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此Http请求的替代方案

windows-phone windows-phone-7 c#

deanvmc · 技术社区 · 14 年前

我有一个类去获取一些数据并将其作为字符串返回。当这个对象工作时,有一个旋转图标让用户知道工作正在完成。问题是代码在响应返回之前退出。我坚持了一个

while(response == null)

response = (HttpWebResponse)request.EndGetResponse(AsyncResult);

不是开火。它在控制台应用程序中触发ok,所以我将此归结为silverlight不喜欢的事情,下面是完整的代码:

public class HttpWorker
{
    private HttpWebRequest request;
    private HttpWebResponse response;
    private string responseAsString;
    private string url;

    public HttpWorker()
    {

    }

    public string ReadFromUrl(string Url)
    {
        url = Url;
        request = (HttpWebRequest)WebRequest.Create(url);

        request.CookieContainer = new CookieContainer();
        request.AllowAutoRedirect = true;
        request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.6) Gecko/20060728 Firefox/1.5.0.6";

        AsyncRequest(); // The Demon!

        return responseAsString;
    }

    private void AsyncRequest()
    {
        request.BeginGetResponse(new AsyncCallback(FinaliseAsyncRequest), null);
    }

    private void FinaliseAsyncRequest(IAsyncResult AsyncResult)
    {
        response = (HttpWebResponse)request.EndGetResponse(AsyncResult);


        if (response.StatusCode == HttpStatusCode.OK)
        {
            // Create the stream, encoder and reader.
            Stream responseStream = response.GetResponseStream();
            Encoding streamEncoder = Encoding.UTF8;
            StreamReader responseReader = new StreamReader(responseStream, streamEncoder);
            responseAsString = responseReader.ReadToEnd();
        }
        else
        {
            throw new Exception(String.Format("Response Not Valid {0}", response.StatusCode));
        }
    }

}

3 回复 | 直到 14 年前

JSBÕ±Õ¸Õ£Õ¹ 14 年前

你是不是在忙着 (while response == null) 在UI线程上?的异步回调 HttpRequest 将在UI线程上传递,因此如果在同一线程上循环,则回调永远无法运行。您需要返回以允许主消息循环运行,然后将传递异步回调。

上面的设计表明,无论如何,您真正需要的是同步获取。忘记回电话,直接打 FinaliseAsyncRequest ReadFromUrl 你自己。用户界面将一直挂起,直到请求完成,但听起来这就是您想要的。

Mick N 14 年前

我在这里发布了一个使用WebClient和HttpWebRequest的工作示例。

WebClient, HttpWebRequest and the UI Thread on Windows Phone 7

请随意重用代码。

Community Mike Kinghan 7 年前

从web服务器获取字符串的最简单方法是 WebClient.DownloadStringAsync() MSDN docs ).

试试这样的:

private void DownloadString(string address)
{
    WebClient client = new WebClient();
    Uri uri = new Uri(address);

    client.DownloadStringCompleted += DownloadStringCallback;
    client.DownloadStringAsync(uri);

    StartWaitAnimation();
}


private void DownloadStringCallback(object sender, DownloadStringCompletedEventArgs e)
{
    // Do something with e.Result (which is the returned string)

    StopWaitAnimation();
}

如果你真的要模仿同步行为,看看 Faking synchronous calls in Silverlight WP7