CODEWITHSUNDEEP
iosobjective-cuiviewcontroller
Asi Givati
Asi Givati

Reputation: 1475

Objective c - Detect current view from appDelegate

I'm using modal segue (without navigation controller) to move between viewController A and viewController B like so:

viewA *first = [self.storyboard instantiateViewControllerWithIdentifier:@"viewA"];
[self presentViewController:first animated:YES completion:nil];

And to move back : 

 [self dismissViewControllerAnimated:YES completion:nil];

Now, I want to know from the AppDelegate whether A or B is the current view right now. The problem is when I'm checking

[(AppDelegate *)[[UIApplication sharedApplication] delegate] window]

the answer is always view A - the first one.

I've tried to set the current view every time I'm using modal segue like so:

viewA *first = [self.storyboard instantiateViewControllerWithIdentifier:@"viewA"];
    [self presentViewController:first animated:YES completion:^
{
[[(AppDelegate *)[[UIApplication sharedApplication] delegate] window] setRootViewController:first];
}];

But it cause a few bugs (like unable to use "dismissViewControllerAnimated"),and it's impossible to work like that in every segue in a big project with many segues.

How should I work with that? And how should I detect the current view in more appropriate way?

Upvotes: 1

Views: 907

Answers (2)

michaelsnowden
michaelsnowden

Reputation: 6202

As was answered here

UIWindow *topWindow = [[[UIApplication sharedApplication].windows sortedArrayUsingComparator:^NSComparisonResult(UIWindow *win1, UIWindow *win2) {
    return win1.windowLevel - win2.windowLevel;
}] lastObject];

UIView *topView = [[topWindow subviews] lastObject];

However, doing this logic here sounds like bad architecture. What is the reason for you needing to know which view is currently presented inside of your AppDelegate?

Edit It seems like you want to respond to the applicationWillResignActive event from your view controller. Use something like this in the your game view controller.

- (void) applicationWillResign {
    NSLog(@"About to lose focus");
}

-(void) viewDidLoad {
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(applicationWillResign)
     name:UIApplicationWillResignActiveNotification
     object:NULL];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    [[NSNotificationCenter defaultCenter]
     removeObserver:self];
}

Upvotes: 1

danh
danh

Reputation: 62686

The appDelegate's window won't be equal to either view controller (viewControllerA or viewControllerB). You can ask the window for it's root view controller...

AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;

if (appDelegate.window.rootViewController == viewControllerA) {
    // always true if you always start the app with viewControllerA

... and you can ask any view controller for the view controller it presented...

if (appDelegate.window.rootViewController.presentedViewController == viewControllerB) {
   // will be true if viewControllerA has presented viewControllerB

But this is a tricky game. If, for example, viewControllerB presents some other viewControllerC, the condition above will continue to be true.

See the @Eric answer here (not the accepted answer) for a way to find the topmost vc in general.

Upvotes: 0

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