public override bool OnOptionsItemSelected(IMenuItem item) {
Android_Content.ContentResolver cr = GetActivity().GetContentResolver();
switch (item.GetItemId()) {
case POPULATE_ID:
if (mPopulatingTask != null) {
mPopulatingTask.Cancel(false);
}
mPopulatingTask = new PopulateAsyncTask(cr);
mPopulatingTask.Execute((object[]) null);
return true;
case CLEAR_ID:
if (mPopulatingTask != null) {
mPopulatingTask.Cancel(false);
mPopulatingTask = null;
}
AsyncTask<object, object, object> task = new ClearAsyncTask(cr);
task.Execute((object[])null);
return true;
default:
return base.OnOptionsItemSelected(item);
}
}
/// <summary>
/// 撤销任务
/// </summary>
private void Cancel()
{
if (task != null)
{
task.Cancel();
this.lsv.Items.Add("Task has been cancelled.");
}
}
private void Redraw(bool forceDraw)
{
if (forceDraw || _flinging)
{
Invalidate();
}
else
{
_renderTask?.Cancel(true);
_renderTask = PdfFile.GetPages(GetPageFromInclusive(_offSet.Y), GetPageToExclusive(_offSet.Y), _onPdfPageRenderListener);
}
}
/// <summary>
/// Handles the <see cref="IFolderSystemContext.SelectedItemsChanged"/> event.
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
private void SelectedItemsChangedEventHandler(object sender, EventArgs args)
{
if (_operationEnablementTask == null)
{
return;
}
// cancel any previous operation enablement queries
_operationEnablementTask.Cancel();
// if selection is empty, there is no need to query operation enablement
if (this.Selection.Equals(Desktop.Selection.Empty))
{
_workflowEnablement = null;
EventsHelper.Fire(_selectedItemsChanged, this, EventArgs.Empty);
return;
}
// query for operation enablement asynchronously
IDictionary <string, bool> enablement = null;
_operationEnablementTask.Run(
delegate
{
enablement = QueryOperationEnablement(this.Selection);
},
delegate
{
_workflowEnablement = enablement;
EventsHelper.Fire(_selectedItemsChanged, this, EventArgs.Empty);
},
delegate(Exception e)
{
Platform.Log(LogLevel.Error, e);
// still need to fire the event, so that enablement of tools is updated
EventsHelper.Fire(_selectedItemsChanged, this, EventArgs.Empty);
});
}
static void LogErrorAndCancel(AsyncTask asyncTask, Exception exc)
{
asyncTask.LogCodedError("XA0000", Properties.Resources.XA0000_Exception, exc);
asyncTask.Cancel();
}
