/// <summary>
/// This method should be used to call methods from siteutils that might take a few seconds.
/// It makes sure only on thread at a time executes and has a timeout for the execution.
/// It also catches Exceptions from the utils and writes errors to the log, and show a message on the GUI.
/// The Wait Cursor will be shown on while executing the task and the resultHandler will be called on the MPMain thread.
/// </summary>
/// <param name="task">method to invoke on a background thread</param>
/// <param name="resultHandler">method to invoke on the GUI Thread with the result of the task</param>
/// <param name="taskDescription">description of the tak to be invoked - will be shown in the error message if execution fails or times out</param>
/// <param name="timeout">true: use the timeout, or false: wait forever</param>
/// <returns>true, if the task could be successfully started in the background</returns>
internal bool ExecuteInBackgroundAndCallback(Func<object> task, Action<bool, object> resultHandler, string taskDescription, bool timeout)
{
// make sure only one background task can be executed at a time
if (!IsBusy && Monitor.TryEnter(this))
{
try
{
IsBusy = true;
abortedByUser = false;
_CurrentResultHandler = resultHandler;
_CurrentTaskDescription = taskDescription;
_CurrentResult = null;
_CurrentError = null;
_CurrentTaskSuccess = null;// while this is null the task has not finished (or later on timeouted), true indicates successfull completion and false error
GUIWaitCursor.Init(); GUIWaitCursor.Show(); // init and show the wait cursor in MediaPortal
backgroundThread = new Thread(delegate()
{
try
{
_CurrentResult = task.Invoke();
_CurrentTaskSuccess = true;
}
catch (ThreadAbortException)
{
if (!abortedByUser) Log.Warn("Timeout waiting for results.");
Thread.ResetAbort();
}
catch (Exception threadException)
{
_CurrentError = threadException as OnlineVideosException;
Log.Warn(threadException.ToString());
_CurrentTaskSuccess = false;
}
timeoutTimer.Stop();
// hide the wait cursor
GUIWaitCursor.Hide();
// execute the ResultHandler on the Main Thread
GUIWindowManager.SendThreadCallbackAndWait((p1, p2, o) => { ExecuteTaskResultHandler(); return 0; }, 0, 0, null);
}) { Name = "HeadWeb", IsBackground = true };
// disable timeout when debugging
if (timeout && !System.Diagnostics.Debugger.IsAttached) timeoutTimer.Start();
backgroundThread.Start();
// successfully started the background task
return true;
}
catch (Exception ex)
{
Log.Error(ex);
IsBusy = false;
_CurrentResultHandler = null;
GUIWaitCursor.Hide(); // hide the wait cursor
return false; // could not start the background task
}
}
else
{
Log.Error("Another thread tried to execute a task in background.");
return false;
}
}
void ExecuteTaskResultHandler()
{
if (!IsBusy) return;
// show an error message if task was not completed successfully
if (_CurrentTaskSuccess != true)
{
if (_CurrentError != null)
{
MediaPortal.Dialogs.GUIDialogOK dlg_error = (MediaPortal.Dialogs.GUIDialogOK)GUIWindowManager.GetWindow((int)GUIWindow.Window.WINDOW_DIALOG_OK);
if (dlg_error != null)
{
dlg_error.Reset();
dlg_error.SetHeading("HeadWeb");
dlg_error.SetLine(1, string.Format("{0} {1}", "Error", _CurrentTaskDescription));
dlg_error.SetLine(2, _CurrentError.Message);
dlg_error.DoModal(GUIWindowManager.ActiveWindow);
}
}
else
{
GUIDialogNotify dlg_error = (GUIDialogNotify)GUIWindowManager.GetWindow((int)GUIWindow.Window.WINDOW_DIALOG_NOTIFY);
if (dlg_error != null)
{
dlg_error.Reset();
//dlg_error.SetImage(GUIOnlineVideos.GetImageForSite("OnlineVideos", type:"Icon"));
dlg_error.SetHeading("HeadWeb");
if (_CurrentTaskSuccess.HasValue)
dlg_error.SetText(string.Format("{0} {1}", "Error", _CurrentTaskDescription));
else
dlg_error.SetText(string.Format("{0} {1}", "Timeout", _CurrentTaskDescription));
if (!abortedByUser) dlg_error.DoModal(GUIWindowManager.ActiveWindow);
}
}
}
// store info needed to invoke the result handler
bool stored_TaskSuccess = _CurrentTaskSuccess == true;
var stored_Handler = _CurrentResultHandler;
object stored_ResultObject = _CurrentResult;
// clear all fields and allow execution of another background task
// before actually executing the result handler -> this way a result handler can also inovke another background task)
_CurrentResultHandler = null;
_CurrentResult = null;
_CurrentTaskSuccess = null;
_CurrentError = null;
backgroundThread = null;
abortedByUser = false;
IsBusy = false;
timeoutTimer.Stop();
Monitor.Exit(this);
// execute the result handler
if (stored_Handler != null) stored_Handler.Invoke(stored_TaskSuccess, stored_ResultObject);
}
