免费东西试吃的网站,自己创办网站在Flutter 中父组件调用子组件的方法可以通过GlobalKey实现#xff0c;而子组件调用父组件方法可以通过回调函数实现。
父组件
class _MyHomePageState extends StateMyHomePage {final GlobalKeyLoadPencilState loadPencilKey GlobalKeyLoadPencilSt…在Flutter 中父组件调用子组件的方法可以通过GlobalKey实现而子组件调用父组件方法可以通过回调函数实现。
父组件
class _MyHomePageState extends StateMyHomePage {final GlobalKeyLoadPencilState loadPencilKey GlobalKeyLoadPencilState();// 动画状态bool isRun false;overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(backgroundColor: Theme.of(context).colorScheme.inversePrimary,title: Text(widget.title),),body: SizedBox(width: 350,child: Column(children: [LoadPencil(backgroundColor: Colors.blue,key: loadPencilKey,changeState: (state) {setState(() {isRun state;});},),ElevatedButton(onPressed: () {if (isRun true) {loadPencilKey.currentState?.stop();} else {loadPencilKey.currentState?.start();}},child: isRun true ? const Text(停止) : const Text(开始)),],),));}
}子组件
import package:flutter/material.dart;class LoadPencil extends StatefulWidget {final Color backgroundColor;final Function(bool state) changeState;const LoadPencil({super.key, required this.backgroundColor, required this.changeState});overrideStateStatefulWidget createState() LoadPencilState();
}class LoadPencilState extends StateLoadPencilwith SingleTickerProviderStateMixin {// 定义动画控制器对象late AnimationController _controller;// 定义一个动画对象late Animation _animation;double _size 0;overridevoid initState() {super.initState();_controller AnimationController(vsync: this,duration: const Duration(seconds: 2),);final Tween tween Tween(begin: 0, end: 300);_animation tween.animate(_controller);// 监听动画帧的变化在每一帧中更新UI_animation.addListener(() {setState(() {_size _animation.value.toDouble();});});// 监听动画的状态当动画正序完成后反向执行动画_controller.addStatusListener((status) {// 动画状态status的值有dismissed动画停止在开始处、forward正向运行、reverse反向运行、completed动画停止在结束处if (status AnimationStatus.completed) {_controller.reverse();} else if (status AnimationStatus.dismissed) {_controller.forward();}});}overridevoid dispose() {super.dispose();//释放动画_controller.dispose();}overrideWidget build(BuildContext context) {return Container(width: _size,height: 2,color: widget.backgroundColor,);}// 启动start() {_controller.forward();// 向父组件通信widget.changeState(true);}// 终止stop() {_controller.stop();// 向父组件通信widget.changeState(false);}
}有一个需要注意的地方是在使用GlobalKey设置类型时这个类型子组件的State而不是子组件本身
final GlobalKeyLoadPencilState loadPencilKey GlobalKeyLoadPencilState();
