Flutter-滚动监听

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('监听'),
        ),
        body: ScrollNotificationTestRoute(),
      ),
    );
  }
}

class ScrollNotificationTestRoute extends StatefulWidget {
  @override
  _ScrollNotificationTestRouteState createState() => _ScrollNotificationTestRouteState();
}

class _ScrollNotificationTestRouteState extends State<ScrollNotificationTestRoute> {
  String _progress = "0%";

  @override
  Widget build(BuildContext context) {
    // 进度条
    return Scrollbar(
        child: NotificationListener<ScrollNotification>(
            onNotification: (ScrollNotification notification) {
              double progress = notification.metrics.pixels / notification.metrics.maxScrollExtent;
              // 重新构建
              setState(() {
                _progress = "${(progress * 100).toInt()}%";
              });
              print("BottomEdge: ${notification.metrics.extentAfter == 0}");
            },
            child: Stack(
              alignment: Alignment.center,
              children: <Widget>[
                ListView.builder(
                    itemCount: 100,
                    itemExtent: 50.0,
                    itemBuilder: (context, index) {
                      return ListTile(title: Text('$index'),);
                    }
                ),
                CircleAvatar(
                  radius: 30.0,
                  child: Text(_progress),
                  backgroundColor: Colors.black54,
                )
              ],
            )
        )
    );
  }
}