I was in the middle of developing an update to my Xamarin Forms app, but when I debugged it on my iPhone, it crashed immediately on startup with the following message:
Assertion failure in -[UIApplication_runWithMainScene:transitionContext:completion:], /BuildRoot/Library/Caches/com/apple.xbs/Source/UIKit/UIKit-3600.5.2/UIApplication.m:3679
It was previously working fine, but now I can't run the app on my phone anymore without this crash. I have rebuilt several times and deployed from different computers, but nothing helps. How do I fix this issue?
Edit:
Before this started occurring, I had made some additions to the code. Unfortunately, after removing all of my changes, this issue is still plaguing further development. Any help or resource that might lead me to a solution will be greatly appreciated.
After some deep searching, it turns out that I mistakenly removed a part of my Application's constructor that initialized the MainPage. As a result, MainPage remained null. The framework probably tried to call a method or access a property without checking if the reference was null, causing the error. I'm not sure how long that mistake has been there.
This can also happen if you are not quick to launch a view. Avoid calling APIs or other lengthy processes before a page is displayed for the first time. You may do that in parallel but not in the same thread that launches the page.
Related
I've got a very bizarre situation. It appears that, when I load a webpage to my browser,
multiple threads (at least 2) are starting up. The app loads and runs fine on a
Windows XP box, but when I try to run it on my Windows 8 laptop it would seem that
more than one startup event is taking place and causing all kinds of collisions. This
is happening with both Firefox and IE.
To verify this behaviour, I placed a static int within a class, checked it to see if its
value is greater than zero, throw an exception if it is, then increment the int.
Of course, the exception is thrown.
What's very weird about this is that there is no multi-threading/multi-tasking involved
within my app.
When I "touch" the DLL for the webpage (rebuild it), it renders the webpage properly,
but the source for the webpage ("right click" > "View Page Source") has the source
for the unhandled exception webpage, with the message for the exception that my code
throws when the thread count is greater than zero.
I've tried creating a new project, then linking the code to it (Add Item ... Ad As Link),
then building it. It didn't do any good.
The Win XP system has IIS 6 with .NET 4.0, and the Win 8 laptop has IIS 7 with .NET 4.0.
Language is C#.
The truth is that I'm pretty much clueless about IIS.
I hope someone smarter than I am (which isn't saying much) has an idea as to what
is going on.
It appears that, when I load a webpage to my browser, multiple threads (at least 2) are starting up
Maybe onetime initializations. I doubt that every request causes an additional two threads to stay around.
it would seem that more than one startup event is taking place
That's normal This event fires for each instance of HttpApplication being created. This is basically a design error in ASP.NET. They thought that pooling HttpApplication instances and assigning one of them for each request was a good idea. It would have been better to have a singleton per AppDomain. Write this yourself. Like that:
class MyGlobalAppState { ... }
static Lazy<MyGlobalAppState> state = new Lazy<...>(StateFactory);
Be aware, that Lazy<T> stores any exception and just rethrows it. This causes your app to be permanently broken in case StateFactory throws. It will never recover without pool restart. This is a design error in Lazy<T>. Find a way to deal with that.
but the source for the webpage ("right click" > "View Page Source") has the source for the unhandled exception webpage
Some browsers re-GET the page to view the source. This can be annoying or handy.
It is hard to tell what is causing this behavior but as others suggested try to use Fiddler or any other http tracing tool to see what requests are sent.
Also, Win XP should be running IIS5.x while Win8 should be running IIS8.
By default IIS8 AppPool should be running with the integrated pipeline, which may behave differently. I would try changing the AppPool to use the Classic pipeline to see if it makes a difference.
I recently posted about a bug in MonoMac in which the window would abruptly disappear after clicking on a button 20 times or so. That bug, it turned out, doesn't seem to affect Xamarin.Mac, so I switched my project to that.
But now I'm seeing virtually the same bug in a different context: after typing a few lines of text into an NSTextField, the window disappears in exactly the same manner. No error, no exception; it just vanishes. Poof, gone!
I've reproduced this in a trivial project: you can see it yourself by creating a new empty Xamarin.Mac project, adding this code in a new file, and running. Then mash the keyboard a little while. After 5 or 6 lines, the window disappears.
(Note that the app menus continue to work, writing log messages and executing my code when I select the menu commands. So it doesn't appear as though the app itself has crashed.)
Curiously, this seems to only occur when the field is inside an NSView subclass where IsFlipped has been overridden. But it doesn't matter whether IsFlipped returns true or false -- if the method is there at all, the bug occurs; if commented out, the bug does not seem to occur.
So: Has anyone else run into this sort of bug in Xamarin.Mac? Perhaps in other contexts that will give us more clues as to a root cause? Any debugging tips for a Xamarin newbie?
(I know I could work around it in some projects by avoiding IsFlipped, but I worry that it would just pop up to bite me in some other way.)
