Flutter 未来字符串作为CachedNetworkImage的URL
CachedNetworkImage是否有一种方法可以将Flutter 未来字符串作为CachedNetworkImage的URL,flutter,dart,Flutter,Dart,CachedNetworkImage是否有一种方法可以将未来接受为图像URL 我试图显示存储在Firebase存储中的用户配置文件图片,但由于图片可能会更改,下载URL也会更改 我知道如何获取下载URL,但到目前为止,我只在FutureBuilder中使用了它。有什么建议可以让我的async等待URL吗 或者有没有一种方法可以将URL存储在应用程序本身中?您可以在下面复制粘贴运行完整代码 步骤1:您可以将下载URL逻辑放入getUrl(),我使用3秒延迟来模拟 Future<String&
未来
接受为图像URL
我试图显示存储在Firebase存储中的用户配置文件图片,但由于图片可能会更改,下载URL也会更改
我知道如何获取下载URL,但到目前为止,我只在FutureBuilder
中使用了它。有什么建议可以让我的async
等待URL吗
或者有没有一种方法可以将URL存储在应用程序本身中?您可以在下面复制粘贴运行完整代码
步骤1:您可以将下载URL逻辑放入
getUrl()
,我使用3秒延迟来模拟Future<String> getUrl() async {
await Future.delayed(Duration(seconds: 3), () {});
return Future.value("https://via.placeholder.com/350x150");
}
工作演示
完整代码
import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<String> _future;
Future<String> getUrl() async {
await Future.delayed(Duration(seconds: 3), () {});
return Future.value("https://via.placeholder.com/350x150");
}
@override
void initState() {
_future = getUrl();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<String> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('none');
case ConnectionState.waiting:
return Center(
child: Column(
children: [
Text("Future builder"),
CircularProgressIndicator(),
],
));
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return Center(
child: CachedNetworkImage(
imageUrl: snapshot.data,
placeholder: (context, url) => Column(
children: [
Text("CachedNetworkImage"),
CircularProgressIndicator(),
],
),
errorWidget: (context, url, error) => Icon(Icons.error),
),
);
}
}
}));
}
}
import'package:cached_network_image/cached_network_image.dart';
进口“包装:颤振/材料.省道”;
void main(){
runApp(MyApp());
}
类MyApp扩展了无状态小部件{
@凌驾
小部件构建(构建上下文){
返回材料PP(
标题:“颤振演示”,
主题:主题数据(
主样本:颜色。蓝色,
视觉密度:视觉密度。自适应平台密度,
),
主页:MyHomePage(标题:“颤振演示主页”),
);
}
}
类MyHomePage扩展StatefulWidget{
MyHomePage({Key,this.title}):超级(Key:Key);
最后的字符串标题;
@凌驾
_MyHomePageState createState()=>\u MyHomePageState();
}
类_MyHomePageState扩展状态{
未来,未来;;
Future getUrl()异步{
等待未来。延迟(持续时间(秒:3),({});
返回Future.value(“https://via.placeholder.com/350x150");
}
@凌驾
void initState(){
_future=getUrl();
super.initState();
}
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
标题:文本(widget.title),
),
正文:未来建设者(
未来:未来,
生成器:(上下文,异步快照){
交换机(快照.连接状态){
案例连接状态。无:
返回文本(“无”);
案例连接状态。正在等待:
返回中心(
子:列(
儿童:[
文本(“未来建设者”),
CircularProgressIndicator(),
],
));
案例连接状态.active:
返回文本(“”);
案例连接状态。完成:
if(snapshot.hasError){
返回文本(
“${snapshot.error}”,
样式:TextStyle(颜色:Colors.red),
);
}否则{
返回中心(
子:CachedNetworkImage(
imageUrl:snapshot.data,
占位符:(上下文,url)=>列(
儿童:[
文本(“CachedNetworkImage”),
CircularProgressIndicator(),
],
),
errorWidget:(上下文、url、错误)=>图标(Icons.error),
),
);
}
}
}));
}
}
import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<String> _future;
Future<String> getUrl() async {
await Future.delayed(Duration(seconds: 3), () {});
return Future.value("https://via.placeholder.com/350x150");
}
@override
void initState() {
_future = getUrl();
super.initState();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder(
future: _future,
builder: (context, AsyncSnapshot<String> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('none');
case ConnectionState.waiting:
return Center(
child: Column(
children: [
Text("Future builder"),
CircularProgressIndicator(),
],
));
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return Center(
child: CachedNetworkImage(
imageUrl: snapshot.data,
placeholder: (context, url) => Column(
children: [
Text("CachedNetworkImage"),
CircularProgressIndicator(),
],
),
errorWidget: (context, url, error) => Icon(Icons.error),
),
);
}
}
}));
}
}