我刚开始学习Flutter . 我遇到了一个很大的问题,那就是在复杂的列表中滚动不好 . 假设我们的ListView中有5种不同的项目类型,某些项目类型必须显示图像,并且它是无限滚动 . 我阅读了很多关于ListView for Flutter的文章和帖子,我看到的所有内容都是带有文本的简单列表 . 如何进行平滑滚动?
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Startup Name Generator',
home: new RandomWords(),
);
}
}
class RandomWords extends StatefulWidget {
@override
RandomWordsState createState() => new RandomWordsState();
}
class RandomWordsState extends State<RandomWords> {
final List<WordPair> _suggestions = <WordPair>[];
final TextStyle _biggerFont = const TextStyle(fontSize: 18.0);
List<int> items = List.generate(10, (i) => i);
ScrollController _scrollController = new ScrollController();
bool isPerformingRequest = false;
@override
void initState() {
super.initState();
_scrollController.addListener(() {
if (_scrollController.position.pixels ==
_scrollController.position.maxScrollExtent) {
_getMoreData();
}
});
}
@override
void dispose() {
_scrollController.dispose();
super.dispose();
}
_getMoreData() async {
if (!isPerformingRequest) {
setState(() => isPerformingRequest = true);
List<int> newEntries = await fakeRequest(
items.length, items.length + 10); //returns empty list
if (newEntries.isEmpty) {
double edge = 50.0;
double offsetFromBottom = _scrollController.position.maxScrollExtent -
_scrollController.position.pixels;
if (offsetFromBottom < edge) {
_scrollController.animateTo(
_scrollController.offset - (edge - offsetFromBottom),
duration: new Duration(milliseconds: 500),
curve: Curves.easeOut);
}
}
setState(() {
items.addAll(newEntries);
isPerformingRequest = false;
});
}
}
Future<List<int>> fakeRequest(int from, int to) async {
return Future.delayed(Duration(seconds: 1), () {
return List.generate(to - from, (i) => i + from);
});
}
Widget _buildProgressIndicator() {
return new Padding(
padding: const EdgeInsets.all(8.0),
child: new Center(
child: new Opacity(
opacity: isPerformingRequest ? 1.0 : 0.0,
child: new CircularProgressIndicator(),
),
),
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: AppBar(
title: Text(""),
),
body: ListView.builder(
itemCount: items.length + 1,
itemBuilder: (context, index) {
if (index == items.length) {
return _buildProgressIndicator();
} else {
if (index % 5 == 0) {
return Image.network(
"http://sanctum-inle-resort.com/wp-content/uploads/2015/11/Sanctum_Inl_Resort_Myanmar_Flowers_Frangipani.jpg",
height: 200.0,
);
} else if (index.isOdd) {
return Container(
padding: EdgeInsets.all(16.0),
child: ListTile(
leading: Icon(Icons.person),
title: Text('This is title'),
),
);
} else {
return ListTile(title: new Text("Number $index"));
}
}
},
controller: _scrollController,
),
);
}
}
1 回答
我认为问题在于,当用户已经到列表末尾并且没有更多项目然后它正在执行加载数据的虚假请求时请求数据异步,但这需要一秒钟,这就是为什么它是studdering
这将获得滚动列表的结束,因此它在用户位于列表末尾的位置开始加载,您可以使用偏移量更改此值,以便更早地开始加载
要测试这个,您可以尝试更改:
至:
和
至: