Question

I had a class project consisting in programming a swype-like. I had to do it in java, and you can have a look at it (with the code) here. For this summer, I’d like to port it in ObjC/Cocoa, and then improve it. I intend to use NSButtons for the keyboard keys, like the “Gradient Button” proposed by Interface Builder.

So, I looked about how to handle mouse events (I need mouse pressed, entered, exited, and released). For some objects, it looks like you have to use a delegate, but for NSButton, looks like the methods like -mouseDown and related are in the object itself.

My question is, how do I override the methods in interface builder objects ? I tried creating a subclass of NSButton, and setting my button’s class to this subclass, but without results. Maybe trying to override the methods is not the right way to do it at all, I’m open to every suggestion, even if it is not event-handling related. And if it is relevant, I’m running OS X 10.6, with XCode 4.

Thanks for your time !

Answer 1

A lot will depend on why you need all of the various events. NSButton is a control, and as such works differently than a standard NSView.

If you mostly need to figure out when the button is pressed, you can do this by assigning an action in IB. This is done by creating a void method in your controller class of the form:

- (IBAction) myMouseAction:(id)sender

and then having it do what you need based on receiving the click. Then in IB, you can hook up this action to the button by control-clicking on the button and dragging to your controller class (likely the owner) and selecting your new method when prompted.

If you need fine-grained control, you should consider creating your own NSView subclass and handling the mouse actions yourself, as trying to override controls is a pretty complicated matter. OS X controls were architected for extreme performance, but they’re a bit anachronistic now and generally not worth the work to create your own.

One other thing is that the mouseEntered:, mouseMoved: and mouseExited: events are for handling mouse movement with the mouse button up.

You are going to want to pay attention to: mouseDown:, mouseUp: and mouseDragged: in order to handle events while the mouse button is being held down.