detect a touch down event on UIImageView(s)

Question

I placed 4 UIImageView on UIView and I named them

UIImageView myImg1 = [[UIImageView alloc] init];     
UIImageView myImg2 = [[UIImageView alloc] init];             


        

Answer 1

A stylish solution is to use the UIGestureRecognizer object:

in your loadView method (or anywhere you code the UIImageView(s) drawing...):

   UITapGestureRecognizer *tapRecognizer;
    UIImageView *anImageView = [[UIImageView alloc] initWithFrame:CGRectMake(20, 20, 100, 100)];
    [anImageView setTag:0]; //Pay attention here!, Tag is used to distinguish between your UIImageView on the selector
    [anImageView setBackgroundColor:[UIColor redColor]];
    [anImageView setUserInteractionEnabled:TRUE];
    tapRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageViewDidTapped:)] autorelease];
    tapRecognizer.numberOfTapsRequired = 1;
    [anImageView addGestureRecognizer:tapRecognizer];
    [contentView addSubview:anImageView];
    [anImageView release];

    UIImageView *anotherImageView = [[UIImageView alloc] initWithFrame:CGRectMake(80, 180, 100, 100)];
    [anotherImageView setTag:1]; //Pay attention here!, Tag is used to distinguish between your UIImageView on the selector
    [anotherImageView setBackgroundColor:[UIColor greenColor]];
    [anotherImageView setUserInteractionEnabled:TRUE];
    tapRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(imageViewDidTapped:)] autorelease];
    tapRecognizer.numberOfTapsRequired = 1;
    [anotherImageView addGestureRecognizer:tapRecognizer];
    [contentView addSubview:anotherImageView];
    [anotherImageView release];

This is a simple imageViewDidTapped: sample method that you can use to distinguish between the two sample UIImageView objects above:

- (void)imageViewDidTapped:(UIGestureRecognizer *)aGesture {
    UITapGestureRecognizer *tapGesture = (UITapGestureRecognizer *)aGesture;

    UIImageView *tappedImageView = (UIImageView *)[tapGesture view];

    switch (tappedImageView.tag) {
        case 0:
            NSLog(@"UIImageView 1 was tapped");
            break;
        case 1:
            NSLog(@"UIImageView 2 was tapped");
            break;
        default:
            break;
    }
}