NEW: Nominations are now open for the 2019 Swift Community Awards! >>

How to start an animation immediately after a view appears

Paul Hudson    @twostraws   

Fully updated for Xcode 11.1

If you want a SwiftUI view to start animating as soon as it appears, you should use the onAppear() modifier to attach an animation. I’ll show you the basic code first, then show you two extensions I use to make this process easier.

First, the simple version – this creates a circle that scales up and down forever:

struct ContentView: View {
    @State var scale: CGFloat = 1

    var body: some View {
        Circle()
            .scaleEffect(scale)
            .onAppear {
                let baseAnimation = Animation.easeInOut(duration: 1)
                let repeated = baseAnimation.repeatForever(autoreverses: true)

                return withAnimation(repeated) {
                    self.scale = 0.5
                }
            }
    }
}

If you intend to add initial animations frequently, it’s a smart idea to add some extensions to the View protocol to make it easier. The two extensions below add animate() and animateForever() modifiers that let you customize the animation you want, and wrap up the whole behavior neatly:

extension View {
    func animate(using animation: Animation = Animation.easeInOut(duration: 1), _ action: @escaping () -> Void) -> some View {
        return onAppear {
            withAnimation(animation) {
                action()
            }
        }
    }
}

extension View {
    func animateForever(using animation: Animation = Animation.easeInOut(duration: 1), autoreverses: Bool = false, _ action: @escaping () -> Void) -> some View {
        let repeated = animation.repeatForever(autoreverses: autoreverses)

        return onAppear {
            withAnimation(repeated) {
                action()
            }
        }
    }
}

With that in place, animating our circle is much easier:

Circle()
    .scaleEffect(scale)
    .animateForever(autoreverses: true) { self.scale = 0.5 }

SAVE 20% ON iOS CONF SG The largest iOS conference in Southeast Asia is back in Singapore for the 5th time in January 2020, now with two days of workshops plus two days of talks on SwiftUI, Combine, GraphQL, and more! Save a massive 20% on your tickets by clicking on this link.

Similar solutions…

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let us know!

Average rating: 5.0/5