Xamarin.Forms.NavigationProxy.PopAsync: System.ArgumentOutOfRangeException: Index was out of range - xamarin.ios

Question

I recently got that curious exception in my Xamarin App on iOS. I currently struggle to symbolicate it properly in HockeyApp but anyway here is the crash reporter log from HA:
Hardware Model: iPhone4,1
Process: trucker_rolspedi [625]
Path: /var/containers/Bundle/Application/B028371C-62B4-4BCD-8491-C78EFE825D22/trucker_rolspediOS.app/trucker_rolspediOS
Identifier: com.rolsped.TruckerApp
Version: 1.1 (60)
Code Type: ARM
Parent Process: ??? [1]
Date/Time: 2016-12-04T04:53:09Z
Launch Time: 2016-12-04T04:46:07Z
OS Version: iPhone OS 9.3.5 (13G36)
Report Version: 104-Xamarin
Exception Type: SIGABRT
Exception Codes: #0 at 0x21efec5c
Crashed Thread: 0
Application Specific Information:
*** Terminating app due to uncaught exception 'System.ArgumentOutOfRangeException', reason: 'System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.'
Xamarin Exception Stack:
Parameter name: index
at System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) <0x384df0 + 0x00040> in <15e850188d9f425bbeae90f0bbc51e17#ddbdd0f52c53581cb2d9c691bfe34183>:0
at System.ThrowHelper.ThrowArgumentOutOfRangeException () <0x384b68 + 0x0001b> in <15e850188d9f425bbeae90f0bbc51e17#ddbdd0f52c53581cb2d9c691bfe34183>:0
at System.Collections.Generic.List`1[T].get_Item (System.Int32 index) <0x24a68c + 0x0002f> in <15e850188d9f425bbeae90f0bbc51e17#ddbdd0f52c53581cb2d9c691bfe34183>:0
at Xamarin.Forms.NavigationProxy.Pop () <0x5678b4 + 0x00047> in <f9095492ed2b43559d0236ac22ab7223#ddbdd0f52c53581cb2d9c691bfe34183>:0
at Xamarin.Forms.NavigationProxy.OnPopAsync (System.Boolean animated) <0x567518 + 0x0005b> in <f9095492ed2b43559d0236ac22ab7223#ddbdd0f52c53581cb2d9c691bfe34183>:0
at Xamarin.Forms.NavigationProxy.PopAsync (System.Boolean animated) <0x56708c + 0x0002f> in <f9095492ed2b43559d0236ac22ab7223#ddbdd0f52c53581cb2d9c691bfe34183>:0
at trucker_rolsped.Pages.Media.TaskPhotoUploadPage+<SendMediaOnClicked>d__9.MoveNext () <0xe86944 + 0x013bf> in <3fbc044b4d76429b8dee1ec91e769c22#ddbdd0f52c53581cb2d9c691bfe34183>:0
Here the Code from the root cause Stacktrace line. It must happen at the await Navigation.PopAsync(animated: false)statement:
private async void SendMediaOnClicked(object sender, EventArgs e)
{
SendMedia.IsEnabled = false;
try
{
SelectedMedia.DokArt = _dokArt;
SelectedMedia.TruckAppId = _truckAppId;
UserDialogs.Instance.ShowLoading("Foto wird hochgeladen...");
await AzureBlobStorageManager.Instance.UploadMediaAsync(SelectedMedia);
UserDialogs.Instance.HideLoading();
switch (SelectedMedia.MediaState)
{
case MediaState.Uploaded:
if (IsTakenPhoto)
{
var result = await DisplayAlert("Foto Upload", "Foto wurde erfolgreich hochgeladen. Möchten Sie das Foto jetzt vom Handy löschen?", "Ja", "Nein");
if (result)
{
//Platform specific file delete
var truckerappMedia = SelectedMedia.File.Path;
var platformFileHandler = DependencyService.Get<IFileHandling>();
if (platformFileHandler != null)
if (await platformFileHandler.FileExistsAsync(truckerappMedia))
{
var deleted = await platformFileHandler.DeleteFileAsync(truckerappMedia);
if (deleted)
UserDialogs.Instance.Toast("Foto wurde erfolgreich hochgeladen und am Handy gelöscht!!", TimeSpan.FromSeconds(value: 2));
else
UserDialogs.Instance.Toast("Foto konnte nicht gelöscht werden! Falls Sie das Foto nicht benötigen " +
"bitte in der Fotogallery selbst löschen", TimeSpan.FromSeconds(value: 5));
}
}
}
else
UserDialogs.Instance.Toast("Upload erfolgreich!", TimeSpan.FromSeconds(value: 2));
break;
case MediaState.Queued:
UserDialogs.Instance.Toast("Upload erfolgt automatisch wenn Sie wieder mit Internet oder dem mobilem Netz verbunden sind!");
break;
case MediaState.Created:
await DisplayAlert("Media Info", "Upload MediaState.Created!", "Ok");
break;
case MediaState.Error:
await DisplayAlert("Media Info", "Upload MediaState.Error!", "Ok");
break;
default:
await DisplayAlert("Media Info", "Upload MediaState Unknown!", "Ok");
break;
}
}
catch (Exception ex)
{
SelectedMedia.MediaState = MediaState.Error;
