Unable to change UIBarButtonItem - ios

Question

**Background** When my app loads a UINavigationController is programmatically added and given a leftBarButtonItem and a rightBarButtonItem. During launch a check is made to see if new data is required and if so a method is run to go and get new data from our web server. During this time, the rightBarButtonItem is changed to a UIActivityIndicatorView which will show a spinning activity indicator. When the data download is done, the rightBarButtonItem returns to a UIBarButtonItem. This works fine.
On another UIViewController I need to allow the user to manually get new data and send their data to us. During this time I need the rightBarButtonItem to change to a UIActivityIndicatorView as before. But when I try to do so, the data is downloaded ok but the rightBarButtonItem is never changed.
I think my problem may have something to do with me not being able to reference the UINavigationController and its navigationItems.
**Code** My first UIViewController's implementation where the rightBarButtonItem is changed:
-(void)statusIsLoading{
UIActivityIndicatorView *uiLoading = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
uiLoading.hidesWhenStopped = YES;
NSLog(#"Start animating");
[uiLoading startAnimating];
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:uiLoading];
}
-(void)statusFinishedLoading{
UIActivityIndicatorView *uiLoading = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
uiLoading.hidesWhenStopped = YES;
[uiLoading stopAnimating];
UIBarButtonItem *showSettingsButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:#"Settings.png"] style:UIBarButtonItemStylePlain target:self action:#selector(showSettings:)];
self.navigationItem.rightBarButtonItem = showSettingsButton;
}
**What I have tried** I have tried setting the self.navigationItem.rightBarButtonItem in the second UIViewController but this does nothing. I have also tried running the method that calls the above two methods from an instantiated class:
InitViewController *ivcInstance = [[InitViewController alloc] init];
[ivcInstance performUpdate];
This runs the 'performUpdate' code just fine, the 'performUpdate' method called the 'statusIsLoading' and 'statusFinishedLoading' methods but the rightBarButtonItem does not change.
I think there is something very simple I am missing here. Thanks.
**Edit** I have just tried checking for the current value of the rightBarButtonItem on the pageLoad of the second UIViewController and it appears to be nil:
UIBarButtonItem *newItem = self.navigationItem.rightBarButtonItem;
Here newItem = nil. Am I not targeting the correct navigationItem? should it be something other than 'self'?
**Edit 2**
In the second UIViewController I can alter the properties of the navigationBar:
[self.navigationController.navigationBar setBarTintColor:[UIColor colorWithRed:0.6 green:0.01 blue:0.36 alpha:2.0f]];
But if I try the same with the barButtonItem then nothing happens, why is this?
[self.navigationController.navigationItem setRightBarButtonItem:[[UIBarButtonItem alloc] initWithCustomView:uiLoading]];
same with:
[self.navigationItem setRightBarButtonItem:[[UIBarButtonItem alloc] initWithCustomView:uiLoading]];

Answer 1

In your statusFinishedLoading you have some unused codes like below
-(void)statusFinishedLoading
{
/*UIActivityIndicatorView *uiLoading = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
uiLoading.hidesWhenStopped = YES;
[uiLoading stopAnimating];*/ //These are unused codes.
UIBarButtonItem *showSettingsButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:#"Settings.png"] style:UIBarButtonItemStylePlain target:self action:#selector(showSettings:)];
self.navigationItem.rightBarButtonItem = showSettingsButton;
}
Also put NSLog in statusFinishedLoading methods and check whether this method called or not.
Thanks!

Answer 2

Try to set the rightBarButtonItem within a main-thread block. Once you have received the response, it should not block the UI.
-(void)statusFinishedLoading
{
UIActivityIndicatorView *uiLoading = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
uiLoading.hidesWhenStopped = YES;
[uiLoading stopAnimating];
UIBarButtonItem *showSettingsButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:#"Settings.png"] style:UIBarButtonItemStylePlain target:self action:#selector(showSettings:)];
//Use a block to set the rightBarButton.
dispatch_async(dispatch_get_main_queue(), ^{
self.navigationItem.rightBarButtonItem = showSettingsButton;
});
}
Hope this does the trick.
Edit : You need to create a UINavgationitem in the storyboard, connect the outlet to the .h file and call it statusNavigationItem then reference this navigationItem object to set the rightBarButton.