Suddenly iOS App is not responsive at all - ios

Question

After I call a certain Google's Youtube library, my application suddenly becomes not responsive at all after one of its callback.
Not responsive means all UI components cannot be clicked.
Is there such thing in iOS that can disable entire screen to be not responsive at all?
The code:
self.uploadFileTicket = [service executeQuery:query
completionHandler:^(GTLServiceTicket *ticket,
GTLYouTubeVideo *uploadedVideo,
NSError *error) {
// Callback
_uploadFileTicket = nil;
if (error == nil) {
[_delegate videoUploadedSuccessfully:YES error:nil];
} else {
[_delegate videoUploadedSuccessfully:NO error:error.description];
}
}];
Inside my ViewController:
- (void)videoUploadedSuccessfully:(BOOL)success error:(NSString *)errorMessage{
dispatch_async(dispatch_get_main_queue(), ^{
if(success){
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Youtube"
message:#"Video uploaded successfully"
delegate:nil
cancelButtonTitle:nil
otherButtonTitles:#"OK", nil];
[alert show];
}
else{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Youtube"
message:errorMessage
delegate:nil
cancelButtonTitle:nil
otherButtonTitles:#"OK", nil];
[alert show];
}
});
}
Update
I have tried using Instrument and got following:
Does this mean my Working Thread are blocking Main Thread?

Answer 1

Finally I found the ROOT cause of this issue. There is somewhere in the code before uploading the video to Youtube:
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];

Answer 2

I cannot pin-point the issue. But, here are some of my suggestions.
The method call [service executeQuery:query completionHandler: has a completion handler. Therefore, it's mostly an async task. Therefore the task of the service should be done in a background thread and should not block the UI.
In case you're not sure whether the call is in the main thread, use the following LOC to clarify.
[NSThread isMainThread] will return true only if the executing thread is the main thread/ UI-thread.
Can you also put a NSLog at videoUploadedSuccessfully and check whether the delegate method gets called multiple times?
You do not need the block
dispatch_async(dispatch_get_main_queue(), ^{}
The delegate method should get executed on the main thread itself as long as you're calling the service-query method on the main thread.
Finally check whether you're calling the [service executeQuery:query method from the main thread?