Proper way to unwind to HomeViewController?? Unbalanced Errors
I have an app and I have been struggling with apparent bad tutorials and was tore a new one on a previous thread so kinda apprehensive to post again. Sorry I learn by doing always have always will.
Anyway My login, Registration and other functionality is working perfectly. I am just having a rough time with the Barcode scan using AVFoundation. I setup my flow to go
(source: leaguelaunch.com)
Button Click on HomeViewController to Segue to BarcodeViewController after scan it pushes to the ScanResultsViewController.
ScanResultsViewController is going to send JSON post data and render the response but I have nothing in here yet due to the errors Im getting. All I have in here is this code to Unwind directly to the HomeViewController instead of having to Push Back (BarcodeView) then Back (HomeView)
- (void)viewDidLoad
{
[super viewDidLoad];
UIBarButtonItem *item = [[UIBarButtonItem alloc] initWithTitle:@"Back" style:UIBarButtonItemStyleBordered target:self action:@selector(back)];
self.navigationItem.hidesBackButton = YES;
self.navigationItem.leftBarButtonItem = item;
NSLog(@"Made it to Success!!!");
}
-(void)back{
[self performSegueWithIdentifier:@"unwindToHomeResult" sender:self];
}
As you can see it will work but it could work once or it could work 10 times before I get the error.
2014-05-25 12:11:32.378 selfcheckin[3344:60b] QR Code = {"stop_id":"3","event_id":"1"}
2014-05-25 12:11:32.801 selfcheckin[3344:60b] StopReading Called
2014-05-25 12:11:32.812 selfcheckin[3344:60b] Made it to Success!!!
2014-05-25 12:11:42.615 selfcheckin[3344:60b] QR Code = {"stop_id":"3","event_id":"1"}
2014-05-25 12:11:43.322 selfcheckin[3344:60b] StopReading Called
2014-05-25 12:11:43.334 selfcheckin[3344:60b] Made it to Success!!!
2014-05-25 12:11:50.850 selfcheckin[3344:60b] QR Code = {"stop_id":"3","event_id":"1"}
2014-05-25 12:11:51.296 selfcheckin[3344:60b] StopReading Called
2014-05-25 12:11:51.308 selfcheckin[3344:60b] Made it to Success!!!
2014-05-25 12:11:51.349 selfcheckin[3344:60b] QR Code = {"stop_id":"3","event_id":"1"}
2014-05-25 12:11:51.352 selfcheckin[3344:60b] StopReading Called
2014-05-25 12:11:51.370 selfcheckin[3344:60b] nested push animation can result in corrupted navigation bar
2014-05-25 12:11:51.759 selfcheckin[3344:60b] Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted.
2014-05-25 12:11:51.851 selfcheckin[3344:60b] Unbalanced calls to begin/end appearance transitions for <ScanResultsViewController: 0x14e86570>.
So my main question is How to I get back from the ResultsView to the HomeView. Im tempted to just nix the NavigationController and see if I can do without. Any pointers on where I may be going wrong or the proper way to do this
Thx
It appears you are pushing two ScanResultsViewControllers onto the navigation stack at roughly the same time, which would corrupt the navigation bar and cause unwind segues to break.
I bet the reason that that is happening is because your BarcodeViewController is scanning for barcodes/QR-codes but does not stop scanning once one is found. Make sure to stop scanning for barcodes (or set a flag at least) when you successfully find one to make sure you only push one ScanResultsViewController.
I had this same exact problem happen to me when I implemented a QR-code scanner in one of my apps a while back. The following method would get called if a barcode/QR-code was found (I was using ZXingObjC, just FYI); you probably have a similar method in your BarcodeViewController:
- (void)captureResult:(ZXCapture *)capture result:(ZXResult *)result
{
if (result) {
[self performSegueWithIdentifier:@"ScanResults"];
}
}
The problem here is that this method can get called again even after the call to perform the segue, which means I was sometimes performing the segue twice. To stop this, I effectively stopped this by simply remembering that I had already found a barcode with something like this:
- (void)captureResult:(ZXCapture *)capture result:(ZXResult *)result
{
if (result && !self.foundBarcode) {
self.foundBarcode = YES;
[self performSegueWithIdentifier:@"ScanResults"];
}
}
... which prevented the segue from being performed twice. I imagine your scenario is probably pretty similar.