Swipe gesture detected but no image is displayed (UISwipeGestureRecognizer, UIImageView and NSArray)

Question

I am trying to swipe between 2 images. The gesture is recognized but no image is displayed.

I am attempting to do it programmatically. At first I am creating an UIImageView that I have declared in the .h file. That image view is called imageView.

In the .m file I am implementing that view. I have also added Swipe left and right gesture recognizers. The swipes trigger an action called handleSwipe. I know that the swipes are recognized because of an NSLog statement that is shown in my output log when a swipe occurs.

The handleSwipe action get an image from an NSArray and displays it based on whether we swipe left or right. That method put the image in imageView.

The problem I have is that I have is that handleSwipe does not display any image.

My code is below:

@implementation firstStartViewController
@synthesize imageView;
int imageIndex = 1;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    // Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.view.backgroundColor = [UIColor whiteColor];


imageView.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), CGRectGetHeight(self.view.bounds));

imageView.center = CGPointMake(CGRectGetWidth(self.view.bounds)/2.0f, CGRectGetHeight(self.view.bounds)/2.0f + 75);

imageView.userInteractionEnabled = YES;

[self.view addSubview:imageView];



UISwipeGestureRecognizer *swipeleft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
swipeleft.direction = UISwipeGestureRecognizerDirectionLeft;
[self.view addGestureRecognizer:swipeleft];



UISwipeGestureRecognizer *swiperight = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
swiperight.direction = UISwipeGestureRecognizerDirectionRight;
[self.view addGestureRecognizer:swiperight];


UIBarButtonItem *dismiss_btn = [[UIBarButtonItem alloc] initWithTitle:@"Start App" style:UIBarButtonItemStylePlain target:self action:@selector(dismissModal:)];

self.navigationItem.rightBarButtonItems = [NSMutableArray arrayWithObjects:dismiss_btn, nil];
}


- (IBAction)handleSwipe:(UIGestureRecognizer *)sender {

NSLog( @"Swiped");


NSArray *images=[[NSArray alloc] initWithObjects:
                 @"image1.png",
                 @"image2.png", nil];

UISwipeGestureRecognizerDirection direction = [(UISwipeGestureRecognizer *) sender direction];

switch (direction) {
    case UISwipeGestureRecognizerDirectionLeft:
        imageIndex++;
        break;
    case UISwipeGestureRecognizerDirectionRight:
        imageIndex--;
        break;
    default:
        break;
}
imageIndex = (imageIndex < 0) ? ([images count] -1): imageIndex % [images count];
imageView.image = [UIImage imageNamed:[images objectAtIndex:imageIndex]];
}

Answer 1

You should set your imageIndex to default value (Maybe 0) in your viewDidLoad method.

Just add this line in viewDidLoad.

imageIndex = 0;