Is there a method to blur a background in SwiftUI?

问题:

I'm looking to blur a view's background but don't want to have to break out into UIKit to accomplish it (eg. a UIVisualEffectView) I'm digging through docs and got nowhere, seemingly there is no way to live-clip a background and apply effects to it. Am I wrong or looking into it the wrong way?

回答1:

I haven't found a way to achieve that in SwiftUI yet, but you can use UIKit stuff via UIViewRepresentable protocol.

struct BlurView: UIViewRepresentable {

    let style: UIBlurEffect.Style

    func makeUIView(context: UIViewRepresentableContext<BlurView>) -> UIView {
        let view = UIView(frame: .zero)
        view.backgroundColor = .clear
        let blurEffect = UIBlurEffect(style: style)
        let blurView = UIVisualEffectView(effect: blurEffect)
        blurView.translatesAutoresizingMaskIntoConstraints = false
        view.insertSubview(blurView, at: 0)
        NSLayoutConstraint.activate([
            blurView.heightAnchor.constraint(equalTo: view.heightAnchor),
            blurView.widthAnchor.constraint(equalTo: view.widthAnchor),
        ])
        return view
    }

    func updateUIView(_ uiView: UIView,
                      context: UIViewRepresentableContext<BlurView>) {

    }

}

Demo:

struct ContentView: View {

    var body: some View {
        NavigationView {
            ZStack {
                List(1...100) { item in
                    Rectangle().foregroundColor(Color.pink)
                }
                .navigationBarTitle(Text("A List"))
                ZStack {
                    BlurView(style: .light)
                        .frame(width: 300, height: 300)
                    Text("Hey there, I'm on top of the blur")

                }
            }
        }
    }

}

I used ZStack to put views on top of it.

ZStack {
 // List
 ZStack {
    // Blurred View
    // Text
 }
}

And ends up looking like this:

回答2:

The Native SwiftUI way:

You can add .blur() modifier on anything you need to be blurry like:

struct ContentView: View {

    var body: some View {
        ZStack {
            Image("BG")
                .resizable()
                .scaledToFill()
                .edgesIgnoringSafeArea(.all)
                .blur(radius: 20) // <- this is the important modifier. The rest is just for demo

            Text("Hello \nSwiftUI Blur Effect")
                .font(.largeTitle)
                .fontWeight(.black)
                .foregroundColor(.white)
        }
    }
}

_{Note the top and bottom of the view}

Note that you can Group multiple views and blur them together.

---

The Visual Effect View:

You can define a VisualEffectView with just 5 lines of code:

struct VisualEffectView: UIViewRepresentable {
    var effect: UIVisualEffect?
    func makeUIView(context: UIViewRepresentableContext<Self>) -> UIVisualEffectView { UIVisualEffectView() }
    func updateUIView(_ uiView: UIVisualEffectView, context: UIViewRepresentableContext<Self>) { uiView.effect = effect }
}

Usage Example:

struct ContentView: View {

    var body: some View {
        ZStack {
            Image("BG")
                .resizable()
                .scaledToFill()
                .edgesIgnoringSafeArea(.all)

            VisualEffectView(effect: UIBlurEffect(style: .dark))
                .edgesIgnoringSafeArea(.all)

            Text("Hello \nVisual Effect View")
                .font(.largeTitle)
                .fontWeight(.black)
                .foregroundColor(.white)
        }
    }
}

回答3:

The simplest way is here by Richard Mullinix:

struct Blur: UIViewRepresentable {
    let style: UIBlurEffect.Style = .systemMaterial

    func makeUIView(context: Context) -> UIVisualEffectView {
        return UIVisualEffectView(effect: UIBlurEffect(style: style))
    }

    func updateUIView(_ uiView: UIVisualEffectView, context: Context) {
        uiView.effect = UIBlurEffect(style: style)
    }
}

Then just use it somewhere in your code like background:

    //...
    MyView()
        .background(Blur(style: .systemUltraThinMaterial))