Why can I not receive touch events within my custom UIScrollView subclass?

Question

i have an uiscrollview with a uiimageview inside. I subclass the uiscrollview but i can not get touches to work touchbegin does not called. What should i do to call uitouch event?

what is wrong?

.h

#import <UIKit/UIKit.h>

@interface myScrollView : UIScrollView {

}

@end

.m

#import "myScrollView.h"


@implementation myScrollView


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

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];

    if (touch.view.tag > 0) {
        touch.view.center = location;
    }

    NSLog(@"tag=%@", [NSString stringWithFormat:@"%i", touch.view.tag]);

}

Answer 1

Make sure you turn on userInteractionEnabled in the UIImageView (it's off by default for those).

Answer 2

Read up on Event Handling and see if you can't figure anything out from that. You also might try canBecomeFirstResponder and becomeFirstResponder.

Answer 3

How do you use these view? Do you create them from IB or from the code? Things to check:

• If you use the IB then make sure that you've set the Class Identity (in View Identity tab in Tools > Inspector) to "myScrollView"
• If you use IB then which parameters have you change from default in both views?
• If you create the views in the code then post your initiation code
• Do you get any method called in "myScrollView" (initializer, for example)?

Answer 4

I'm having the same problem. With the 2.0+ compiler, everything works as expected, but now that I have to use a 3.0+ compiler, my UIScrollView no longer receives the touch events.

Did you ever have any luck resolving this?

UPDATE: I found the answer to the problem here:

http://www.iphonedevsdk.com/forum/iphone-sdk-development/21374-uiscrollview-subclass-not-detecting-touches.html

basically, apple removed this ability in 3.0

"In 2.2.1 and earlier, it was possible to prevent a UIScrollView from scrolling by implementing the UIResponder touch methods in a subclass and not calling the superclass' implementation. This was never supported, and often resulted in inconsistent state on the UIScrollView, but it worked in certain specific situations "