Unity WebRequest实现下载信息回传并更新UI

问题背景 #

我有三个脚本：MenuManager、NetworkManager和自定义HttpClient。点击按钮会调用MenuManager的方法，触发NetworkManager从Asp.net后端下载数据。需要实现HttpClient将文件大小、下载速度、已下载总字节数实时回传给NetworkManager，再由NetworkManager传递到MenuManager更新UI。之前的修改尝试未成功，以下是正确的修改方案：

1. 修改HttpClient脚本 #

为PostWithProgress方法添加进度回调参数，在下载循环中实时触发回调，传递下载进度、速度、文件大小和已下载字节数：

public static async Task<T> PostWithProgress<T>(string endpoint, object payload, Action<float, float, long, ulong> progressCallback, string header = null)
{
    var postRequest = CreateRequest(endpoint, RequestType.POST, payload);

    if (!string.IsNullOrEmpty(header))
        AttachHeader(postRequest, "Bearer ", header);

    postRequest.SendWebRequest();
    long fileSize = long.Parse(postRequest.GetResponseHeader("Content-Length"));
    ulong previousBytes = 0;
    float lastTime = Time.time;

    while (!postRequest.isDone)
    {
        float currentTime = Time.time;
        float timeDelta = currentTime - lastTime;
        if (timeDelta <= 0)
        {
            await Task.Delay(10);
            continue;
        }

        // 计算进度、已下载字节
        float progress = postRequest.downloadProgress;
        ulong bytesDownloaded = postRequest.downloadedBytes;
        // 计算下载速度（字节/秒）
        float downloadSpeed = (bytesDownloaded - previousBytes) / timeDelta;

        // 实时触发回调，传递数据
        progressCallback?.Invoke(progress * 100, downloadSpeed, fileSize, bytesDownloaded);

        previousBytes = bytesDownloaded;
        lastTime = currentTime;
        await Task.Delay(10);
    }

    if (postRequest.isNetworkError || string.IsNullOrEmpty(postRequest.downloadHandler.text))
    {
        string errorMessage = "";
        if (!postRequest.isHttpError)
        {
            errorMessage = postRequest.isNetworkError ? "Network Error" :
                         string.IsNullOrEmpty(postRequest.downloadHandler.text) ? "Empty Response" :
                         postRequest.error ?? "Test null";
        }
        else
        {
            errorMessage = "Internal Server Error";
        }
        GameObject.FindObjectOfType<ErrorLogger>(true).LogError(errorMessage, "Error: " + errorMessage);
        return default;
    }

    try
    {
        return JsonConvert.DeserializeObject<T>(postRequest.downloadHandler.text);
    }
    catch
    {
        GameObject.FindObjectOfType<ErrorLogger>(true).LogError(postRequest.downloadHandler.text, postRequest.downloadHandler.text);
        return default;
    }
}

修改说明：

• 添加Action<float, float, long, ulong> progressCallback参数，用于传递实时进度
• 优化下载速度计算：通过记录上一次的已下载字节和时间，计算时间差内的字节增量，得到更准确的实时速度
• 在循环中每次计算后调用progressCallback，传递进度（转为百分比）、速度、文件大小、已下载字节数

2. 修改NetworkManager脚本 #

更新DownloadPlayerInfo方法，接收MenuManager传入的回调参数，并传递给HttpClient，同时在回调触发时直接转发给MenuManager：

public async Task DownloadPlayerInfo(Action<float, float, long, ulong> progressCallback)
{
    UserInfoRequest req = new UserInfoRequest() { UID = UID };
    var response = await HttpClient.PostWithProgress<UserInfoResponse>(userInfoEndpoint, req, progressCallback, PlayerToken);
    HandleUserInfoResponse(response);
}

修改说明：

• 方法参数添加Action<float, float, long, ulong> progressCallback
• 调用PostWithProgress时传入该回调，HttpClient的实时进度会直接通过这个回调传递给MenuManager
• 下载完成后处理响应数据

3. 修改MenuManager脚本 #

在DownloadPlayerInfo方法中传入回调，实时接收进度数据并更新UI：

private async Task DownloadPlayerInfo()
{
    LoginPanal?.SetActive(false);
    RegisterPanal?.SetActive(false);
    // 传入进度回调，实时更新UI
    await networkManager.DownloadPlayerInfo((progress, speed, fileSize, bytesDownloaded) =>
    {
        UpdateDownloadProgress(progress, speed, fileSize, bytesDownloaded);
    });
}

private void UpdateDownloadProgress(float progress, float downloadSpeed, long fileSize, ulong bytesDownloaded)
{
    float speed = 0f;
    string abbreviation = "B/s";

    if (downloadSpeed >= 1024 * 1024)
    {
        speed = downloadSpeed / (1024 * 1024);
        abbreviation = "MB/s";
    }
    else if (downloadSpeed >= 1024)
    {
        speed = downloadSpeed / 1024;
        abbreviation = "KB/s";
    }
    else
    {
        speed = downloadSpeed;
        abbreviation = "B/s";
    }

    DownloadInfoText.text = $"{speed:F1} {abbreviation} Progress: {progress:F2}% " +
                            $"({bytesDownloaded / (1024f * 1024f):F1}MB / {fileSize / (1024f * 1024f):F1}MB)";
}

修改说明：

• 调用networkManager.DownloadPlayerInfo时传入匿名回调函数，接收进度数据
• 修复变量名拼写错误（abriviation → abbreviation）
• 计算MB时使用1024f避免整数除法导致的精度丢失

内容的提问来源于stack exchange，提问作者Rudolf