NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! >>

How to start an animation immediately after a view appears

Paul Hudson    @twostraws   

Updated for Xcode 12.5

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)

                withAnimation(repeated) {
                    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.

To demonstrate this, the two extensions below add animate() and animateForever() modifiers that let you customize the animation you want and also wrap up the whole behavior neatly:

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

// Create an immediate, looping animation
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()
            }
        }
    }
}

// Try out our extensions with the scaling circle.
struct ContentView: View {
    @State var scale: CGFloat = 1

    var body: some View {
        Circle()
            .scaleEffect(scale)
            .animateForever(autoreverses: true) { scale = 0.5 }
    }
}
Hacking with Swift is sponsored by RevenueCat

SPONSORED Building and maintaining in-app subscription infrastructure is hard. Luckily there's a better way. With RevenueCat, you can implement subscriptions for your app in hours, not months, so you can get back to building your app.

Try it for free

Sponsor Hacking with Swift and reach the world's largest Swift community!

Similar solutions…

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.2/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.