adjusting label to slider value swift

问题:

I have a slider and label in my swift project. On the storyboard, I control dragged my slider onto my controller class for that page and created an outlet and also an action. I control dragged another label as an outlet. I am trying to update the label based on the slider's value. I don't know where i am going wrong.

Code:

@IBOutlet weak var slider: UISlider!

@IBOutlet weak var sliderVal: UILabel!

@IBAction func sliderValueChanged(sender: UISlider) {
    var currentValue = Int(sender.value)
    println("Slider changing to \(currentValue) ?")
    sliderVal.text = "\(currentValue) Km"
} 

I can see in the log the sliderValueChanged funciton is being called and the log is printing the value but the label's text is not updating. What am I doing wrong?

Update:

I just put a slider object and label on my login screen and used the same methodology and code to change the label text and it worked but it will not work inside my tab bar controller. Does this shed any light on what the issue may be?

回答1:

Update the slider value in Main queue

@IBAction func sliderValueChanged(sender: UISlider) {
    var currentValue = Int(sender.value)
    println("Slider changing to \(currentValue) ?")
    dispatch_async(dispatch_get_main_queue(){
        sliderVal.text = "\(currentValue) Km"
    })
}

I hope this is helpful to you.

回答2:

class ViewController: UIViewController {

@IBOutlet weak var imgView: UIImageView!
@IBOutlet weak var slideroutlet: UISlider!
@IBOutlet weak var lblValue: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

}

@IBAction func slider(_ sender: Any) {

    lblValue.text = String(slideroutlet.value)
    imgView.alpha = CGFloat(slideroutlet.value)
}

回答3:

try this

var currentValue = Int(slider.value)
println("Slider changing to \(currentValue) ?")
startTime.text = "\(currentValue) Km"

回答4:

Swift 3: Select .allEvents for its UIControlEvents.

slider.addTarget(self, action: #selector(ViewController.updateKmsLabel(sender:)), for: .allEvents)
// To use
func updateKmsLabel(sender: UISlider!) {
    let value = Int(sender.value)
    DispatchQueue.main.async {
        self.kmsLabel.text = "\(value)"
        print("Slider value = \(value)")
    }
}

回答5:

If you want to do it programmatically, this is one way.

var slider: UISlider()
var label: UILabel()

func numberValueChanged(sender: UISlider) {
    slider.setValue(Float(Int(slider.value)), animated: true)
    updateLabels(slider.value)
}
fun updateLabels(nV: Float?) {
    if let v = nV {
        self.label.text = "\(v)"
    }
}

slider.addTarget (self,
                 action: #selector(numberValueChanged)
                 forControlEvents: UIControlEvents.ValueChanged
)

Hope this was helpful :)

回答6:

This is what I did and it seemed to have worked:

// For the slider
@IBOutlet weak var slider: UISlider!

// For the label displaying the slider value
@IBOutlet weak var sliderVal: UILabel!

// For the "submit" button action
@IBAction func newSliderValue(_ sender: Any) {
    sliderVal.text = String(slider.value)
}

Note, I used a button to submit my new slider value, not what you did.