从本质上讲,我想做this,但不是更新单个图像,而是更新图像列表。我有一个基于图像URL的List<String>
图像的ListView
。如下所示:
import 'package:flutter/material.dart';
import 'package:cached_network_image/cached_network_image.dart';
void main() => runApp(new MyApp());
class MyApp extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new MyAppState();
}
}
class MyAppState extends State<MyApp> {
double padding = 5.0;
String one = 'https://SOME_URL_HERE.com';
String two = 'https://SOME_URL_HERE.com';
String three = 'https://SOME_URL_HERE.com';
String four = 'https://SOME_URL_HERE.com';
List urls;
@override
Widget build(BuildContext context) {
urls = List();
urls.add(one);
urls.add(two);
return new MaterialApp(
debugShowCheckedModeBanner: false,
home: new Scaffold(
appBar: new AppBar(
title: new Text("Image list test"),
),
body: showBody(),
),
);
}
Widget showBody() {
return Padding(
padding: EdgeInsets.only(top: 15.0, left: 10.0, right: 10.0),
child: ListView(
children: <Widget>[
showItemImages(),
RaisedButton(
child: Text("Change image"),
onPressed: () {
setState(() {
urls = List();
urls.add(three);
urls.add(four);
});
},
),
Container(
child: Text('urls length: ${urls.length}'),
),
],
),
);
}
Widget showItemImages() {
return Padding(
padding: EdgeInsets.all(padding),
child: Container(
margin: EdgeInsets.symmetric(vertical: 20.0),
height: 200,
child: urls.length > 0 //item.images.length > 0
? getImagesListView(context)
: Container(child: Text('No images yet'))),
);
}
getImagesListView(BuildContext context) {
return ListView.builder(
shrinkWrap: true,
scrollDirection: Axis.horizontal,
itemCount: urls.length,
itemBuilder: (BuildContext context, int index) {
return new Container(
width: 160.0,
child: _sizedContainer(
new CachedNetworkImage(
key: new ValueKey<String>(urls[index]),
imageUrl: urls[index],
//placeholder: (context, url) => new CircularProgressIndicator(),
),
),
);
},
);
}
Widget _sizedContainer(Widget child) {
return new SizedBox(
width: 300.0,
height: 150.0,
child: new Center(
child: child,
),
);
}
}
当我按下按钮时,它应该清除列表并向其中添加两个新元素,但它不起作用
发布于 2019-04-01 00:22:53
下面3行代码:
urls = List();
urls.add(one);
urls.add(two);
是否应该将而不是放入@override
小部件构建方法中。将它们放在那里意味着您每次设置状态时都要重新初始化urls,您应该将这些行放入@override initState()
方法中。
https://stackoverflow.com/questions/55442814
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