Question

I am newbie working on iOS application for iPad. I have successfully implemented a children’s book app using UIImageView. I have also implemented swipe gestures to traverse across the pages. Each page is loaded as single image inside UIImageView and plays an audio narrating the scene.

Now I would like to add some interactivity to my pages. For example, I have a single image loaded in UIImageView which contains few animal characters and some dialect for that particular scene… I want whenever user tap on a particular animal, it should show some movement (may be as if lion is roaring) and my app should play a audio file containing that animal’s sound… how can I achieve this functionality? I need to understand the concept so I can implement it. Should I be having separate images for all animals and load them in their own UIImageView and have all these UIImageViews inside main (or background) UIImageView? I would appreciate if someone can explain me the concept of how such functionality should be implemented.

I think for touches on animals I can define a list of CGRects that will act as hot-spots for each animal on the screen and then play sound files for touched animals but how can I define these hot-spots dynamically? because these would very on each page based on animal’s position on a particular page/image. Also this might not help me with implementing some movement/animation for a particular animal.

Answer 1

An invisible button should work. Use a 1 pixel transparent png, and then size the button dynamically to fit the area you want tapped:

        UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
        btn.frame = CGRectMake(7, 5, 73, 30);
        [btn setImage:[UIImage imageNamed:@"btn_pixel.png"] forState:UIControlStateNormal];
        [btn addTarget:self action:@selector(doSomething) forControlEvents:UIControlEventTouchUpInside];
        [self.view addSubview:btn];

(you don’t need to dealloc the button, because it was not alloc’ed in the first place)

Then, just create a function called “doSomething” that…does what you want. In your example, it would play the animal sound.