Unity替换WWW为UnityWebRequest遇CS1503错误的解决方案

问题描述 #

Unity提示WWW已被弃用，需改用UnityWebRequest。尝试将原有上传Vuforia目标的代码替换为UnityWebRequest后，出现编译错误：

Assets\Scripts\CloudUpLoading.cs(98,63): error CS1503: 参数2: 无法从“byte[]”转换为“System.Collections.Generic.List<UnityEngine.Networking.IMultipartFormSection>”

错误原因是UnityWebRequest.Post的重载方法不支持直接传入字节数组作为第二个参数，该重载预期接收的是表单分段列表，而非原始字节数据。

修改方案 #

要实现与原WWW相同的功能（发送JSON格式的POST请求），需要改用UnityWebRequest的基础构造方法，配合UploadHandlerRaw处理原始字节数据，同时手动设置请求头。具体步骤如下：

• 移除无用的WWWForm和HttpWebRequest代码（原代码中这两个对象并未实际使用）
• 使用UnityWebRequest构造方法创建POST请求
• 通过UploadHandlerRaw传入JSON字节数据
• 逐个添加请求头，避免引入多余的表单相关头信息

修改后的完整代码 #

using UnityEngine;
using System.Collections;
using System;
using System.Text;
using System.Security.Cryptography;
using System.IO;
using UnityEngine.Networking;

public class PostNewTrackableRequest
{
    public string name;
    public float width;
    public string image;
    public string application_metadata;
}
 
public class CloudUpLoading : MonoBehaviour
{
    public Texture2D texture;
    
    private string access_key = "588f3c9eeb13fe81f6827cced63adca95d6a";
    private string secret_key = "77e56b7cac04b83d8ce55c13dd047e8acbbe";
    private string url = @"https://vws.vuforia.com";
    private string targetName = "Target_Hosted"; // 上传新目标时需修改，避免与云端已有目标重名
    
    public void CallPostTarget()
    {
        StartCoroutine(PostNewTarget());
    }
    
    IEnumerator PostNewTarget()
    {
        string requestPath = "/targets";
        string serviceURI = url + requestPath;
        string httpAction = "POST";
        string contentType = "application/json";
        string date = string.Format("{0:r}", DateTime.Now.ToUniversalTime());
    
        Debug.Log(date);
    
        // 处理纹理转为RGB24格式的PNG
        Texture2D tex = new Texture2D(texture.width, texture.height, TextureFormat.RGB24, false);
        tex.SetPixels(texture.GetPixels());
        tex.Apply();
        byte[] image = tex.EncodeToPNG();
    
        // 构造请求模型
        string metadataStr = "Target Image Detected";
        byte[] metadata = ASCIIEncoding.ASCII.GetBytes(metadataStr);
        PostNewTrackableRequest model = new PostNewTrackableRequest();
        model.name = targetName;
        model.width = 64.0f;
        model.image = Convert.ToBase64String(image);
        model.application_metadata = Convert.ToBase64String(metadata);
        string requestBody = JsonUtility.ToJson(model);
    
        // 计算Content-MD5
        MD5 md5 = MD5.Create();
        var contentMD5bytes = md5.ComputeHash(Encoding.ASCII.GetBytes(requestBody));
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < contentMD5bytes.Length; i++)
        {
            sb.Append(contentMD5bytes[i].ToString("x2"));
        }
        string contentMD5 = sb.ToString();
    
        // 计算签名
        string stringToSign = string.Format("{0}\n{1}\n{2}\n{3}\n{4}", httpAction, contentMD5, contentType, date, requestPath);
        HMACSHA1 sha1 = new HMACSHA1(Encoding.ASCII.GetBytes(secret_key));
        byte[] sha1Hash = sha1.ComputeHash(Encoding.ASCII.GetBytes(stringToSign));
        string signature = Convert.ToBase64String(sha1Hash);
    
        Debug.Log("<color=green>Signature: "+signature+"</color>");
    
        // 创建UnityWebRequest并配置参数
        UnityWebRequest www = new UnityWebRequest(serviceURI, httpAction);
        byte[] bodyRaw = Encoding.UTF8.GetBytes(requestBody);
        www.uploadHandler = new UploadHandlerRaw(bodyRaw);
        www.downloadHandler = new DownloadHandlerBuffer();
    
        // 设置请求头
        www.SetRequestHeader("Host", url);
        www.SetRequestHeader("Date", date);
        www.SetRequestHeader("Content-Type", contentType);
        www.SetRequestHeader("Authorization", string.Format("VWS {0}:{1}", access_key, signature));
    
        // 发送请求
        yield return www.SendWebRequest();
    
        // 处理响应
        if (www.result != UnityWebRequest.Result.Success)
        {
            Debug.Log("request error: " + www.error);
        }
        else
        {
            Debug.Log("request success");
            Debug.Log("returned data: " + www.downloadHandler.text);
        }
        
        // 清理资源
        www.Dispose();
    }
}

关键修改点说明 #

• 移除原代码中未使用的WWWForm和HttpWebRequest实例，减少冗余代码
• 使用UnityWebRequest构造方法指定请求方法为POST，配合UploadHandlerRaw传递JSON字节数据
• 用SetRequestHeader方法逐个添加必要的请求头，避免引入WWWForm自带的表单相关头信息
• 添加www.Dispose()手动释放资源，符合Unity资源管理规范
• 通过downloadHandler.text获取响应内容，替代原WWW.text

内容的提问来源于stack exchange，提问作者ashah