该项目无法识别 AsyncSnapshot
The project not recognize AsyncSnapshot
我正在尝试从 json link 获取数据，但是当我 运行 应用程序时我没有看到任何东西，我认为问题出在 AsyncSnapshot 因为项目无法定义此 class 尽管所有导入在主文件中都是正确的并且 pubspec.yaml 依赖项没问题
我看到了类似的 并尝试了解决方案，但它对我也不起作用
这是完整的代码
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("http://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
print(users.length);
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Column(
children: [
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
return ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
);
},
),
],
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}
pubspec.yaml
name: yat_flutter_app
description: A new Flutter application.
# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev
# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1
environment:
sdk: ">=2.7.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
http: ^0.12.2
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^1.0.0
dev_dependencies:
flutter_test:
sdk: flutter
# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec
# The following section is specific to Flutter.
flutter:
# The following line ensures that the Material Icons font is
# included with your application, so that you can use the icons in
# the material Icons class.
uses-material-design: true
# To add assets to your application, add an assets section, like this:
# assets:
# - images/a_dot_burr.jpeg
# - images/a_dot_ham.jpeg
# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.dev/assets-and-images/#resolution-aware.
# For details regarding adding assets from package dependencies, see
# https://flutter.dev/assets-and-images/#from-packages
# To add custom fonts to your application, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts from package dependencies,
# see https://flutter.dev/custom-fonts/#from-packages
我发现代码主要有两点。
第一个是关于FutureBuilder的使用。您需要等到 asyncSnapshop 有数据后再尝试使用它。您实际上需要询问是否 asyncSnapshop.hasData（检查答案末尾的代码）。
第二件事有点奇怪。如果请求是通过 http 完成的，json-generator.com 不会 return 应用上下文中的任何数据。一旦我使用 https.
，它就开始 returning 数据
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("https://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Column(
children: [
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
if(asyncSnapshop.hasData) {
return Expanded(
child: ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
),
);
} else {
return Text("Loading, please wait...");
}
},
),
],
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}
只需将正文中的 Column 替换为 Container，您的代码就可以工作了
我认为 FutureBuilder 不会与 Column 一起执行，这很奇怪，这很奇怪，它应该适用于两个小部件
编辑后的完整代码
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("https://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
print(users.length);
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Container(
child:
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
return ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
);
},
),
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}
我正在尝试从 json link 获取数据，但是当我 运行 应用程序时我没有看到任何东西，我认为问题出在 AsyncSnapshot 因为项目无法定义此 class 尽管所有导入在主文件中都是正确的并且 pubspec.yaml 依赖项没问题
我看到了类似的
这是完整的代码
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("http://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
print(users.length);
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Column(
children: [
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
return ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
);
},
),
],
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}
pubspec.yaml
name: yat_flutter_app
description: A new Flutter application.
# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev
# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1
environment:
sdk: ">=2.7.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
http: ^0.12.2
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^1.0.0
dev_dependencies:
flutter_test:
sdk: flutter
# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec
# The following section is specific to Flutter.
flutter:
# The following line ensures that the Material Icons font is
# included with your application, so that you can use the icons in
# the material Icons class.
uses-material-design: true
# To add assets to your application, add an assets section, like this:
# assets:
# - images/a_dot_burr.jpeg
# - images/a_dot_ham.jpeg
# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.dev/assets-and-images/#resolution-aware.
# For details regarding adding assets from package dependencies, see
# https://flutter.dev/assets-and-images/#from-packages
# To add custom fonts to your application, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts from package dependencies,
# see https://flutter.dev/custom-fonts/#from-packages
我发现代码主要有两点。
第一个是关于FutureBuilder的使用。您需要等到 asyncSnapshop 有数据后再尝试使用它。您实际上需要询问是否 asyncSnapshop.hasData（检查答案末尾的代码）。
第二件事有点奇怪。如果请求是通过 http 完成的，json-generator.com 不会 return 应用上下文中的任何数据。一旦我使用 https.
，它就开始 returning 数据import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("https://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Column(
children: [
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
if(asyncSnapshop.hasData) {
return Expanded(
child: ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
),
);
} else {
return Text("Loading, please wait...");
}
},
),
],
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}
只需将正文中的 Column 替换为 Container，您的代码就可以工作了
我认为 FutureBuilder 不会与 Column 一起执行，这很奇怪，这很奇怪，它应该适用于两个小部件
编辑后的完整代码
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
void main() {
runApp(MaterialApp(
home: MyApp()));
}
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
Future<List<User>> _getUsers() async {
var data = await http.get("https://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
var jasonData = json.decode(data.body);
List<User> users = [];
for(var i in jasonData){
User user = User(i["index"], i["about"], i["name"], i["picture"], i["company"], i["email"]);
users.add(user);
}
print(users.length);
return users;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Yat Flutter App',
style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold, fontFamily: 'Tahoma') ),
),
body: Container(
child:
FutureBuilder(
future: _getUsers(),
builder: (BuildContext context,AsyncSnapshot asyncSnapshop){
return ListView.builder(
itemCount: asyncSnapshop.data.length,
itemBuilder: (BuildContext context, int index){
return ListTile(
title: Text(asyncSnapshop.data[index].name),
);
}
);
},
),
),
);
}
}
class User{
final int index;
final String about;
final String name;
final String picture;
final String company;
final String email;
User(this.index, this.about, this.name, this.picture, this.company,
this.email);
}