[英]Backgroundworker and UI interactivity
我正在使用后台工作者進行耗時的操作(要將一些數據上傳到服務器並從服務器下載一些數據)。 所有服務器通信都是通過http請求(GET,POST,PUT,Delete)進行的,而我使用的代碼是
private void btnSync_Click(object sender, RoutedEventArgs e)
{
btnSync.IsEnabled = false;
BackgroundWorker syncWorker = new BackgroundWorker();
syncWorker.WorkerReportsProgress = true;
syncWorker.WorkerSupportsCancellation = true;
syncWorker.DoWork+=new DoWorkEventHandler(syncWorker_DoWork);
syncWorker.ProgressChanged+=new ProgressChangedEventHandler(syncWorker_ProgressChanged);
syncWorker.RunWorkerCompleted+=new RunWorkerCompletedEventHandler(syncWorker_RunWorkerCompleted);
syncWorker.RunWorkerAsync();
}
private void syncWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker target = (BackgroundWorker)sender;
foreach (...........) // a loop to do some set of actions on some objects
{
target.ReportProgress(1, obj);
target.ReportProgress(2, obj);
target.ReportProgress(3, obj);
}
target.ReportProgress(4);
}
private void syncWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
if (e.ProgressPercentage == 1)
{
string id= e.UserState.ToString();
mySyncHelper.DOGETFROMServer(id); //Issue a GET request and read and process resposne (deserialize json data and insert to local DB)
}
if (e.ProgressPercentage == 2)
{
string id= e.UserState.ToString();
mySyncHelper.DOGETFROMServer(id);//Issue a GET request and read and process resposne(deserialize json data and insert to local DB)
}
if (e.ProgressPercentage == 3)
{
string id= e.UserState.ToString();
mySyncHelper.DOGETFROMServer(id);//Issue a GET request and read and process resposne (deserialize json data and insert/Update response data to local DB)
}
if (e.ProgressPercentage ==4)
{
mySyncHelper.DOPOSTToServer();//Issue a POST request and read and process resposne (deserialize json data and insert/Update response data to local DB)
mySyncHelper.DOPUTToServer();
mySyncHelper.DODELETEToServer();
}
}
private void syncWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
txtSyncStatus.Visibility = Visibility.Visible;
txtSyncStatus.Text = string.Concat(DbookLanguage.message_error, Environment.NewLine , e.Error.Message.ToString());
}
else
{
btnSync.IsEnabled = true;
txtSyncStatus.Text = "";
}
}
我面臨的問題是@應用程序在某些階段等待一段時間以獲取對http請求的響應,並且在此狀態下,整個應用程序進入凍結狀態。 我用於從服務器獲取響應的代碼是var httpResponse =(HttpWebResponse)httpWebRequest.GetResponse();。 在此狀態下,應用程序無響應。
我該如何預防呢? 是使一系列Http請求並使應用程序UI交互的其他好方法嗎
如注釋中所建議,“ ProgressChanged”中的代碼在UI線程上運行,這導致UI凍結(因為此處理程序中有服務器請求)。
ProgressChanged
處理程序僅在您進行了一些常規的UI更新(例如已完成的百分比)時才有用(應該使用)。 在您的情況下,請考慮將整個代碼移至新方法(例如GetFromServer(int id)
),然后從DoWork內部對該方法進行調用。 這將導致所有這些I / O工作在后台線程上運行。
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