How to make a button flash or blink?

Question

I am trying to change a button\'s color (just a flash/blink) to green when a scan is correct and red when there\'s a problem. I am able to do this with a view like so

Answer 1

This will start and stop a flashing button onClick, if you only want to flash the button immediately just use the first statement.

var flashing = false

@IBAction func btnFlash_Clicked(sender: AnyObject) {
        if !flashing{
            self.buttonScan.alpha = 1.0
            UIView.animateWithDuration(0.5, delay: 0.0, options: [.CurveEaseInOut, .Repeat, .Autoreverse, .AllowUserInteraction], animations: {() -> Void in
                self.buttonScan.alpha = 0.0
                }, completion: {(finished: Bool) -> Void in
            })

            flashing = true
        }
    else{
        UIView.animateWithDuration(0.1, delay: 0.0, options: [.CurveEaseInOut, .BeginFromCurrentState], animations: {() -> Void in
            self.buttonScan.alpha = 1.0
            }, completion: {(finished: Bool) -> Void in
        })
    }
}

Swift 5.x version

An updated version with extension.

extension UIView {
    func blink(duration: TimeInterval = 0.5, delay: TimeInterval = 0.0, alpha: CGFloat = 0.0) {
        UIView.animate(withDuration: duration, delay: delay, options: [.curveEaseInOut, .repeat, .autoreverse], animations: {
            self.alpha = alpha
        })
    }
}

To call the function:

button.blink() // without parameters
button.blink(duration: 1, delay: 0.1, alpha: 0.2) // with parameters

Answer 2

with UIViewPropertyAnimator and Swift 5

UIViewPropertyAnimator.runningPropertyAnimator(withDuration: 1, delay: 0, options: [.curveLinear,.repeat], animations: {
       UIView.setAnimationRepeatCount(3000)
       self.buttonScan.alpha = 0.0
 }, completion: {_ in   })

Answer 3

This UIView extension "blinks" a view and changes the background colour:

/**
 Blinks a view with a given duration and optional color.

 - Parameter duration: The duration of the blink.
 - Parameter color: The color of the blink.
 */
public func blink(withDuration duration: Double = 0.25, color: UIColor? = nil) {

    alpha = 0.2
    UIView.animate(withDuration: duration, delay: 0.0, options: [.curveEaseInOut], animations: {
        self.alpha = 1.0
    })

    guard let newBackgroundColor = color else { return }
    let oldBackgroundColor = backgroundColor

    UIView.animate(withDuration: duration, delay: 0.0, options: [.curveEaseInOut], animations: {
        self.backgroundColor = newBackgroundColor
        self.backgroundColor = oldBackgroundColor
    })

}

You would then use as follows:

buttonScan.blink(color: .green)

Answer 4

myButton.alpha = 0.7

UIView.animate(withDuration: 0.3,
                      delay: 1.0,
                    options: [UIView.AnimationOptions.curveLinear, UIView.AnimationOptions.repeat, UIView.AnimationOptions.autoreverse],
                 animations: { myButton.alpha = 1.0 },
                 completion: nil)

Answer 5

Swift 3.0

func animateFlash() {        
    flashView.alpha = 0
    flashView.isHidden = false
    UIView.animate(withDuration: 0.3, animations: { flashView.alpha = 1.0 }) { finished in flashView.isHidden = true }
}

Answer 6

Another smoothly animating version for Swift 5:

 public extension UIView {
  func blink(duration: TimeInterval) {
    let initialAlpha: CGFloat = 1
    let finalAlpha: CGFloat = 0.2
    
    alpha = initialAlpha
    
    UIView.animateKeyframes(withDuration: duration, delay: 0, options: .beginFromCurrentState) {
      UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5) {
        self.alpha = finalAlpha
      }
      
      UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5) {
        self.alpha = initialAlpha
      }
    }
  }
}