从View Controller模态切换到另一个控制器后，在View Controller上添加模糊效果

Question

I have a view controller( vc1 ) that contains a button. That button shows another view controller ( vc2 ) modally. presentation style of the segue is set to over current context .

I've also created a UIVisualEffectView on a vc1 programatically (it covers the whole vc1 's view ).

Now, I need to set a visual effect's effect to UIBlurEffect , but after the vc2 is shown modally (which view 's backgroundColour is set to clear , so vc1 is still visible behind vc2 ).

Is it possible to achieve without having to write a custom view controller transition and if so, how this could be done? If you know how to do this, I would appreciate any help or suggestions.

Answer 1

Blur transition does not come by default in iOS. So you need to customise code.
A simple solution would be to add a subview :

Add the following code while transitioning to vc2 :

let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
blurEffectView = UIVisualEffectView(effect: blurEffect)    // Global variable
blurEffectView.frame = view.bounds
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
self.view.addSubview(blurEffectView)

NotificationCenter.default.addObserver(self, selector: #selector(self.removeBlurView), name: NSNotification.Name(rawValue: "removeBlurView"), object: nil)  

Function for removing blur view (in vc1) :

func removeBlurView()
{
    NotificationCenter.default.removeObserver(self)
    blurEffectView.removeFromSuperview()
}  

Add following in vc2 when you dismiss vc2 :

NotificationCenter.default.post(name: NSNotification.Name(rawValue: "removeBlurView"), object: nil)

There are other ways to accomplish this as stated in Ray's tutorial and a closely related tutorial

Answer 2

You can use child ViewController mechanism.

let vc2 = VC2()

vc1.addChildViewController(vc2)
vc2.view.frame = vc1.view.frame

vc1.view.addSubview(vc2.view)
vc2.didMove(toParentViewController: vc1)