Flutter ScrollController滚动监听及控制示例详解

ScrollController({
  double initialScrollOffset = 0.0, //初始滚动位置
  this.keepScrollOffset = true,//是否保存滚动位置
  ...
})

controller.addListener(()=>print(controller.offset))

import 'package:demo202112/utils/common_appbar.dart';
import 'package:flutter/material.dart';
/// @Author wywinstonwy
/// @Date 2022/1/19 10:46 下午
/// @Description:
class MyScrollController extends StatefulWidget {
  const MyScrollController({Key? key}) : super(key: key);
  @override
  _MyScrollControllerState createState() => _MyScrollControllerState();
}
class _MyScrollControllerState extends State<MyScrollController> {
  final ScrollController _controller = ScrollController();
  bool showToTopBtn = false; //是否显示“返回到顶部”按钮
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    //监听滚动事件，打印滚动位置
    _controller.addListener(() {
      //打印滚动位置
      print(_controller.offset);
      if (_controller.offset < 1000 && showToTopBtn) {
        setState(() {
          showToTopBtn = false;
        });
      } else if (_controller.offset >= 1000 && showToTopBtn == false) {
        setState(() {
          showToTopBtn = true;
        });
      }
    });
  }
  @override
  void dispose() {
    //为了避免内存泄露，需要调用_controller.dispose
    _controller.dispose();
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: getAppBar('滚动监听以及控制'),
      body: _buildScollbar(),
      floatingActionButton: showToTopBtn==false?null:FloatingActionButton(
        onPressed: (){
          //返回到顶部时候执行动画
          _controller.animateTo(0, duration: const Duration(milliseconds: 200), curve: Curves.easeIn);
        },
        child: const Icon(Icons.arrow_upward),),
    );
  }
  _buildScollbar(){
    return Scrollbar(
        child: ListView.builder(
          controller: _controller,
            itemCount: 100,
            itemExtent: 44,
            itemBuilder: (context,index){
          return ListTile(title: Text('$index'),);
        })
    );
  }
}

ListView(key: PageStorageKey(1), ... );
...
ListView(key: PageStorageKey(2), ... );

double get offset => position.pixels;

...
controller.positions.elementAt(0).pixels
controller.positions.elementAt(1).pixels
...    

ScrollPosition createScrollPosition(
    ScrollPhysics physics,
    ScrollContext context,
    ScrollPosition oldPosition);
void attach(ScrollPosition position) ;
void detach(ScrollPosition position) ;

import 'package:demo202112/utils/common_appbar.dart';
import 'package:flutter/material.dart';
/// @Author wywinstonwy
/// @Date 2022/1/19 11:21 下午
/// @Description: 
class MyScrollcontroller2 extends StatefulWidget {
  const MyScrollcontroller2({Key? key}) : super(key: key);
  @override
  _MyScrollcontroller2State createState() => _MyScrollcontroller2State();
}
class _MyScrollcontroller2State extends State<MyScrollcontroller2> {
  String _progress ='0%';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: getAppBar("滚动监听"),
      body: NotificationListener<ScrollNotification>(
        onNotification: (ScrollNotification notification){
          double progress = notification.metrics.pixels/notification.metrics.maxScrollExtent;
          //重新构建
          setState(() {
            _progress ='${(progress*100).toInt()}%';
          });
          print("BottomEdge: ${notification.metrics.extentAfter == 0}");
          return false;          //return true; //放开此行注释后，进度条将失效
        },
        child: Stack(
          alignment: Alignment.center,
          children: [
            ListView.builder(
              itemCount: 100,
                itemExtent: 50,
                itemBuilder: (context,index){
                return ListTile(title: Text('$index'),);
                }),
            CircleAvatar(
              radius: 30,
              child: Text(_progress),
              backgroundColor: Colors.black54,
            )
          ],
        ),
      ),
    );
  }
}