Flutter :上传文件到存储时如何使用百分比的线性进度条

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

Future<void> uploadFile(File file) async {
  String url = 'https://your-upload-endpoint.com'; // 上传文件的接口地址

  var request = http.MultipartRequest('POST', Uri.parse(url));
  request.files.add(await http.MultipartFile.fromPath('file', file.path));

  var response = await request.send();
  if (response.statusCode == 200) {
    print('文件上传成功');
  } else {
    print('文件上传失败');
  }
}

import 'package:flutter/material.dart';
import 'dart:io';

class UploadPage extends StatefulWidget {
  @override
  _UploadPageState createState() => _UploadPageState();
}

class _UploadPageState extends State<UploadPage> {
  double _progress = 0.0;
  File _selectedFile;

  void _selectFile() async {
    // 文件选择逻辑
    FilePickerResult result = await FilePicker.platform.pickFiles();
    if (result != null) {
      setState(() {
        _selectedFile = File(result.files.single.path);
      });
    }
  }

  void _uploadFile() async {
    if (_selectedFile != null) {
      await uploadFile(_selectedFile);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('文件上传'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            LinearProgressIndicator(
              value: _progress, // 设置进度条的值
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _selectFile,
              child: Text('选择文件'),
            ),
            ElevatedButton(
              onPressed: _uploadFile,
              child: Text('上传文件'),
            ),
          ],
        ),
      ),
    );
  }
}