await DisplayAlert("Sende Media Fehler", ex.Message, "Ok");
}
finally
{
if (SelectedMedia.MediaState == MediaState.Uploaded)
{
SelectedMedia?.Dispose();
SelectedMedia = null;
}
_workflowItem.TruckAuftragWorkFlow.TaskStatusId = 80;
await Navigation.PopAsync(animated: false);
_tcs.SetResult(true);
}
}
Here the 2 code areas where I instantiate and use the TakePhotoUploadPage:
1. Usage: From another page called Task40ActionPage
In **Task40ActionPage ** I invoke that method to show the TakePhotoUploadPage :
private async void RejectLoadInTimeClicked(object sender, EventArgs e)
{
_workflowItem.TruckAuftragLauf.FlagFotoLadezeit = null;
try
{
await ShowPhotoPageAsync(this, _workflowItem);
}
catch (Exception ex)
{
await MetricsManagerHelper.Instance.SendExceptionToApplicationInsights(ex);
}
await Navigation.PopAsync(animated: false);
_tcs.SetResult(true);
}
public async Task<bool> ShowPhotoPageAsync(Page page, WorkflowItem workflowItem)
{
TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
try
{
await Navigation.PushAsync(new TaskPhotoUploadPage(tcs, workflowItem, dokArt: "50"), animated: false);
}
catch (Exception e)
{
tcs.SetException(e);
}
return await tcs.Task;
}
2. Usage: From an ICommand Action delegate:
public async Task Task50ActionAsync(WorkflowItem workflowItem)
{
bool isLastWorkItem = false;
var page = Application.Current.MainPage.Navigation.NavigationStack.LastOrDefault();
try
{
if (workflowItem.QuestionYn)
{
if (page != null)
Device.BeginInvokeOnMainThread(
async () =>
{
try
{
bool isOk = await page.DisplayAlert("Todo Command", "Task50ActionAsync ausführen?", "Ja", "Nein");
if (isOk)
{
await ShowPhotoPageAsync(page, workflowItem, dokArt: "60");
UserDialogs.Instance.ShowLoading("Aufgabe wird gespeichert...", MaskType.Black);
isLastWorkItem = await InnerTask50ActionAsync(workflowItem);
//PUSH changes to remote.db
await OfflineSyncStoreManager.Instance.PushAsync(OfflineSyncStoreManager.Instance.TruckAuftragWorkFlowTable.TableName);
if (isLastWorkItem)
{
// Set TAL to completed
workflowItem.TruckAuftragLauf.IsCompleted = true;
// Pop Workflow UI View
Device.BeginInvokeOnMainThread(async () => await page.Navigation.PopAsync(animated: false));
}
UserDialogs.Instance.HideLoading();
}
}
catch (Exception e)
{
await MetricsManagerHelper.Instance.SendExceptionToApplicationInsights(e);
Device.BeginInvokeOnMainThread(
async () =>
{
await
page.DisplayAlert("Todo Command Error",
$"TaskId={workflowItem.TaskId} Action Error:{e}", "Ok");
});
}
});
}
else
{
await ShowPhotoPageAsync(page, workflowItem, dokArt: "60");
UserDialogs.Instance.ShowLoading("Aufgabe wird gespeichert...", MaskType.Black);
isLastWorkItem = await InnerTask50ActionAsync(workflowItem);
//PUSH changes to remote.db
await OfflineSyncStoreManager.Instance.PushAsync(OfflineSyncStoreManager.Instance.TruckAuftragWorkFlowTable.TableName);
if (isLastWorkItem)
{
// Set TAL to completed
workflowItem.TruckAuftragLauf.IsCompleted = true;
// Pop Workflow UI View
Device.BeginInvokeOnMainThread(async () => await page.Navigation.PopAsync(animated: false));
}
UserDialogs.Instance.HideLoading();
}
}
catch (Exception e)
{
await MetricsManagerHelper.Instance.SendExceptionToApplicationInsights(e);
if (page != null)
Device.BeginInvokeOnMainThread(
async () =>
{
await
page.DisplayAlert("Todo Command Error", $"TaskId={workflowItem.TaskId} Action Error:{e}",
"Ok");
});
}
}
public async Task<bool> ShowPhotoPageAsync(Page page, WorkflowItem workflowItem, string dokArt)
{
TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
try
{
await page.Navigation.PushAsync(new TaskPhotoUploadPage(tcs, workflowItem, dokArt: dokArt), animated: false);
}
catch (Exception e)
{
tcs.SetException(e);
}
return await tcs.Task;
}
Thanks to everyone with helpful suggestions in advance,
Eric

Answer 1

As Yuri S. suggested that code works to fix a NavigationStack PopAsync when the Stack is empty:
if (Navigation.NavigationStack.Count == 1)
{
await MetricsManagerHelper.Instance.SendErrorToApplicationInsightsAsync($"Navigationstack Count == 1");
}
else
{
await Navigation.PopAsync(animated: false);
}
Thanks for you great support!!!
Eric