使用MultipartRequest发送post表单数据请求时遇到问题

Question

你好吗？

我正在做一个个人项目，试图使用Flutter将图像+其他信息发送到我的web服务器，使用表单数据格式的post请求。下面是邮递员的一个例子：

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这是我的颤振代码：

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

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

class ConfirmationScreen extends StatefulWidget {
  final XFile? pictureFile;
  final String uri = 'http://127.0.0.1:5000/analyze';
  final Position? position;
  const ConfirmationScreen({this.pictureFile, this.position, Key? key}) : super(key: key);

  @override
  State<ConfirmationScreen> createState() => _ConfirmationScreenState();
}

class _ConfirmationScreenState extends State<ConfirmationScreen> {
  
  Future<void> uploadImage ()async{

    var stream  = http.ByteStream(widget.pictureFile!.openRead());
    stream.cast();

    var length = await widget.pictureFile!.length();

    var uri = Uri.parse('http://127.0.0.1:5000/analyze');

    var request = http.MultipartRequest('POST', uri);

    request.fields['taken_at'] = "18/09/19 01:55:19" ;
    request.fields['latitude'] = widget.position!.latitude.toString();
    request.fields['longitude'] = widget.position!.longitude.toString();
    request.fields['id_camera'] = "2" ;
    request.fields['camera_type'] = "phone" ;
    request.fields['false_alarm'] = '0' ;

    var multiport = http.MultipartFile(
        'file',
        stream,
        length);

    request.files.add(multiport);

    await request.send() ;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("Confirmation")),
      body: Column(
        children: [
          Image.file(File(widget.pictureFile!.path)),
          Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              style: ElevatedButton.styleFrom(
                primary: Colors.red, 
                textStyle: const TextStyle(color: Colors.white)
                ),
              onPressed: (){}, 
              child: const Text("BACK"),),
            const Padding(
              padding: EdgeInsets.fromLTRB(30.0,0,0,0)),
            ElevatedButton(
              style: ElevatedButton.styleFrom(
                primary: Colors.green,
                textStyle: const TextStyle(color: Colors.white)
                ),
              // Image.file(File(widget.pictureFile!.path))
              onPressed: () async {
                uploadImage();
              }, 
              child: const Text("SEND"))
          ],
          ),
          Padding(
          padding: const EdgeInsets.all(8.0), 
          child: Text(
            style: const TextStyle(
              backgroundColor: Colors.white),
              widget.position!.latitude.toString()
              )
              ),
          Padding(
          padding: const EdgeInsets.all(8.0), 
          child: Text(
            style: const TextStyle(
              backgroundColor: Colors.white),
              widget.position!.longitude.toString()
              )
              ),
        ],
      ),
    );
  }
}

这是个简单的屏幕。我只显示图像和两个按钮。一个是将数据发送到web服务器，另一个是返回。

然而，当我按下“发送”按钮时，我得到了这个错误：

E/flutter (30566): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: Connection refused
E/flutter (30566): #0      IOClient.send (package:http/src/io_client.dart:88:7)
E/flutter (30566): <asynchronous suspension>
E/flutter (30566): #1      BaseRequest.send (package:http/src/base_request.dart:133:22)

如果有人能帮我一把，我会非常感激的。祝您今天愉快!

Answer 1

将物理设备和主机连接到同一个wifi网络，并将此行上的URL更改为主机的IP地址。

var uri = Uri.parse('http://127.0.0.1:5000/analyze');

要查找主机的IP地址，请打开命令提示符(用于windows)或终端(用于mac或linux)并键入ipconfig并查找ipv4地址并将127.0.0.1替换为IP Address，这样就可以了。