TouchUpInside boundaries outside of UIButton

ios, swift, uibutton

Solution

Okay it's taken a fair bit of digging to get to the bottom of this but a couple of helpful Obj-C links...

UIControlEventTouchDragExit triggers when 100 pixels away from UIButton

How to correctly subclass UIControl?

http://www.bytearray.org/?p=5336 (particularly line 89)

...and it seems that the behaviour is standard due to the touch interface (personally I instinctively find the default zone excessive but I'm sure Apple did its homework) and can be overridden by either sub-classing UIControl or interrogating the position of the control event.

I've opted for the latter and here's an implementation specifically in Swift:

// ViewController.swift

import UIKit

class ViewController: UIViewController {
    let buttonCount = 3

    override func viewDidLoad() {
        super.viewDidLoad()

        for currentTag:Int in 1...buttonCount{
            var currentButton = UIButton.buttonWithType(UIButtonType.System) as UIButton
            currentButton.frame = CGRectMake(50, Float(currentTag*50), 120, 50)
            currentButton.backgroundColor = UIColor.greenColor()
            currentButton.setTitle("Test Button \(currentTag)", forState: UIControlState.Normal)
            currentButton.contentEdgeInsets = UIEdgeInsets(top:3,left:6,bottom:3,right:6)
            currentButton.tag = currentTag
            currentButton.addTarget(self,
                action: "btn_TouchDown:",
                forControlEvents: UIControlEvents.TouchDown)
            currentButton.addTarget(self,
                action: "btn_TouchDragExit:",
                forControlEvents: UIControlEvents.TouchDragExit)
            currentButton.addTarget(self,
                action: "btn_TouchUpInside:event:",
                forControlEvents: UIControlEvents.TouchUpInside)
            currentButton.sizeToFit()

            self.view.addSubview(currentButton)
        }//next
    }// end viewDidLoad()


    func btn_TouchDown(sender:UIButton!){
        println("TouchDown event: \(sender.tag)\n")
    }

    func btn_TouchDragExit(sender:UIButton!){
        println("TouchDragExit event: \(sender.tag)\n")
    }

    func btn_TouchUpInside(sender:UIButton!,event:UIEvent!){
        println("TouchUpInside event: \(sender.tag)")

        var currentTouch:CGPoint = event.allTouches().anyObject().locationInView(sender)
        println( "Point: \(currentTouch.x), \(currentTouch.y)\n" )
        if currentTouch.x > sender.frame.width{return}
        if currentTouch.x < 0 {return}
        if currentTouch.y > sender.frame.height{return}
        if currentTouch.y < 0 {return}

        println("Event ended within frame!")
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


    override func prefersStatusBarHidden() -> Bool {
        return true
    }
}

Problem

I'm currently tying to familiarise myself with UIKit under Swift and work out the best way of adding UI elements programmatically. However I'm finding that a touch can end way outside the button in which it began yet still register as a TouchUpInside event. The ViewController below is from a single view application and it is straightforward to start a touch on, say, button 17, end it on button 18 and still have buttonAction() declare "Button tapped: 17". Any idea what I'm missing here? (Edit: This is under Xcode 6 beta 3 BTW.) ``` // ViewController.swift import UIKit class ViewController: UIViewController { let scrollView:UIScrollView = UIScrollView() var GWIDTH:Float = 0.0 var GHEIGHT:Float = 0.0 override func viewDidLoad() { super.viewDidLoad() GWIDTH = self.view.bounds.size.width GHEIGHT = self.view.bounds.size.height scrollView.frame = CGRectMake(10, 10, GWIDTH-10, GHEIGHT-20) scrollView.contentSize = CGSize(width:GWIDTH-20, height: 0) self.view.addSubview(scrollView) for currentTag in 1...30{ var currentButton = UIButton.buttonWithType(UIButtonType.System) as UIButton currentButton.frame = CGRectMake(100, scrollView.contentSize.height, 100, 50) currentButton.backgroundColor = UIColor.greenColor() currentButton.setTitle("Test Button \(currentTag)", forState: UIControlState.Normal) currentButton.tag = currentTag currentButton.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside) scrollView.addSubview(currentButton) scrollView.contentSize = CGSize(width:GWIDTH-20,height:2.0+currentButton.frame.size.height+currentButton.frame.origin.y) }//next }// end viewDidLoad() func buttonAction(sender:UIButton!){ println("Button tapped: \(sender.tag)") } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() } override func prefersStatusBarHidden() -> Bool { return true } } ```

Original source

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