我有以下代碼：System.Threading.Tasks.Task appointmentEndTask = App.ArdaBusinessLogic.AppointmentEnd(_appointment);System.Threading.Tasks.Task appointmentEndCompletedTask = appointmentEndTask.ContinueWith( async task => { _appointmentDetailPage.IsDirty = true; await App.MasterNavigationPage.Navigation.PopModalAsync(); }, System.Threading.CancellationToken.None, System.Threading.Tasks.TaskContinuationOptions.OnlyOnRanToCompletion, System.Threading.Tasks.TaskScheduler.FromCurrentSynchronizationContext());System.Threading.Tasks.Task appointmentEndFaultedTask = appointmentEndTask.ContinueWith( async task => { await App.MasterNavigationPage.Navigation.PopModalAsync(); await App.ShowErrorPageAsync(task.Exception); }, System.Threading.CancellationToken.None, System.Threading.Tasks.TaskContinuationOptions.OnlyOnFaulted, System.Threading.Tasks.TaskScheduler.FromCurrentSynchronizationContext());因此，如果“AppointmentEnd”任務完成，則應關閉當前模態頁面。有時（并非總是?。┪以诒罎⑷罩局惺盏揭韵洛e誤。在本例中，第 139 行是“_appointmentDetailPage.IsDirty = true”之后的“await App.MasterNavigationPage.Navigation.PopModalAsync()”。不幸的是，我不明白為什么會出現這個錯誤。你能幫助我嗎？
1 回答
慕斯709654
TA貢獻1840條經驗 獲得超5個贊
首先，為什么要使用如此復雜的語法而不是利用異步等待？
public async void EndAppointement()
{
try
{
await App.ArdaBusinessLogic.AppointmentEnd(_appointment);
_appointmentDetailPage.IsDirty = true;
await App.MasterNavigationPage.Navigation.PopModalAsync();
}
catch (Exception exception)
{
await App.MasterNavigationPage.Navigation.PopModalAsync();
await App.ShowErrorPageAsync(exception);
}
}
二、看XF源碼：
protected override async Task<Page> OnPopModal(bool animated)
{
Page modal = ModalStack[ModalStack.Count - 1];
if (_owner.OnModalPopping(modal))
{
_owner.OnPopCanceled();
return null;
}
Page result = await base.OnPopModal(animated);
result.Parent = null;
_owner.OnModalPopped(result);
return result;
}
您的模態堆棧似乎混亂了：這意味著您正在嘗試彈出不在堆棧上的頁面。您確定您處于模態頁面嗎？也許使用PopAsync而不是PopModalAsync.
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