Images and buttons

Question

I want to load an image onto the screen and allow the user to touch parts of the image to trigger an event.
I can get an UIImageView with an image to load onto the screen, but it seems to hide the button I put in place with IB. How can I "hide" the image behind the button so the button will work?
Is this easier working out of the viewcontroller object or creating a uiview object? Right now, I can only get the image to load if I use a uiview object.
Should I define the IBAction method for the button in the uiviewcontroller or uiview?

Answer 1

If you need to know where the touch occurred on the image, take darkpegusus' advice and subclass UIImageView so you can override the touch methods.
However if you only need to know if the image was touched and don't need the location, a button would work fine and is much easier to program than a subclass.
You asked how to hide the image. For that all you'd need to do is put a button on top of the image. You'd do that in IB by dragging a button onto the image, then going to the xib window (the window with icons such as File's Owner; if you don't see it select Window->Document). At the left end of the toolbar select ViewMode->center (the switch with 4 horizontal lines). Now expand the content view (probably the bottom icon; it won't be called content view, but it's the view that contains your image view). You should now see your UIImageView and your UIButton as children of the content view. The button will be on top of the image view when it's lower in the list. If the button isn't at the bottom of the list, drag it lower. The button may try to leave the list of children, but make sure it goes into the list (indented) at the bottom. You should now see the button on top of the image view.
Note that the above procedure makes the button hide the part of the view under it. But I suspect you may have meant "Put the button over the image so it will respond to a touch, but hide the button". If that's what you want, you need an invisible button. You can't do this by setting the button's alpha to zero, because it will no longer respond (alpha needs to be above 0.2 before a view will respond to touch). You also can't change the background of a rounded rect button to clear. It will always be drawn white.
For an invisible button, what you want is a "custom" type UIButton. Select the button, bring up the Attributes Inspector and at the top of the panel, change the Type to Custom. Next select the image view and bring up the Size Inspector. Write down the x, y, width, height for the image view, then select the button again and set it's dimensions to those numbers in the Size Inspector. You should now have an Invisible button which exactly covers the image view.
Re your last questions, your UIImageView and UIButton must be added to a view (the IB editor window might be named View Controller, but when you add something to that editor window, it will be added to the controller's view, not the controller itself. I.e. whether or not you use a view controller, controls and other subview are always added to a view object as shown in the xib window.
If you have a controller, you should "control" the button and image from the controller object. In other words, you'll have your own subclass of UIViewController with instance variables for all the controls on the content view (the view controller's view). You can specify IBOutlet for those instance vars and connect them to the correct controls in IB. Similarly, your view controller subclass should define IBAction methods for each button (or other control), and you make the connection from the buttons to the methold in IB.