Change existing UIBlurEffect UIBlurEffectStyle programmatically?

Question

I have a Visual Effect View on storyboard connected to my ViewController as an outlet. The effect is burring an ImageView behind it and works great. I'm trying to change the UIBlurEffectStyle from Light to Dark inside a button click IBAction. Any help here would be much appreciated!

@IBOutlet weak var blurView: UIVisualEffectView!

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

@IBAction func changeBlurView() {

    // This is wrong, but is my best attempt so far.
    self.blurView(UIBlurEffectStyle.Dark)   

}

Answer 1

While creating my own app I faced to a similar problem. I do not use IB at all, so everything is done programatically. I looked into the UIVisualEffectView.h and it does not provide any effect change on the fly (hopefully this will change in the future).

So here is my solution (I'm using the latest Swift version, so there is an as! operator):

class CustomVisualEffectView : UIVisualEffectView
{
    deinit
    {
        println("UIVisualEffectView will be destroyed.")
    }
}

class ViewController: UIViewController
{
    var _blurEffect = UIBlurEffect() // global so you can use it for vibrancy effect view as well
    var _blurredEffectView = CustomVisualEffectView()

    let _someSubView = UIView()
    let _someOtherSubView = UIView()

    let _effectChanger = UIButton.buttonWithType(.System) as! UIButton

    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.orangeColor()

        /* create a button to change the effect */
        _effectChanger.setTitle("Change effect!", forState: UIControlState.Normal)
        _effectChanger.frame.size = CGSize(width: 100, height: 20)
        _effectChanger.center = self.view.center
        _effectChanger.addTarget(self, action: Selector("buttonClicked"), forControlEvents: UIControlEvents.TouchUpInside)
        self.view.addSubview(_effectChanger)

        /* here is our effect view */
        _blurEffect = UIBlurEffect(style: self.randomBlurEfffectStyle())
        _blurredEffectView = CustomVisualEffectView(effect: _blurEffect)
        self.layoutEffectView()
        self.view.addSubview(_blurredEffectView)

        /* create two subviews and put them on the effect view */
        _someSubView.frame = CGRectMake(10, 10, 10, 10)
        _someSubView.backgroundColor = UIColor.redColor()
        _blurredEffectView.contentView.addSubview(_someSubView)

        _someOtherSubView.frame = CGRectMake(30, 30, 10, 10)
        _someOtherSubView.backgroundColor = UIColor.greenColor()
        _blurredEffectView.contentView.addSubview(_someOtherSubView)
    }

    func layoutEffectView()
    {
        _blurredEffectView.frame.size = CGSize(width: 100, height: 80)
        _blurredEffectView.center = CGPointMake(_effectChanger.center.x, _effectChanger.center.y - 50)
    }

    func buttonClicked()
    {
        var tempArray = [AnyObject]()

        /* get all subviews from the effect view */
        for view in _blurredEffectView.contentView.subviews
        {
            tempArray.append(view)
            view.removeFromSuperview()
        }
        /* modify your effect view */
        _blurEffect = UIBlurEffect(style: self.randomBlurEfffectStyle())

        /* IMPORTANT: so the old effect view can be destroyed by arc */
        _blurredEffectView.removeFromSuperview()

        _blurredEffectView = CustomVisualEffectView(effect: _blurEffect)
        /* I think this will be really tricky if you will use auto layout */
        self.layoutEffectView()
        self.view.addSubview(_blurredEffectView)

        /* put all subviews back to the effect view*/
        for view in tempArray
        {
            _blurredEffectView.contentView.addSubview(view as! UIView)
        }
    }

    func randomBlurEfffectStyle() -> UIBlurEffectStyle
    {
        let randomBlurEffectStyle : UIBlurEffectStyle

        switch Int(arc4random_uniform(3)) // [0,1,2]
        {
        case 0:
            randomBlurEffectStyle = .ExtraLight
        case 1:
            randomBlurEffectStyle = .Light
        default:
            randomBlurEffectStyle = .Dark
        }

        return randomBlurEffectStyle
    }
}