Question

I create a UIImageView as below

imageView = [[UIImageView alloc] init];

imageView.image = [UIImage imageNamed:@"military_male_target_001.png"];

imageView.frame = CGRectMake(0, 0, 10, 10);

imageView.alpha = 0.5;

and I have

   - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {...}

in my view controller.

so far so good, the image is displayed on screen and respond to touch down event correctly which means touchesEnded method is invoked when I click inside the image.

but if I add

imageView.userInteractionEnabled = YES

then touchesEnded method won’t be invoked when I click inside the image.
but it is still invoked when I click outside the image.

can anyone tell me how userInteractionEnabled works?
thanks in advance.

Answer 1

The reason why it was not invoked is because you gave imageView permission to capture touches. The imageView will now get the touch event and not forward it on. There is no need to set userInteractionEnabled to YES unless you plan on creating a custom UIImageView that handles the touch event.

Documentation:

New image view objects are configured to disregard user events by
default. If you want to handle events in a custom subclass of
UIImageView, you must explicitly change the value of the
userInteractionEnabled property to YES after initializing the object.