OK, it turns out that this isn't a bug in Xamarin.Mac at all, but in my code. Because I wasn't retaining a reference to the NSWindow object, it went out of scope, and as soon as the garbage collector gets around to noticing it, it's disposed and the GUI window is torn down.
All we have to do is retain a reference to the window (for example, in the AppDelegate class), and the problem goes away.
Hats off to Chris Hamons at Xamarin, who jumped right on this and quickly found the problem for me.
It looks like a duplicate, but believe I checked other answers, nothing worked.
My application started crashing while closing the application with below error. It was working properly few days back, some recent changes is causing the issue. And one this starts on a machine, even though I replace with previous working DLL, still the issue comes.
Microsoft Visual C++ Runtime Library
Runtime Error!
Program:C:\DigiMic\...
This application has requested the Runtime to terminate it in an unusual way...
This pop-up comes for 1 second with OK button, then automatically closes. The main problem is it happens while shutting down my application.
My Application: It is a WPF, C# application which uses Matlab used business DLL for few functionality. The application works fine while using the Matlab used DLL and its function, only crashes while exiting the WPF.
I tried to Wrap the App.Current.ShutDown with try..catch... but the it never hits catch orfinally block. Then I also tried AppDomain.Current.UnHandledException += new..., it still does not hit the function on exception.
The other problem is, I am not able to see the complete path of the exe that causes this exception.
Question:
Is there a way, I can suppress this error?
Where is this error gets logged in windows?I tried to look into Event Viewer, but nothing is there.
Is there any workaround? Since it's software delivery time for the product. :(
We are currently trying to incorporate Lync communication (Lync SDK 2010) into our application and we have run into an issue with the VideoWindows (CaptureVideoWindow, RenderVideoWindow) of the AVModality's VideoChannel: They are always null, even after successfully calling BeginStart. The connection is definitely established. We can talk. Our own video is shown in a remote Lync client. AVModalityState is Connected. VideoChannelState goes from Connecting to Receive to Send.
It does not matter when and how we try to access them: Directly after BeginStart, in the AsyncCallback of BeginStart, in response to various state changes or in response to an external trigger (user click event); in the main/UI thread or in an event/callback thread. The two video windows are always null.
In the example application "%PROGRAMFILES%\Microsoft Lync\SDK\Samples\AudioVideoConversation", everything works as intended: As soon as BeginStart has finished, we can access the non-null video windows. In our little stand-alone prototype project, it works, too. But in our real application, it does not.
We have double checked everything and we have really run out of ideas of what might cause this problem.
Any ideas, any hints? Anything that we should be aware of?
(Link to corresponding MSDN forum thread)
Update (4th July 2012, 15:46 CET):
When we take a look at the members of the VideoChannel we find that internally a COMException occured in "Microsoft.Office.Uc": Error loading DLL, HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY). More details in the attached screenshot.
We did some research on this error, but found nothing that worked for us. Any ideas what causes the Exception?
Update (9th July 2012, 16:43 CET):
We did some further testing...
Our software consists of one main application and many plugin-like "apps" loaded via MEF. We created a minimal test app that makes a video call: The video windows did not work (as expected). But when we took the identical code and created a separate solution outside of our architecture, then it did work. So, it was an issue with the environment, not the code.
At first, we suspected MEF might be the problem. So, we hacked the lync code into our main application - circumventing the whole app architecture. Still not working.
Then we sliced off our whole system, bit by bit, until we finally reached a point where it did work. After following wrong tracks several times, we finally found the culprit... Quartz.NET!
For some strange reason the mere presence of an assembly reference to the Quartz.dll v.1.0.3.3, even without a single line of Quartz code, causes the video windows to not work. Unbelievable, but it's 100% reproducible: If we take the previously mentioned test solution and do nothing but add the reference, it stops working.
Any idea how such a thing is possible?
We solved it! Kind of. A reference to a Quartz.NET DLL somehow caused the issue. More details in the updated question.
For now, we have removed the component that used Quartz. We currently do not need it.
But I'm still interested in further input how a mere reference can cause such an issue.
I've been writing an app using the awesome new Razor view engine and for the most part, things have been great.
One issue I keep running into, however, is that if I should happen to write invalid code, such as referencing a null property or even a non existent property, rather than throwing an error, something happens in the background that causes the browser to wait and wait and wait and if I do not cancel the browser's request quick enough, IIS will simply hang.
It seems as if it enters some sort of loop. CPU usage goes up (though not terribly high) and restarting IIS via either GUI or iisreset command seems to take abnormally long (presumably while it waits for the process to safely shutdown).
This also happens for other invalid code scenarios such as failing to close a code block with a closing brace.
I notice this behavior on more than one machine.
Any ideas if this is a known issue or have I mis configured something?
Thanks!
I found the problem. I had installed a package via NuGet called "Razor Debugger" and apparently this plugin was intercepting Razor errors somehow, and was consequently not showing them.
Removing that package now allows Razor to work properly. What a relief.
Steer clear of this library.