iPhone “slide to unlock” animation

Question

Any ideas as to how Apple implemented the \"slide to unlock\" (also, \"slide to power off\" is another identical example) animation?

I thought about some sort of ani

Answer 1

Here's a SwiftUI version:

struct Shimmer: AnimatableModifier {

    private let gradient: Gradient

    init(sideColor: Color = Color(white: 0.25), middleColor: Color = .white) {
        gradient = Gradient(colors: [sideColor, middleColor, sideColor])
    }

    @State private var position: CGFloat = 0
    var animatableData: CGFloat {
        get { position }
        set { position = newValue }
    }

    func body(content: Content) -> some View {
        content
            .overlay(LinearGradient(
                        gradient: gradient,
                        startPoint: .init(x: position - 0.2 * (1 - position), y: 0.5),
                        endPoint: .init(x: position + 0.2 * position, y: 0.5)))
            .mask(content)
            .onAppear {
                withAnimation(Animation
                                .linear(duration: 2)
                                .delay(1)
                                .repeatForever(autoreverses: false)) {
                    position = 1
                }
            }
    }
}

Use it like this:

Text("slide to unlock")
    .modifier(Shimmer())