iPhone: Override UIButton buttonWithType to return subclass

Question

I want to be able to create a UIButton with an oversized responsive area. I know that one way to do that is to override the hitTest method in a subclass, but how do I instantiate my custom button object in the first place?

[OversizedButton buttonWithType: UIButtonTypeDetailDisclosure];

doesn't work out of the box because buttonWithType returns a UIButton, not an OversizedButton.

So it seems like I need to override the buttonWithType method as well. Does anyone know how to do this?

@implementation OversizedButton

+ (id)buttonWithType:(UIButtonType)buttonType
{
   // Construct and return an OversizedButton rather than a UIButton
   // Needs to handle special types such as UIButtonTypeDetailDisclosure
   // I NEED TO KNOW HOW TO DO THIS PART
}

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event 
{
   // Return results if touch event was in oversized region
   // I ALREADY KNOW HOW TO DO THIS PART
}

@end

Alternatively, maybe I could create the button using alloc/initWithFrame. But the buttonType property is readonly, so how do you create the custom button types?

Note: I know there are other ways to do this, such as having an invisible button behind the visible one. I don't care for that approach and would prefer to avoid it. Any help on the approach described above would be very helpful. Thanks

Answer 1

The buttonType property is not used anywhere in UIKit, and in your code you could always check -isKindOfClass:, so overwriting +buttonWithType: for this property is rather pointless IMO. Just use

return [[[OversizedButton alloc] initWithFrame:...] autorelease];

(You can override the button type with the undocumented method _setButtonType:.)

Answer 2

UIButton buttonWithType: returns a UIButton or a UIRoundedRectButton, depending on the value of the type parameter.

As UIButton doesn't provide an initWithType: method, I believe it would be dangerous to try and override buttonWithType:.

I suggest you subclass UIControl instead. You can then add a button as a subview to your control, and intercept hitTest:withEvent:.