ios animation not working

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController {
}


@property (strong, nonatomic) IBOutlet UILabel *predictionLabel;
@property (strong, nonatomic) NSArray *predictionArray;
@property (strong, nonatomic) UIImageView *imageView;

-(void) makePrediction;

@end

viewcontroller.m:


#import "ViewController.h"

@implementation ViewController
@synthesize predictionLabel;
@synthesize predictionArray;
@synthesize imageView;

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIImage *image = [UIImage imageNamed:@"background.png"];
    self.imageView = [[UIImageView alloc]initWithImage:image];
    [self.view insertSubview:self.imageView aboveSubview:0];

    self.predictionArray = [[NSArray alloc] initWithObjects:@"It is certain",@"It is decidedly so",@"All signs say YES",
                                @"The stars are not aligned",
                                @"My reply is no",
                                @"It is doubtful",
                                @"Better not tell you now",
                                @"Concentrate and ask again",
                                @"Unable to answer now",@"Please stop bothering me",@"It is true",@"It is false", @"Really stop bothering me", nil];
    self.imageView.animationImages = [[NSArray alloc]initWithObjects:[UIImage imageNamed:@"cball00001"],[UIImage imageNamed:@"cball00002"],[UIImage imageNamed:@"cball00003"],[UIImage imageNamed:@"cball00004"],[UIImage imageNamed:@"cball00005"],[UIImage imageNamed:@"cball00006"],[UIImage imageNamed:@"cball00007"],[UIImage imageNamed:@"cball00008"],[UIImage imageNamed:@"cball00009"],[UIImage imageNamed:@"cball00010"],[UIImage imageNamed:@"cball00011"],[UIImage imageNamed:@"cball00012"],[UIImage imageNamed:@"cball00013"],[UIImage imageNamed:@"cball00014"],[UIImage imageNamed:@"cball00015"],[UIImage imageNamed:@"cball00016"],[UIImage imageNamed:@"cball00017"],[UIImage imageNamed:@"cball00018"],[UIImage imageNamed:@"cball00019"],[UIImage imageNamed:@"cball00020"],[UIImage imageNamed:@"cball00021"],[UIImage imageNamed:@"cball00022"],[UIImage imageNamed:@"cball00023"],[UIImage imageNamed:@"cball00024"], nil];
    self.imageView.animationDuration = 1.0;
    self.imageView.animationRepeatCount = 1;

}

- (void)viewDidUnload
{
    [self setPredictionLabel:nil];
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
}

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}


-(void) makePrediction {
    NSUInteger index = arc4random_uniform(self.predictionArray.count);
    self.predictionLabel.text = [self.predictionArray objectAtIndex:index];

    [self.imageView startAnimating];
}

-(BOOL) canBecomeFirstResponder{
    return YES;
}

- (void) motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event{

    self.predictionLabel.text = @"";

}

-(void) motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event{
    if (motion == UIEventSubtypeMotionShake){
        [self makePrediction];
    }
}

-(void) motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event{

    NSLog(@"Motion Cancelled");

}

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    self.predictionLabel.text = @"";

}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    [self makePrediction];


}


@end