UIButton inside UIImageView does not respond to ta

问题:

I have a scroll view, which has an image view with an image as a subview, and the image view has a UIButton as one of its subviews. The problem is, I am not able to click on the button. I can SEE the button, but I cannot tap on it.

Can someone tell me what is it that I am messing up? Any help is greatly appreciated! Thanks!

Below is the code:

scrollView = [[UIScrollView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];    
imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"img.jpg"]];
scrollView.delegate = self;
self.view = scrollView;

// add invisible buttons
[self addInvisibleButtons];
[scrollView addSubview:imageView];

addInvisibleButtons has the following code:

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button addTarget:self action:@selector(buttonHandler) forControlEvents:UIControlEventAllEvents];
[button setTitle:@"point" forState:UIControlStateNormal];
button.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
[self.imageView addSubview:button];

回答1:

UIImageView has userInteractionEnabled set to NO/ false by default.

You are adding the button as a subview to the image view. You should set it to YES / true.

回答2:

May I ask why are you adding invisible UIButtons to UIImageView?

Seems like a bad practice, notice Interface Builder doesn't allow you to add UIButton inside them.

If you want an image with touch handling, you can:

UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];
[button addTarget:self action:@selector(buttonHandler) forControlEvents:UIControlEventAllEvents];
[button setTitle:@"point" forState:UIControlStateNormal];
[button setImage:[UIImage imageNamed:@"img.jpg"] forState:UIControlStateNormal];
[button setFrame:CGRectMake(0.0, 0.0, 40.0, 40.0)];

[scrollView addSubview:button];

回答3:

You can have addInvisibleButtons implementation as

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button setBackgroundColor:[UIColor clearColor]];
[button addTarget:self action:@selector(buttonHandler) forControlEvents:UIControlEventAllEvents];
[button setTitle:@"point" forState:UIControlStateNormal];
button.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
self.imageView.userInteractionEnabled = YES;
[self.imageView addSubview:button];

If you want to have UIButton as completely invisible then you need to remove a line [button setTitle:@"point" forState:UIControlStateNormal]; since it use to show text on UIButton which make it visible.

This may resolve your issue.