Dart http库

最基本的获取数据

import 'package:http/http.dart' as http;

main(List<String> args) async {
  var url =  Uri.http('localhost:5000', '/test');
  var r = await http.get(url);
  print(r.body); // hello world
  print(r.statusCode); // 服务器返回的状态码200
}

服务器抛出错误

import 'package:http/http.dart' as http;

main(List<String> args) async {
  var url =  Uri.http('localhost:5000', '/test');
  var r = await http.get(url);
  print(r.body); // {"statusCode":500,"error":"Internal Server Error","message":"服务器错误"}
  print(r.statusCode); // 500
}

抓取请求错误

try {
  var r = await http.get('http://closeExample.com');
  print(r.statusCode);
} on SocketException catch (e) {
  print(e); // SocketException: Failed host lookup: 'closeexample.com' (OS Error: No address associated with hostname, errno = 7)
}

在指定的时间中断请求

import 'package:http/http.dart' as http;

main(List<String> args) async {
  var client = http.Client();
  
  Future.delayed(Duration(seconds: 5)).then((_) {
    print('关闭这个请求');
    client.close();
  });
  
  try {
    var url = Uri.http('localhost:5000', '/test');
    print('请求开始');
    var r = await client.get(url);
    print(r.body);
    print(r.statusCode);
  } on http.ClientException catch(e) {
    /// 捕获中断后抛出的错误
    print(e);
  } catch (e) {
    print('Other Error: $e');
  }
}

  @Get('test')
  async getHello(): Promise<string> {
    //延迟 10s后发出数据
    return await new Promise(res => {
      setTimeout(() => {
        res('hello world');
      }, 10000);
    });
  }

打印结果

$ dart ./bin/main.dart
请求开始
关闭这个请求
Connection closed before full header was received

发送文件到服务器

客服端：

import 'dart:io';
import 'package:path/path.dart' as path;
import 'package:http/http.dart';

String __filename = Platform.script.path.replaceFirst('/', '');
String __dirname = path.dirname(__filename);

main(List<String> arguments) async {
  var uri = Uri.parse("http://localhost:3000/upload");

  MultipartRequest request = MultipartRequest("POST", uri);

  request.fields['user'] = 'Ajanuw';

  request.files.add(
    await MultipartFile.fromPath('file', path.join(__dirname, 'test.jpg')),
  );
  var r = await request.send();
  print(r.statusCode);
  print(await r.stream.bytesToString());
}

服务器端代码片段：

  @Post('upload')
  @UseInterceptors(FileInterceptor('file'))
  UploadedFile(@UploadedFile() file, @Body() body) {
    console.log(file);
    console.log(body);
    const writeImage = createWriteStream(
      join(__dirname, '..', 'upload', `${file.originalname}`),
    );
    writeImage.write(file.buffer);
    return 'ok';
  }

执行客服端代码：

λ dart ./bin/main.dart
201
ok

服务端打印：

[0] { fieldname: 'file',
[0]   originalname: 'test.jpg',
[0]   encoding: '7bit',
[0]   mimetype: 'application/octet-stream',
[0]   buffer:
[0]    <Buffer ff d8 ff e0 00 10 4a 46 49 46 00 01 01 00 00 01 00 01 00 00 ff fe 00 3b 43 52 45 41 54 4f 52 3a 20 67 64 2d 6a 70 65 67 20 76 31 2e 30 20 28 75 73 69 ... >,
[0]   size: 341398 }
[0] [Object: null prototype] { user: 'Ajanuw' }

获取文件下载进度

使用send方法发送，可以返回一个监听流

import 'dart:io';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

  Uint8List image;
  ImageChunkEvent loadingProgress;
  ImageNetworkError error;
  var _client = http.Client();

  /// request
  http.Request get _req {
    var req = http.Request(
      'get',
      Uri.parse(widget.src),
    );
    if (widget.headers != null) {
      for (MapEntry<String, String> m in widget.headers.entries) {
        req.headers[m.key] = m.value;
      }
    }
    return req;
  }

  @override
  void initState() {
    super.initState();
    _init();
  }

  Future<void> _init() async {
    http.StreamedResponse r = await _client.send(_req);
    print(r.statusCode);
    List<int> ds = [];
    r.stream.listen(
      (List<int> d) {
        ds.addAll(d);
        setState(() {
          loadingProgress = ImageChunkEvent(
            cumulativeBytesLoaded: ds.length, // 当前加载
            expectedTotalBytes: r.contentLength, // 总长度
          );
        });
      },
      onDone: () {
        setState(() {
          image = Uint8List.fromList(ds);
          loadingProgress = null;
        });
        _client?.close();
      },
    );
  }

