Tap on UISliders created programmatically

Question

Am trying solution in Swift 4 as suggested by Diogo in Tap on UISlider to Set the Value - on a set of UISliders defined programmatically, but I can't reference the UISlider insider the Selector.

In viewDidLoad() with 'slider' defined as any UISlider in a collection of UISliders running inside a For... statement:

let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(sliderTapped(_: slider:)))
slider.addGestureRecognizer(tapGestureRecognizer)

Selector:

@objc func sliderTapped(_ gestureRecognizer:UIGestureRecognizer, slider:UISlider) {

    let pointTapped: CGPoint = gestureRecognizer.location(in: assessView)        
    let positionOfSlider: CGPoint = slider.convert(slider.bounds.origin, to: assessView)
    let widthOfSlider: CGFloat = slider.bounds.size.width

    let moveDistance = sqrt(Double(pow(Double(pointTapped.x - positionOfSlider.x),2) + pow(Double(pointTapped.y - positionOfSlider.y),2)))

    var newValue: CGFloat
    if pointTapped.x < 10 {
        newValue = 0
    } else {
        newValue = (CGFloat(moveDistance) * CGFloat(slider.maximumValue) / widthOfSlider)
    }

    slider.setValue(Float(newValue), animated: true)
}

Also, 'slider' is added to a subview under 'assessView' - should this be the target of the taprecogniser?

When printing out the 'slider' in the console it states that 'slider' is uninitialized. Any reflections on how to deal with this?

score 1 · Accepted Answer · answered May 14 '18 at 22:03

You can't create your own arbitrary signature for the selector used in a target/selector pair.

Update your selector to only take the gesture. You can get the slider from the gesture.

You also need to check the state of the gesture.

Update your setup:

let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(sliderTapped))
slider.addGestureRecognizer(tapGestureRecognizer)

Then update your method:

@objc func sliderTapped(_ gesture: UITapGestureRecognizer) {
    guard gesture.state == .ended else { return }
    guard let slider = gesture.view as? UISlider else { return }

    let pointTapped: CGPoint = gesture.location(in: assessView)        
    let positionOfSlider: CGPoint = slider.convert(slider.bounds.origin, to: assessView)
    let widthOfSlider: CGFloat = slider.bounds.size.width

    let moveDistance = sqrt(Double(pow(Double(pointTapped.x - positionOfSlider.x),2) + pow(Double(pointTapped.y - positionOfSlider.y),2)))

    var newValue: CGFloat
    if pointTapped.x < 10 {
        newValue = 0
    } else {
        newValue = (CGFloat(moveDistance) * CGFloat(slider.maximumValue) / widthOfSlider)
    }

    slider.setValue(Float(newValue), animated: true)
}

This works! there is simpler code here: ```guard gesture.state == .ended else { return } guard let slider = gesture.view as? UISlider else { return } let pointTapped = gesture.location(in: slider) let value = Float(pointTapped.x / slider.bounds.size.width) slider.setValue(Float(value), animated: true)``` — mylittleswift, Nov 25 '19 at 22:21

score 0 · Answer 2 · answered May 14 '18 at 21:54

0

According to the UIGestureRecognizer documentation (here):

The action methods invoked must conform to one of the following signatures:
@IBAction func myActionMethod()
@IBAction func myActionMethod(_ sender: UIGestureRecognizer)

If you are not adding the same instance of the recognizer to other views, you can get the slider by accessing the view property of the recognizer.

answered May 14 '18 at 21:54

Adri

530
2
8

Thanks Adri - will try out the concrete solution proposed by rmaddy a over and come back. – Kasper Olsen May 14 '18 at 22:24

Tap on UISliders created programmatically

2 Answers2