flutter图片上传

Flutter 图片上传可以通过以下步骤实现：

1. 导入相关依赖：

dependencies:
  dio: ^4.0.0
  flutter_image_compress: ^0.9.0
  image_picker: ^0.8.3+2

2. 添加权限：

在 `AndroidManifest.xml` 中添加以下权限：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.CAMERA"/>

在 `Info.plist` 中添加以下权限：

<key>NSCameraUsageDescription</key>
<string>使用相机拍照上传图片</string>
<key>NSPhotoLibraryUsageDescription</key>
<string>使用相册选取图片上传</string>

3. 实现选择图片功能：

final ImagePicker _picker = ImagePicker();
XFile? _imageFile;

Future<void> _getImage(ImageSource source) async {
  final pickedFile = await _picker.pickImage(source: source);
  if (pickedFile != null) {
    setState(() {
      _imageFile = pickedFile;
    });
  }
}

4. 实现图片压缩：

import 'dart:io';
import 'package:flutter_image_compress/flutter_image_compress.dart';

Future<File> _compressImage(File file) async {
  final result = await FlutterImageCompress.compressAndGetFile(
    file.absolute.path,
    file.absolute.path,
    quality: 50,
  );
  return result!;
}

5. 实现上传图片功能：

import 'dart:io';
import 'package:dio/dio.dart';

void _uploadImage() async {
  if (_imageFile == null) return;

  final file = File(_imageFile!.path);
  final compressedFile = await _compressImage(file);

  final formData = FormData.fromMap({
    'file': await MultipartFile.fromFile(compressedFile.path),
  });

  final response = await Dio().post(
    'https://example.com/upload',
    data: formData,
  );

  if (response.statusCode == 200) {
    print('上传成功');
  } else {
    print('上传失败');
  }
}

完整代码示例：

import 'dart:io';
import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:flutter_image_compress/flutter_image_compress.dart';
import 'package:image_picker/image_picker.dart';

class ImageUploadPage extends StatefulWidget {
  const ImageUploadPage({Key? key}) : super(key: key);

  @override
  _ImageUploadPageState createState() => _ImageUploadPageState();
}

class _ImageUploadPageState extends State<ImageUploadPage> {
  final ImagePicker _picker = ImagePicker();
  XFile? _imageFile;

  Future<void> _getImage(ImageSource source) async {
    final pickedFile = await _picker.pickImage(source: source);
    if (pickedFile != null) {
      setState(() {
        _imageFile = pickedFile;
      });
    }
  }

  Future<File> _compressImage(File file) async {
    final result = await FlutterImageCompress.compressAndGetFile(
      file.absolute.path,
      file.absolute.path,
      quality: 50,
    );
    return result!;
  }

  void _uploadImage() async {
    if (_imageFile == null) return;

    final file = File(_imageFile!.path);
    final compressedFile = await _compressImage(file);

    final formData = FormData.fromMap({
      'file': await MultipartFile.fromFile(compressedFile.path),
    });

    final response = await Dio().post(
      'https://example.com/upload',
      data: formData,
    );

    if (response.statusCode == 200) {
      print('上传成功');
    } else {
      print('上传失败');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('上传图片'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            if (_imageFile != null)
              Image.file(File(_imageFile!.path))
            else
              const Text('请选择图片'),
            ElevatedButton(
              onPressed: () => _getImage(ImageSource.camera),
              child: const Text('拍照'),
            ),
            ElevatedButton(
              onPressed: () => _getImage(ImageSource.gallery),
              child: const Text('选择图片'),
            ),
            ElevatedButton(
              onPressed: _uploadImage,
              child: const Text('上传图片'),
            ),
          ],
        ),
      ),
    );
  }
}