[ObjC] Custom UIImageVIew with touchesEnded works only with the first view

Question

Hi! Sorry for bad title :(

I've a controller that has a scrollview where I display some other views, in this case an IngredientImage, that is a subclass of uiimageview:

#import "IngredientImage.h"

@implementation IngredientImage    

- (id) initWithImage:(UIImage *)image {
    if (self = [super initWithImage:image]) {

    }
    [self setUserInteractionEnabled:YES];
    return self;
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint location = [[touches anyObject] locationInView:self];

    if (CGRectContainsPoint([self frame], location)) {
         NSLog(@"This works...");   
    }
}

- (void)dealloc {
    [super dealloc];
}


@end

and there is the code that puts the views in the scrollview

- (void)viewDidLoad {
    [super viewDidLoad];
    [self addIngredients];

}

- (void)addIngredients {
    NSUInteger i;
    for (i = 1; i <= 10; i++) {
        UIImage *image = [UIImage imageNamed:@"ing.png"];
        IngredientImage *imageView = [[IngredientImage alloc] initWithImage:image];

        // setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
        CGRect rect = imageView.frame;
        rect.size.height = 50;
        rect.size.width = 50;
        imageView.frame = rect;
        imageView.tag = i;  // tag our images for later use when we place them in serial fashion
        [ingredientsView addSubview:imageView];
        [imageView release];
        [image release];
    }

    UIImageView *view = nil;
    NSArray *subviews = [ingredientsView subviews];

    // reposition all image subviews in a horizontal serial fashion
    CGFloat curYLoc = INGREDIENT_PADDING;
    for (view in subviews) {
        if ([view isKindOfClass:[IngredientImage class]] && view.tag > 0) {
            CGRect frame = view.frame;
            frame.origin = CGPointMake(INGREDIENT_PADDING, curYLoc);
            view.frame = frame;

            curYLoc += (INGREDIENT_PADDING + INGREDIENT_HEIGHT);
        }
    }

    // set the content size so it can be scrollable
    [ingredientsView setContentSize:CGSizeMake([ingredientsView bounds].size.width, (10 * (INGREDIENT_PADDING + INGREDIENT_HEIGHT)))];
}

the problem is that only the first view handles the touch event, and I don't know why :(

Can you help me?

Thanks

Answer 1

When you call

CGPoint location = [[touches anyObject] locationInView:self];

you are setting location with respect to the bounds of your imageView. But then in your if statement,

if (CGRectContainsPoint([self frame], location))

you are asking if the location is within your frame. But frame and bounds are different. Frame gives coordinates relative to your superview; bounds gives it relative to the view itself.

To fix this, change your if statement to read

if (CGRectContainsPoint([self bounds], location))

Now you are consistently using the same coordinate system in both calls, and your problem should go away.