Highlighting a UIControl subclass

Question

basically I need an image button, specifically a custom object that:
1) calls a controller's action when tapped
2) encapsulates custom data
3) is automatically moved by wrapper view (not relevant)

Well, I got all this with a subclass of UIControl (since subclassing UIButton is not recommended and subclassing UIImageView makes difficult to manage the point 1). But now what is the correct way to highlight it? I would like to highlight the control when tapped in any way (even a simple momentary reduction of alpha).

With beginTrackingWithTouch and endTrackingWithTouch I can't recognize the only UIControlEventTouchUpInside event.

A view animation in the controller? It seems to me a rough solution

Is there a simple and immediate solution?

Thanks :(

Answer 1

I think UIControls automatically set their highlighted property correctly, based solely on touch events. What you need is to override -setHighlighted: method to implement a specific algorithm:

- (void) setHighlighted: (BOOL) highlighted {
    [super setHighlighted: highlighted];
    // Only as an example. Caution: looks like a disabled control
    self.alpha = highlighted ? 0.5f : 1.0f;
}

Answer 2

In the interests of keeping this answer up-to-date, here is the Swift version (of Costique's answer).

override var isHighlighted: Bool {
    didSet {
        alpha = self.isHighlighted ? 0.6 : 1.0 // Sets alpha to 0.6 if highlighted, or 1.0 if it's not.
    }
}

You may also like to fade the dimming of the UIControl. To do this, simply place the alpha assignment in an animation block, like this

override var isHighlighted: Bool {
    didSet {
        UIView.animate(withDuration: 0.25) {
            self.alpha = self.isHighlighted ? 0.6 : 1.0
        }
    }
}