Resetting UIPageControl Resets View To Original State - objective-c

Question

I have an iPad view that has a ScrollView, and below that I'm using a Page Control Object to show what page it is on. Elsewhere on the screen, I have a timeline between say 12:00 AM and 5:00 AM - as time progresses, there is a UIImage that gets wider on top of the timeline to indicate the time of day. The UIImage gets wider as the day goes on through the use of an NSTimer that kicks off every minute or so.
In addition, I have 3 buttons on the page that will refresh the Scrollview with a new set of images inside of it. The number of images can be varied, anywhere between 3 and 7. So, when a button is pressed, I update the scrollview, and also update the Page Control object to set the "numberOfPages" property to the appropriate number.
OK, so the problem seems to be that whenever I click a button and the pageControl numberOfPages is changed, the UIImage reverts back to whatever size it was back when I originally designed it in Interface Builder (the storyboard).
I created a simplified example project that hopefully has enough to recreate the behavior...
ViewController.h:
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIButton *btnTest;
#property (weak, nonatomic) IBOutlet UIImageView *imgTest;
#property (weak, nonatomic) IBOutlet UIPageControl *pageControl;
- (IBAction)buttonPress:(id)sender;
#end
ViewController.m:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize imgTest,btnTest,pageControl;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
// Set up an observer to handle updating the timeline
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(UpdateWidth:)
name:#"UpdateWidth" object:nil];
}
-(void)viewDidAppear:(BOOL)animated {
// Send an updateTimeIndicator notification when screen loads.
[[NSNotificationCenter defaultCenter] postNotificationName:#"UpdateWidth" object:#"sent"];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)buttonPress:(id)sender {
pageControl.numberOfPages = 7;
pageControl.currentPage = 0;
}
-(void)UpdateWidth:(NSNotification *)notification{
[imgTest setFrame:CGRectMake([imgTest frame].origin.x, [imgTest frame].origin.y,
450, [imgTest bounds].size.height)];
imgTest.contentMode = UIViewContentModeScaleAspectFit; // This determines position of image
imgTest.clipsToBounds = YES;
[imgTest setNeedsDisplay];
NSLog(#"Width Updated");
}
#end
So, in this example, I have just 3 objects in the Window - the PageControl, a Button, and a UIImage that has the background set to blue. I'm using the Notification Center to send messages as to when to resize the UIImage (in this case, I'm only doing it once, when the view appears). The updateWidth routine sizes the UIImage to be 450 pixels wide, and the view appears as it should.
However, tapping the button will change the numberOfPages value, and in so doing, sets the UIImageView back to the size that it was when it was originally laid out in Interface Builder.
I do have a zipped project file if anyone would like to see it. Also, I did try this without using the Notification Center and the results were the same (I originally wasn't using the Notification Center, just thought it might give different results).
I can probably get by without using the PageControl object, but I'm now very curious as to why happens. Thanks!

Answer 1

I seem to have solved the problem by placing both the ScrollView and the PageControl objects into their own (new) UIView. To do this, I opened the storyboard in interface builder, drug a View object from the toolbox out to the interface window, and then placed both the existing ScrollView and the PageControl objects into the new UIView. Afterwards, changing the numberOfPages property of the PageControl did not affect anything else on the window.
I'm still confused as to this behavior though. I'm guess that because once the page control was placed in a new view and the problem stopped, that the PageControl wants to update the entire view that it is in when the numberOfPages property is changed.