Question

I’m looking at Apple’s example code from the ScrollViewSuite. I must be doing something wrong in comparison. In their RootViewController, they do:

- (void)loadView {
    [super loadView];

    // set the tag for the image view
    [imageView setTag:ZOOM_VIEW_TAG];

    // add gesture recognizers to the image view
    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];
    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
    UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];

    [doubleTap setNumberOfTapsRequired:2];
    [twoFingerTap setNumberOfTouchesRequired:2];

    [imageView addGestureRecognizer:singleTap];
    [imageView addGestureRecognizer:doubleTap];
    [imageView addGestureRecognizer:twoFingerTap];

    [singleTap release];
    [doubleTap release];
    [twoFingerTap release];

    // calculate minimum scale to perfectly fit image width, and begin at that scale
    float minimumScale = [imageScrollView frame].size.width  / [imageView frame].size.width;
    [imageScrollView setMinimumZoomScale:minimumScale];
    [imageScrollView setZoomScale:minimumScale];
}

In IB, they have their imageView as a subView of the imageScrollView. My .xib is set up the same way. I put this code in my viewDidLoad instead of loadView. I do not get any calls when I double tap on my imageView. I’m wondering why. Here is my version of what they did:

- (void)viewDidLoad {
    [self updateOnScreenImages];  // this is where my imageView.image property gets set

    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
    doubleTap.numberOfTapsRequired = 2;

    UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];
    [doubleTap setNumberOfTouchesRequired:2];


    [self.imageView addGestureRecognizer:doubleTap];
    [self.imageView addGestureRecognizer:twoFingerTap];

    [doubleTap release];
    [twoFingerTap release];

}

Is there something I am doing wrong compared to what Apple is doing? The logic seems pretty similar to me. But I’m not getting my callbacks when I double tap. I tried adding the gestures to the self.scrollView as well, but that doesn’t work either. Thoughts? Thanks!

Answer 1

Try to add:

   self.imageView.userInteractionEnabled = YES;

by default UIImageViews have that property set to NO
(apple may have changed it in XIB file, and you may have lost that…)