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import 'package:flutter/material.dart';import 'package:flutter_widgets/flutter_widgets.dart';void main() => runApp(new MyApp());class MyApp extends StatelessWidget {  @override  Widget build(BuildContext context) {    return new MaterialApp(      title: 'Welcome to Flutter',      theme: ThemeData(        primaryColor: Colors.red,      ),      home: MyList(),    );  }}class MyList extends StatelessWidget {  @override  Widget build(BuildContext context) {    return new Scaffold (      appBar: new AppBar(        title: new Text('Startup Name Generator'),      ),      body: _buildSuggestions(),    );  }  Widget _buildSuggestions() {    return new ListView.builder(        itemBuilder: (context, i) {          return _buildRow(i);        }    );  }  Widget _buildRow(int i) {    return SizedBox(      height: 180,      child: ListView.builder(        scrollDirection: Axis.horizontal,        itemBuilder: (_, j) {          String key = '$i - $j';          return Container(            width: 200,            height: 180,            margin: EdgeInsets.all(3.0),            decoration: BoxDecoration(                border: Border.all(width: 1)            ),            child: VisibilityDetector(              key: Key(key),              onVisibilityChanged: (visibilityInfo) {                var visiblePercentage = visibilityInfo.visibleFraction * 100;                debugPrint('Widget ${visibilityInfo.key} is ${visiblePercentage.toInt()}% visible');              },              child: Center(                child: Text(key, style: TextStyle(fontSize: 18.0)),              ),            ),          );        },      ),    );  }}https://pub.dev/packages/flutter_widgets写了个 ListView 监听可见内容的Demo, 可以参考下. 用的是 flutter_widgets库提供的 VisibilityDetector

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