我正在尝试使用API在Flutter上加载博客。由于某些原因，文件未加载到模拟器上，并且代码未显示任何错误或建议。一旦我单击运行，在连接后，它会突然停止...请，如果有人可以预览代码并帮助我。.错误日志中说了一些关于不可变的内容，我没有真正遵循。
Main.dart
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'package:html/parser.dart';
import 'pages/post_view.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var _isLoading = true; //For progress bar
var posts;
var imgUrl;
//initialization
void initState() {
super.initState();
_fetchData();
}
//Function to fetch data from JSON
_fetchData() async {
print("attempting");
final url =
"https://www.googleapis.com/blogger/v3/blogs/MY BLOG ID HERE/posts/?key= API KEY HERE";
final response = await http.get(url);
print(response);
if (response.statusCode == 200) {
//HTTP OK is 200
final Map items = json.decode(response.body);
var post = items['items'];
setState(() {
_isLoading = false;
this.posts = post;
});
}
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Blogger"),
actions: <Widget>[
new IconButton(
icon: new Icon(Icons.refresh),
onPressed: () {
setState(() {
_isLoading = true;
});
_fetchData();
})
],
),
body: new Center(
child: _isLoading
? new CircularProgressIndicator()
: new ListView.builder(
itemCount: this.posts != null ? this.posts.length : 0,
itemBuilder: (context, i) {
final Post = this.posts[i];
final postDesc = Post["content"];
//All the below code is to fetch the image
var document = parse(postDesc);
//Regular expression
RegExp regExp = new RegExp(
r"(https?:\/\/.*\.(?:png|jpg|gif))",
caseSensitive: false,
multiLine: false,
);
final match = regExp
.stringMatch(document.outerHtml.toString())
.toString();
//print(document.outerHtml);
//print("firstMatch : " + match);
//Converting the regex output to image (Slashing) , since the output from regex was not perfect for me
if (match.length > 5) {
if (match.contains(".jpg")) {
imgUrl = match.substring(0, match.indexOf(".jpg"));
print(imgUrl);
} else {
imgUrl =
"https://pbs.twimg.com/profile_images/916384996092448768/PF1TSFOE_400x400.jpg";
}
}
String description = document.body.text.trim();
//print(description);
return new Container(
padding:
const EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 8.0),
child: new Column(
mainAxisAlignment: MainAxisAlignment.spaceAround,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Container(
width: 500.0,
height: 180.0,
decoration: new BoxDecoration(
shape: BoxShape.rectangle,
image: new DecorationImage(
fit: BoxFit.fill,
//check if the image is not null (length > 5) only then check imgUrl else display default img
image: new NetworkImage(imgUrl
.toString()
.length >
10
? imgUrl.toString()
: "https://pbs.twimg.com/profile_images/916384996092448768/PF1TSFOE_400x400.jpg")),
),
),
new Padding(
padding:
const EdgeInsets.symmetric(vertical: 10.0),
child: new Text(
Post["title"],
maxLines: 3,
style: new TextStyle(
fontSize: 18.0,
fontWeight: FontWeight.bold,
),
),
),
new Text(
description.replaceAll("\n", ", "),
maxLines: 2,
overflow: TextOverflow.ellipsis,
style: new TextStyle(fontSize: 15.0),
),
new Padding(
padding:
const EdgeInsets.symmetric(vertical: 16.0),
child: new RaisedButton(
child: new Text("READ MORE",style: new TextStyle(color: Colors.white),),
color: Colors.blue,
onPressed: () {
//We will pass description to postview through an argument
Navigator
.of(context)
.push(new MaterialPageRoute<Null>(
builder: (BuildContext context) {
return PostView(Post['title'],description,imgUrl);
},
));
},
),
),
Divider(),
],
),
);
},
)));
}
}
Post_view.dart
import 'package:flutter/material.dart';
class PostView extends StatelessWidget {
var desc, title, image;
PostView(String title, String desc, String image) {
this.desc = desc;
this.title = title;
this.image = image;
}
@override
Widget build(BuildContext context) {
if (desc.toString().contains("\n\n\n\n")) {
desc = desc.toString().replaceAll("\n\n\n\n", "\n\n");
}
if (desc.toString().contains("\n\n\n")) {
desc = desc.toString().replaceAll("\n\n\n", "\n");
}
return new Scaffold(
appBar: new AppBar(
title: new Text("Blogger"),
),
body: new Container(
child: new SingleChildScrollView(
child: new Column(
children: <Widget>[
new Padding(
padding:
const EdgeInsets.symmetric(vertical: 16.0, horizontal: 16.0),
child: new Text(
title,
style: new TextStyle(
fontSize: 22.0,
fontWeight: FontWeight.bold,
),
),
),
new Padding(
padding:
const EdgeInsets.symmetric(vertical: 16.0, horizontal: 16.0),
child: new Container(
width: 500.0,
height: 180.0,
decoration: new BoxDecoration(
shape: BoxShape.rectangle,
image: new DecorationImage(
fit: BoxFit.fill,
//check if the image is not null (length > 5) only then check imgUrl else display default img
image: new NetworkImage(image.toString().length > 10
? image.toString()
: "https://pbs.twimg.com/profile_images/916384996092448768/PF1TSFOE_400x400.jpg")),
),
),
),
new Padding(
padding:
const EdgeInsets.symmetric(vertical: 16.0, horizontal: 16.0),
child: new Text(
desc,
style: new TextStyle(
fontSize: 18.0,
),
),
),
],
))),
);
}
}
问题日志显示为：
main.dart: Name non-constant identifiers using lowerCamelCase.
post_view.dart: This class (or a class which this class inherits from) is marked as '@immutable', but one or more of its instance fields are not final: PostView.desc, PostView.title, PostView.image
我的编辑器将post_view.dart上的类帖子标记为不可变..我该如何解决。
答案 0 :(得分：0)
final url =
"https://www.googleapis.com/blogger/v3/blogs/MY_BLOG_ID_HERE/posts/?key=API_KEY_HERE";
获取您的博客ID，并将其放入所需的空间，并从博客中获取博客的API密钥
它应该看起来像这样
final url = "https://www.googleapis.com/blogger/v3/blogs/409370562475495748/posts/?key=AIzaSyA3_4OfkfLc10vy5Q2WeUhfirGUUY4J78F8bk";
还尝试制作这些final PostView.desc, PostView.title, PostView.image并查看其是否有效