iOS fetch UIButton current UIControlEventType at @selector

Question

let aButton = UIButton()
a.addTarget(self, action: "handler:", forControlEvents: .TouchUpInside)

func handler(btn: UIButton) {
    //Is there anyway can I know the controlEvent is "TouchUpInside" in this method?
}

as the example above, I wanna know the ControlEventType at @selector, could not found the correct API or it's impossible?

method is called if and only if control event is touchUpInside. look at this http://stackoverflow.com/questions/19076741/how-to-distinguish-between-fired-events-for-a-uibutton-callback-action — Saurabh Prajapati, Jul 14 '15 at 11:55

score 2 · Accepted Answer · edited May 23 '17 at 10:26

You can either provide different methods for the different control events:

a.addTarget(self, action: "touchDownHandler:", forControlEvents: .TouchDown)
a.addTarget(self, action: "touchUpHandler:", forControlEvents: .TouchUpInside)

func touchDownHandler(btn: UIButton) {
}

func touchUpHandler(btn: UIButton) {
}

As noted in another answer you can also get the event in your handler and inspect that for the type of touch, here it is in Swift:

a.addTarget(self, action: "handleTouch:event:", forControlEvents: .AllTouchEvents)

// ...

func handleTouch(button: UIButton, event: UIEvent) {
    if let touch = event.touchesForView(button)?.first as? UITouch {
        switch touch.phase {
        case .Began:
            println("touch began")

        case .Ended:
            println("touch ended")

        case .Moved:
            println("touch moved")

        case .Cancelled:
            println("touch cancelled")

        case .Stationary:
            println("touch stationary")

        }
    }
}

score 2 · Answer 2 · edited May 23 '17 at 11:44

You can change your action to take the event parameter, like this:

[button addTarget:self action:@selector(callback:event:) forControlEvents:UIControlEventTouchDown | UIControlEventTouchCancel];

-(void)callback:(UIButton *)button (UIEvent*)event {
    ...
}

Adding a second parameter to your callback will make Cocoa pass the event to you, so that you could check what has triggered the callback.

thanks to dasblinkenlight

score 0 · Answer 3 · answered Jul 14 '15 at 11:58

I'm afraid you have to create multiple functions (which could then call a common handler function, of course):

a.addTarget(self, action: "handleTouchUpInside:", forControlEvents: .TouchUpInside)
a.addTarget(self, action: "handleTouchUpOutside:", forControlEvents: .TouchUpOutside)

You are allowed to add an action which accepts an extra UIEvent parameter, but unfortunately it won't contain any information about the control event type.

iOS fetch UIButton current UIControlEventType at @selector

3 Answers3

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