How to implement range slider in Swift

Question

I'm trying to implement Range Slider and I used custom control called NMRangeSlider.

But when I use it, the slider doesn't appear at all. Could it be also because it's all written in Objective-C?

This is how I've currently implemented it:

var rangeSlider = NMRangeSlider(frame: CGRectMake(16, 6, 275, 34))
rangeSlider.lowerValue = 0.54
rangeSlider.upperValue = 0.94
self.view.addSubview(rangeSlider)

Answer 1

To create a custom Range Slider I found a good solution here: range finder tutorial iOS 8 but I needed this in swift 3 for my project. I updated this for Swift 3 iOS 10 here:

1. in your main view controller add this to viewDidLayOut to show a range slider.

   override func viewDidLayoutSubviews() {
      let margin: CGFloat = 20.0
      let width = view.bounds.width - 2.0 * margin
      rangeSlider.frame = CGRect(x: margin, y: margin + topLayoutGuide.length + 170, width: width, height: 31.0)
   }
   

2. create the helper function to print slider output below viewDidLayoutSubviews()

   func rangeSliderValueChanged() { //rangeSlider: RangeSlider
       print("Range slider value changed: \(rangeSlider.lowerValue) \(rangeSlider.upperValue) ")//(\(rangeSlider.lowerValue) \(rangeSlider.upperValue))
   }
   

3. Create the file RangeSlider.swift and add this to it:

   import UIKit
   
   import QuartzCore
   
   class RangeSlider: UIControl {
   
    var minimumValue = 0.0
    var maximumValue = 1.0
    var lowerValue = 0.2
    var upperValue = 0.8
   
    let trackLayer = RangeSliderTrackLayer()//= CALayer() defined in RangeSliderTrackLayer.swift
    let lowerThumbLayer = RangeSliderThumbLayer()//CALayer()
    let upperThumbLayer = RangeSliderThumbLayer()//CALayer()
    var previousLocation = CGPoint()
   
    var trackTintColor = UIColor(white: 0.9, alpha: 1.0)
    var trackHighlightTintColor = UIColor(red: 0.0, green: 0.45, blue: 0.94, alpha: 1.0)
    var thumbTintColor = UIColor.white
   
    var curvaceousness : CGFloat = 1.0
   
    var thumbWidth: CGFloat {
      return CGFloat(bounds.height)
    }
   
    override init(frame: CGRect) {
      super.init(frame: frame)
   
      trackLayer.rangeSlider = self
      trackLayer.contentsScale = UIScreen.main.scale
      layer.addSublayer(trackLayer)
   
      lowerThumbLayer.rangeSlider = self
      lowerThumbLayer.contentsScale = UIScreen.main.scale
      layer.addSublayer(lowerThumbLayer)
   
      upperThumbLayer.rangeSlider = self
      upperThumbLayer.contentsScale = UIScreen.main.scale
      layer.addSublayer(upperThumbLayer)
   
     }
   
    required init?(coder: NSCoder) {
      super.init(coder: coder)
    }
   
    func updateLayerFrames() {
      trackLayer.frame = bounds.insetBy(dx: 0.0, dy: bounds.height / 3)
      trackLayer.setNeedsDisplay()
   
      let lowerThumbCenter = CGFloat(positionForValue(value: lowerValue))
   
      lowerThumbLayer.frame = CGRect(x: lowerThumbCenter - thumbWidth / 2.0, y: 0.0,
                                  width: thumbWidth, height: thumbWidth)
      lowerThumbLayer.setNeedsDisplay()
   
      let upperThumbCenter = CGFloat(positionForValue(value: upperValue))
      upperThumbLayer.frame = CGRect(x: upperThumbCenter - thumbWidth / 2.0, y: 0.0,
                                  width: thumbWidth, height: thumbWidth)
      upperThumbLayer.setNeedsDisplay()
    }
   
    func positionForValue(value: Double) -> Double {
     return Double(bounds.width - thumbWidth) * (value - minimumValue) /
       (maximumValue - minimumValue) + Double(thumbWidth / 2.0)
    }
   
     override var frame: CGRect {
      didSet {
         updateLayerFrames()
       }
     }
   
      override func beginTracking(_ touch: UITouch, with event: UIEvent?) -> Bool {
         previousLocation = touch.location(in: self)
   
         // Hit test the thumb layers
         if lowerThumbLayer.frame.contains(previousLocation) {
           lowerThumbLayer.highlighted = true
         } else if upperThumbLayer.frame.contains(previousLocation) {
           upperThumbLayer.highlighted = true
         }
   
          return lowerThumbLayer.highlighted || upperThumbLayer.highlighted
      }
   
      func boundValue(value: Double, toLowerValue lowerValue: Double, upperValue: Double) -> Double {
        return min(max(value, lowerValue), upperValue)
      }
   
      override func continueTracking(_ touch: UITouch, with event: UIEvent?) -> Bool {
        let location = touch.location(in: self)
   
        // 1. Determine by how much the user has dragged
        let deltaLocation = Double(location.x - previousLocation.x)
        let deltaValue = (maximumValue - minimumValue) * deltaLocation / Double(bounds.width - thumbWidth)
   
         previousLocation = location
   
         // 2. Update the values
        if lowerThumbLayer.highlighted {
           lowerValue += deltaValue
           lowerValue = boundValue(value: lowerValue, toLowerValue: minimumValue, upperValue: upperValue)
       } else if upperThumbLayer.highlighted {
         upperValue += deltaValue
         upperValue = boundValue(value: upperValue, toLowerValue: lowerValue, upperValue: maximumValue)
       }
   
