// Cria um botão que ativa o Indicator
CGRect frame = CGRectMake(0.0, 0.0, 25.0, 25.0);
self.activityIndicator = [[UIActivityIndicatorView alloc]
            initWithFrame:frame];
[self.activityIndicator sizeToFit];
self.activityIndicator.autoresizingMask =
    (UIViewAutoresizingFlexibleLeftMargin |
	UIViewAutoresizingFlexibleRightMargin |
	UIViewAutoresizingFlexibleTopMargin |
	UIViewAutoresizingFlexibleBottomMargin);

UIBarButtonItem *loadingView = [[UIBarButtonItem alloc]
         initWithCustomView:self.activityIndicator];
loadingView.target = self;
self.navigationItem.rightBarButtonItem = loadingView;