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iOS Build a Photo Browser iPhone App Connecting to an API using OAuth Introducing API and OAuth 2.0

PhotoBomber[3396:53988] Unbalanced calls to begin/end appearance transitions for <UINavigationController: 0x79a868c0>.

I receive this log message when I run the application. I believe it is because of instagram login view being called in the UIColloectionViewController. It does not make the application crash. However, I would like to know if there is any enhancement to solve this issue.

7 Answers

Evan David
Evan David
4,296 Points

I was experiencing the same issue, which was a strange side effect of having no network connectivity in the simulator. I reset the content and settings on the simulator which at least temporarily 'resolved' the issue.

Chris McKnight
Chris McKnight
11,045 Points

This can happen for a few different reasons. Most of the time it is because you are animating 2 things at the same time. I have seen this happen when calling popToViewControllerAnimated: twice with both calls passing in YES. Another time this will occur is when you try to present a view controller from the view controller.

Thanks Chris, I believe my problem is related with presenting a view controller from the view controller. Is there any way to solve this problem?

Chris McKnight
Chris McKnight
11,045 Points

Yes, can you post some relevant code?

Chris! I'm having the same problem with my code. Is there any thing you could do to help me?

'''ObjectiveC

-(void)viewDidLoad { [super viewDidLoad];

self.title = @"#PhotoBomb";

[self.collectionView registerClass:[THPhotoCell class] forCellWithReuseIdentifier:@"photo"];
self.collectionView.backgroundColor = [UIColor whiteColor];

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
self.accessToken = [userDefaults objectForKey:@"accessToken"];

if (self.accessToken == nil) {

    [SimpleAuth authorize:@"instagram" completion:^(NSDictionary *responseObject, NSError *error) {
        NSString *accessToken = responseObject[@"credintials"][@"token"];
        [userDefaults setObject:accessToken forKey:@"accessToken"];
        [userDefaults synchronize];
    }];

} else {
    NSURLSession *session = [NSURLSession sharedSession];
    NSString *urlString = [[NSString alloc] initWithFormat:@"https://api.instagram.com/v1/tags/photobomb/media/recent?access_token=%@",self.accessToken];
    NSURL *url = [[NSURL alloc] initWithString:urlString];
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
    NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
            NSString *text = [[NSString alloc]initWithContentsOfURL:location encoding:NSUTF8StringEncoding error:nil];
            NSLog(@"text: %@", text);
    }];

    [task resume];
}

}

'''

Chris McKnight
Chris McKnight
11,045 Points

Move your code into viewDidAppear and the warning should go away. The problem with viewDidLoad is that the UINavigationController hasn't finished its animation yet. So, the navigation controller's animation is still happening when the modal's animation happens.

Moving the code to viewDidAppear puts the modal view animation into a continuous loop. The simulator presents the modal view and then dismisses it over and over.

Chris McKnight
Chris McKnight
11,045 Points

You're absolutely right. viewWillAppear and viewDidAppear are going to fire every time the modal opens and closes. It seems like the following are the only solutions:

  1. Disable the animation on the modal
  2. Wait until the navigation controller has finished its animation
  3. Move the code into a new method and call the method after a delay

Which do you think would be the best implement in this scenario and how would you do so? I'm only half a year into coding so I'm pretty new to this. Thank you so much for all your help!

Chris McKnight
Chris McKnight
11,045 Points

I think the best is to show the modal after the animation has finished otherwise the UI might change abruptly.

James Lin
James Lin
4,601 Points

I have a hacky solution to resolve this issue:

set a global: BOOL firstLoad;

in viewDidLoad: firstLoad = YES;

move the entire oAuth code to viewDidAppear and put int a if(firstLoad) { //oauth code}. after it is complete set firstLoad = NO;

This will ensure that the it executes when the navigation controller has finished animating, but only executes the oAuth stuff once