       // 3. Update the UI
       CATransaction.begin()
       CATransaction.setDisableActions(true)
   
       updateLayerFrames()
   
       CATransaction.commit()
   
        sendActions(for: .valueChanged)
   
         return true
    }
   
     override func endTracking(_ touch: UITouch?, with event: UIEvent?) {
       lowerThumbLayer.highlighted = false
       upperThumbLayer.highlighted = false
     }
   }
   

4. Next add the thumb layer subclass file RangeSliderThumbLayer.swift and add this to it:

     import UIKit
   
     class RangeSliderThumbLayer: CALayer {
        var highlighted = false
        weak var rangeSlider: RangeSlider?
   
     override func draw(in ctx: CGContext) {
       if let slider = rangeSlider {
         let thumbFrame = bounds.insetBy(dx: 2.0, dy: 2.0)
         let cornerRadius = thumbFrame.height * slider.curvaceousness / 2.0
         let thumbPath = UIBezierPath(roundedRect: thumbFrame, cornerRadius: cornerRadius)
   
         // Fill - with a subtle shadow
         let shadowColor = UIColor.gray
         ctx.setShadow(offset: CGSize(width: 0.0, height: 1.0), blur: 1.0, color: shadowColor.cgColor)
         ctx.setFillColor(slider.thumbTintColor.cgColor)
         ctx.addPath(thumbPath.cgPath)
         ctx.fillPath()
   
       // Outline
       ctx.setStrokeColor(shadowColor.cgColor)
       ctx.setLineWidth(0.5)
       ctx.addPath(thumbPath.cgPath)
       ctx.strokePath()
   
       if highlighted {
           ctx.setFillColor(UIColor(white: 0.0, alpha: 0.1).cgColor)
           ctx.addPath(thumbPath.cgPath)
           ctx.fillPath()
       }
     }
    }
   }
   

5. Finally add the track layer subclass file RangeSliderTrackLayer.swift and add the following to it:

    import Foundation
    import UIKit
    import QuartzCore
   
    class RangeSliderTrackLayer: CALayer {
     weak var rangeSlider: RangeSlider?
   
     override func draw(in ctx: CGContext) {
       if let slider = rangeSlider {
         // Clip
         let cornerRadius = bounds.height * slider.curvaceousness / 2.0
         let path = UIBezierPath(roundedRect: bounds, cornerRadius: cornerRadius)
         ctx.addPath(path.cgPath)
   
         // Fill the track
         ctx.setFillColor(slider.trackTintColor.cgColor)
         ctx.addPath(path.cgPath)
         ctx.fillPath()
   
         // Fill the highlighted range
         ctx.setFillColor(slider.trackHighlightTintColor.cgColor)
         let lowerValuePosition =  CGFloat(slider.positionForValue(value: slider.lowerValue))
         let upperValuePosition = CGFloat(slider.positionForValue(value: slider.upperValue))
         let rect = CGRect(x: lowerValuePosition, y: 0.0, width: upperValuePosition - lowerValuePosition, height: bounds.height)
       ctx.fill(rect)
      }
     }
    }
   

Build Run and Get:

Answer 2

UPDATE:

It did not show to me, because it was all white. So the solution, without using any other framework and sticking with this one - you need to set all the views for all the components and then it will display well:

---

I have tried to import it in Swift as I used it before in Objective-C code, but without any luck. If I set everything properly and add it either in viewDidLoad() or viewDidAppear(), nothing gets displayed. One thing is worth mentioning, though - when I enter View Debug Hierarchy, the slider actually is there on the canvas:

But it's simply not rendered with all the colors that I did set before adding in it to the view. For the record - this is the code I used:

override func viewDidAppear(animated: Bool) {
    var rangeSlider = NMRangeSlider(frame: CGRectMake(50, 50, 275, 34))
    rangeSlider.lowerValue = 0.54
    rangeSlider.upperValue = 0.94
    
    let range = 10.0
    let oneStep = 1.0 / range
    let minRange: Float = 0.05
    rangeSlider.minimumRange = minRange
    
    let bgImage = UIView(frame: rangeSlider.frame)
    bgImage.backgroundColor = .greenColor()
    rangeSlider.trackImage = bgImage.pb_takeSnapshot()
    
    let trackView = UIView(frame: CGRectMake(0, 0, rangeSlider.frame.size.width, 29))
    trackView.backgroundColor = .whiteColor()
    trackView.opaque = false
    trackView.alpha = 0.3
    rangeSlider.trackImage = UIImage(named: "")
    
    let lowerThumb = UIView(frame: CGRectMake(0, 0, 8, 29))
    lowerThumb.backgroundColor = .whiteColor()
    let lowerThumbHigh = UIView(frame: CGRectMake(0, 0, 8, 29))
    lowerThumbHigh.backgroundColor = UIColor.blueColor()
    
    rangeSlider.lowerHandleImageNormal = lowerThumb.pb_takeSnapshot()
    rangeSlider.lowerHandleImageHighlighted = lowerThumbHigh.pb_takeSnapshot()
    rangeSlider.upperHandleImageNormal = lowerThumb.pb_takeSnapshot()
    rangeSlider.upperHandleImageHighlighted = lowerThumbHigh.pb_takeSnapshot()
    
    self.view.addSubview(rangeSlider)

    self.view.backgroundColor = .lightGrayColor()
}

Using the method for capturing the UIView as UIImage mentioned in this question:

extension UIView {
    func pb_takeSnapshot() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.mainScreen().scale)
        drawViewHierarchyInRect(self.bounds, afterScreenUpdates: true)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

---

Other solution:

You can also try sgwilly/RangeSlider instead, it's written in Swift and therefore you won't even need a Bridging Header.