標籤：blog http 資料 art io 問題
WebClient的逾時問題及解決
轉自：http://blog.163.com/[email protected]/blog/static/62440288201112245345838/
Webclient在下載請求時無法佈建要求逾時時間和請求讀寫逾時時間。WebClient在非同步下載時遇到網路不通等問題時沒有響應逾時造成app掛起。
1.Webclient請求逾時設定
重寫Webclient的GetWebRequest方法，為HttpWebRequest添加請求逾時及讀寫逾時
protected override WebRequest GetWebRequest(Uri address)
{
HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
request.Timeout = 1000 * Timeout;
request.ReadWriteTimeout = 1000 * Timeout;
return request;
}
2.WebClient在非同步下載
建立計時器監視響應情況，到期則取消下載
public class Calculagraph
{
/// <summary>
/// 時間到事件
/// </summary>
public event TimeoutCaller TimeOver;
/// <summary>
/// 開始時間
/// </summary>
private DateTime _startTime;
private TimeSpan _timeout = new TimeSpan(0, 0, 10);
private bool _hasStarted = false;
object _userdata;
/// <summary>
/// 計時器構造方法
/// </summary>
/// <param name="userdata">計時結束時回調的使用者資料</param>
public Calculagraph(object userdata)
{
TimeOver += new TimeoutCaller(OnTimeOver);
_userdata = userdata;
}
/// <summary>
/// 逾時退出
/// </summary>
/// <param name="userdata"></param>
public virtual void OnTimeOver(object userdata)
{
Stop();
}
/// <summary>
/// 到期時間(秒)
/// </summary>
public int Timeout
{
get
{
return _timeout.Seconds;
}
set
{
if (value <= 0)
return;
_timeout = new TimeSpan(0, 0, value);
}
}
/// <summary>
/// 是否已經開始計時
/// </summary>
public bool HasStarted
{
get
{
return _hasStarted;
}
}
/// <summary>
/// 開始計時
/// </summary>
public void Start()
{
Reset();
_hasStarted = true;
Thread th = new Thread(WaitCall);
th.IsBackground = true;
th.Start();
}
/// <summary>
/// 重設
/// </summary>
public void Reset()
{
_startTime = DateTime.Now;
}
/// <summary>
/// 停止計時
/// </summary>
public void Stop()
{
_hasStarted = false;
}
/// <summary>
/// 檢查是否到期
/// </summary>
/// <returns></returns>
private bool checkTimeout()
{
return (DateTime.Now - _startTime).Seconds >= Timeout;
}
private void WaitCall()
{
try
{
//迴圈檢測是否到期
while (_hasStarted && !checkTimeout())
{
Thread.Sleep(1000);
}
if (TimeOver != null)
TimeOver(_userdata);
}
catch (Exception)
{
Stop();
}
}
}
/// <summary>
/// 到期時回調委託
/// </summary>
/// <param name="userdata"></param>
public delegate void TimeoutCaller(object userdata);
public class CNNWebClient : WebClient
{
private Calculagraph _timer;
private int _timeOut = 10;
/// <summary>
/// 到期時間
/// </summary>
public int Timeout
{
get
{
return _timeOut;
}
set
{
if (value <= 0)
_timeOut = 10;
_timeOut = value;
}
}
/// <summary>
/// 重寫GetWebRequest,添加WebRequest對象逾時時間
/// </summary>
/// <param name="address"></param>
/// <returns></returns>
protected override WebRequest GetWebRequest(Uri address)
{
HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
request.Timeout = 1000 * Timeout;
request.ReadWriteTimeout = 1000 * Timeout;
return request;
}
/// <summary>
/// 帶到期計時的下載
/// </summary>
public void DownloadFileAsyncWithTimeout(Uri address, string fileName, object userToken)
{
if (_timer == null)
{
_timer = new Calculagraph(this);
_timer.Timeout = Timeout;
_timer.TimeOver += new TimeoutCaller(_timer_TimeOver);
this.DownloadProgressChanged += new DownloadProgressChangedEventHandler(CNNWebClient_DownloadProgressChanged);
}
DownloadFileAsync(address, fileName, userToken);
_timer.Start();
}
/// <summary>
/// WebClient下載過程事件，接收到資料時引發
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void CNNWebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
_timer.Reset();//重設計時器
}
/// <summary>
/// 計時器到期
/// </summary>
/// <param name="userdata"></param>
void _timer_TimeOver(object userdata)
{
this.CancelAsync();//取消下載
}
}