  @override
  void dispose() {
    _client?.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    if (loadingProgress == null &&
        image == null &&
        widget.loadingWidget != null) {
      return _loadingWidget();
    }
    if (widget.loadingBuilder != null) {
      return _loadingBuilder();
    } else {
      return Image.memory(image);
    }
  }
}

创建自己的request

import 'dart:convert';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

final SkyClient skyClient = SkyClient(http.Client());
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Text('home page'),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.send),
        onPressed: () async {
          try {
            var r = await skyClient.getFirstUser('januwA');
            print(r);
          } on SocketException catch (e) {
            print(e);
          }
        },
      ),
    );
  }
}

class SkyClient extends http.BaseClient {
  final http.Client _inner;

  SkyClient(this._inner);

  @override
  Future<http.StreamedResponse> send(http.BaseRequest request) {
    return _inner.send(request);
  }

  @override
  Future<http.Response> get(url, {Map<String, String> headers}) {
    return _inner.get(url, headers: headers);
  }

  Future<Map<String, dynamic>> getFirstUser(String name,
      {Map<String, String> headers}) async {
    var r = await _inner.get("https://api.github.com/search/users?q=$name",
        headers: headers);
    return jsonDecode(r.body)['items'][0];
  }
}

上传文件获取上传进度

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'package:path/path.dart' as path;
import 'package:http/http.dart' as http;

final String __filename = Platform.script.path.replaceFirst('/', '');
final String __dirname = path.dirname(__filename);
final Uri uri = Uri.parse("http://localhost:3000/upload");
final String imgPath = path.join(__dirname, 'test.jpg');
main() async {
  final request = await HttpClient().postUrl(uri);
  int byteCount = 0;

  var requestMultipart = http.MultipartRequest("POST", uri)
    ..files.addAll([
      await http.MultipartFile.fromPath("file", imgPath),
    ])
    ..fields.addEntries([
      MapEntry("name", "ajanuw"),
    ]);

  request.contentLength = requestMultipart.contentLength;

  var msStream = requestMultipart.finalize();
  requestMultipart.headers.forEach((k, v) => request.headers.set(k, v));

  await request.addStream(msStream.transform(
    StreamTransformer.fromHandlers(
      handleData: (data, sink) {
        sink.add(data);
        byteCount += data.length;
        print(
            "${((byteCount / requestMultipart.contentLength) * 100).toInt()}/${100}");
      },
      handleError: (error, stack, sink) => print('upload error'),
      handleDone: (sink) => sink.close(),
    ),
  ));

  final httpResponse = await request.close();
  print(httpResponse.statusCode);

  var contents = StringBuffer();
  httpResponse.transform(utf8.decoder).listen(
    (String data) => contents.write(data),
    onDone: () {
      print(contents.toString());
    },
  );
}

run

> dart .inmain.dart
0/100
0/100
80/100
99/100
99/100
100/100
201
upload sucess

serevr

@Post('upload')
@UseInterceptors(FileInterceptor('file'))
UploadedFile(@UploadedFile() file) {
  console.log(file);
  return "upload sucess";
}

上传文件获取上传进度(2)

import 'dart:async';
import 'dart:io';
import 'package:path/path.dart' as path;
import 'package:http/http.dart' as http;

final String __filename = Platform.script.path.replaceFirst('/', '');
final String __dirname = path.dirname(__filename);
final Uri uri = Uri.parse("http://localhost:3000/upload");
final String imgPath = path.join(__dirname, 'test.jpg');

class MultipartRequest extends http.MultipartRequest {
  Function(int bytes, int total) onProgress;
  MultipartRequest(String method, Uri url, {this.onProgress})
      : super(method, url);
  
  /// 重写这个方法
  @override
  http.ByteStream finalize() {
    final byteStream = super.finalize();
    if (onProgress == null) return byteStream;
    final total = this.contentLength;
    int bytes = 0;

    final t = StreamTransformer.fromHandlers(
      handleData: (List<int> data, EventSink<List<int>> sink) {
        bytes += data.length;
        onProgress(bytes, total);
        sink.add(data);
      },
    );
    final stream = byteStream.transform(t);
    return http.ByteStream(stream);
  }
}

main() async {
  var uri = Uri.parse("http://localhost:3000/upload");

  http.MultipartRequest request = MultipartRequest(
    "POST",
    uri,
    onProgress: (int bytes, int total) {
      print("${((bytes / total) * 100).toInt()}/${100}");
    },
  );
  request.files.add(
    await http.MultipartFile.fromPath('file', path.join(__dirname, 'test.jpg')),
  );
  var r = await request.send();
  print(r.statusCode);
  print(await r.stream.bytesToString());
}
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原文地址：https://www.cnblogs.com/ajanuw/p/10999826.html