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GetStringAsync方法调用挂起UI并且永远不会完成

xamarin.ios xamarin asynchronous ios c#

2

pankaj · 技术社区 · 7 年前

我试图使用GetStringAsync方法访问我的url,但调用挂起并且永远不会结束。当我在浏览器中检查它时,它工作得很完美,但不知何故,在我的代码中,它永远不会结束。我的代码:

public bool Login(string url,string userName, string password)
    {
        try
        {
            Task<LoginResponse> response = GetLoginData(url, userName, password);
            if(response.Result.UserInfo.UserId > 0){
                IsAuthenticated = true;
            }
            return IsAuthenticated;
        }
        catch (ArgumentException argex)
        {
            ErrorMessage = argex.Message;
            IsAuthenticated = false;
            return IsAuthenticated;
        }
    }

    public async Task<LoginResponse> GetLoginData(string url, string userName, string password)
    {
        try{
            var param = new AuthenticationParam();
            param.UserName = userName;
            param.Password = password;

            var response = await LoginValidate(url, param);

            response = response.Replace("\"", string.Empty);
            response = response.Replace("\\", "\"");

            LoginResponse list = JsonConvert.DeserializeObject<LoginResponse>(
                response, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });

            return list;
        }
        catch(Exception e){
            System.Diagnostics.Debug.WriteLine(e);
            return new LoginResponse();
        }
    }

    private static async Task<string> LoginValidate(string url, AuthenticationParam param){
        try
        {
            string result = "";
            using (var client = new HttpClient())
            {
                var json_data = string.Empty;
                json_data = JsonConvert.SerializeObject(param);
                var byteArray = Encoding.UTF8.GetBytes(json_data);
                var base64 = Convert.ToBase64String(byteArray);
                url = $"{url}{base64}";
                result = await client.GetStringAsync(url);
                return result;
            }
        }
        catch (Exception ex)
        {
            return "Error: " + ex.Message;
        }
    }

它挂在绳子上 结果=等待客户端。GetStringAsync(url);

1 回复 | 直到 7 年前

1

6

Peter Bons 7 年前

if(response.Result.UserInfo.UserId > 0){ ->。结果是 舞台调度 呼叫并可能导致死锁。在呼叫链上使用wait。

public async Task<bool> Login(string url,string userName, string password)
{
    try
    {
        var response = await GetLoginData(url, userName, password);
        if(response.UserInfo.UserId > 0){
            IsAuthenticated = true;
        }
        return IsAuthenticated;
    }
    catch (ArgumentException argex)
    {
        ErrorMessage = argex.Message;
        IsAuthenticated = false;
        return IsAuthenticated;
    }
}

在调用堆栈中使用 var success = await Login(...);

请阅读 this 关于如何创建此死锁的优秀背景博客文章。