flutter中使用缓存

前言

在flutter项目中使用ListView或者PageView等有滚动条组件的时候，切换页面的时候，再切换回来会丢失之前的滑动状态，这个时候就需要需要使用缓存功能

缓存类

import 'package:flutter/material.dart';

class KeepAliveWrapper extends StatefulWidget {
 const KeepAliveWrapper(
     {Key? key, @required this.child, this.keepAlive = true})
     : super(key: key);

 final Widget? child;
 final bool keepAlive;

 @override
 State<KeepAliveWrapper> createState() => _KeepAliveWrapperState();
}

class _KeepAliveWrapperState extends State<KeepAliveWrapper>
   with AutomaticKeepAliveClientMixin {
 @override
 Widget build(BuildContext context) {
   return widget.child!;
 }

 @override
 bool get wantKeepAlive => widget.keepAlive;  
}

使用

在需要缓存的组件使用KeepAliveWrapper包裹一下即可

@override
  Widget build(BuildContext context) {
    return KeepAliveWrapper(
        child: Scaffold(
      body: Stack(
        children: [_homePage(), _appBar()],
      ),
    ));
  }