<uses-permission android:name="android.permission.INTERNET" />

import android.os.AsyncTask;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class FileUploadTask extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        String targetUrl = params[0];
        String filePath = params[1];

        try {
            return uploadFile(targetUrl, filePath);
        } catch (Exception e) {
            return "Error: " + e.getMessage();
        }
    }

    private String uploadFile(String targetUrl, String filePath) throws Exception {
        String boundary = "*****";
        String lineEnd = "\r\n";
        String twoHyphens = "--";

        FileInputStream fileInputStream = null;
        DataOutputStream dataOutputStream = null;

        try {
            File file = new File(filePath);
            fileInputStream = new FileInputStream(file);

            URL url = new URL(targetUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            // 设置连接属性
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Connection", "Keep-Alive");
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);

            dataOutputStream = new DataOutputStream(connection.getOutputStream());
            dataOutputStream.writeBytes(twoHyphens + boundary + lineEnd);
            dataOutputStream.writeBytes("Content-Disposition: form-data; name=\"file\";filename=\"" + file.getName() + "\"" + lineEnd);
            dataOutputStream.writeBytes(lineEnd);

            // 将文件数据写入输出流
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = fileInputStream.read(buffer)) != -1) {
                dataOutputStream.write(buffer, 0, bytesRead);
            }

            dataOutputStream.writeBytes(lineEnd);
            dataOutputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

            // 获取服务器响应
            int responseCode = connection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                // 读取服务器响应
                // ...
                return "File uploaded successfully";
            } else {
                return "File upload failed with response code: " + responseCode;
            }

        } finally {
            // 关闭流
            if (fileInputStream != null) {
                fileInputStream.close();
            }
            if (dataOutputStream != null) {
                dataOutputStream.flush();
                dataOutputStream.close();
            }
        }
    }

    @Override
    protected void onPostExecute(String result) {
        // 处理上传结果
        // result 包含服务器响应或错误消息
    }
}

String targetUrl = "Your server URL here";
String filePath = "Path to your file here";

FileUploadTask fileUploadTask = new FileUploadTask();
fileUploadTask.execute(targetUrl, filePath);