SwiftUIアニメーションの詳細

SwiftUIの有能なアニメーション機能がどのように印象的な視覚効果を生み出すかを学びましょう。SwiftUIがどのようにViewを再レンダリングし、何をアニメーションさせるかを決定し、値を補間し、直近のトランザクションのコンテキストを伝達するかを学びましょう。

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関連ビデオ

WWDC23

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2:14 - Pet Avatar - Unanimated

struct Avatar: View {
    var pet: Pet
    @State private var selected: Bool = false

    var body: some View {
        Image(pet.type)
            .scaleEffect(selected ? 1.5 : 1.0)
            .onTapGesture {
                selected.toggle()
            }
    }
}

4:13 - Pet Avatar - Animated

struct Avatar: View {
    var pet: Pet
    @State private var selected: Bool = false

    var body: some View {
        Image(pet.type)
            .scaleEffect(selected ? 1.5 : 1.0)
            .onTapGesture {
                withAnimation {
                    selected.toggle()
                }
            }
    }
}

11:49 - Pet Avatar - Explicit Animation

struct Avatar: View {
    var pet: Pet
    @State private var selected: Bool = false

    var body: some View {
        Image(pet.type)
            .scaleEffect(selected ? 1.5 : 1.0)
            .onTapGesture {
                withAnimation(.bouncy) {
                    selected.toggle()
                }
            }
    }
}

12:48 - UnitCurve Model

let curve = UnitCurve(
    startControlPoint: UnitPoint(x: 0.25, y: 0.1),
    endControlPoint: UnitPoint(x: 0.25, y: 1))
curve.value(at: 0.25)
curve.velocity(at: 0.25)

13:56 - Spring Model

let spring = Spring(duration: 1.0, bounce: 0)
spring.value(target: 1, time: 0.25)
spring.velocity(target: 1, time: 0.25)

17:25 - MyLinearAnimation

struct MyLinearAnimation: CustomAnimation {
    var duration: TimeInterval

    func animate<V: VectorArithmetic>(
        value: V,
        time: TimeInterval,
        context: inout AnimationContext<V>
    ) -> V? {
        if time <= duration {
            value.scaled(by: time / duration)
        } else {
            nil // animation has finished
        }
    }
}

19:50 - MyLinearAnimation with Velocity

struct MyLinearAnimation: CustomAnimation {
    var duration: TimeInterval

    func animate<V: VectorArithmetic>(
        value: V, time: TimeInterval, context: inout AnimationContext<V>
    ) -> V? {
        if time <= duration {
            value.scaled(by: time / duration)
        } else {
            nil // animation has finished
        }
    }

    func velocity<V: VectorArithmetic>(
        value: V, time: TimeInterval, context: AnimationContext<V>
    ) -> V? {
        value.scaled(by: 1.0 / duration)
    }
}

22:44 - Pet Avatar - Animation Modifier

struct Avatar: View {
    var pet: Pet
    @Binding var selected: Bool

    var body: some View {
        Image(pet.type)
            .scaleEffect(selected ? 1.5 : 1.0)
            .animation(.bouncy, value: selected)
            .onTapGesture {
                selected.toggle()
            }
    }
}

23:44 - Pet Avatar - Multiple Animation Modifiers

struct Avatar: View {
    var pet: Pet
    @Binding var selected: Bool

    var body: some View {
        Image(pet.type)
            .shadow(radius: selected ? 12 : 8)
            .animation(.smooth, value: selected)
            .scaleEffect(selected ? 1.5 : 1.0)
            .animation(.bouncy, value: selected)
            .onTapGesture {
                selected.toggle()
            }
    }
}

25:20 - Generic Avatar - Scoped Animation Modifiers

struct Avatar<Content: View>: View {
    var content: Content
    @Binding var selected: Bool

    var body: some View {
        content
            .animation(.smooth) {
                $0.shadow(radius: selected ? 12 : 8)
            }
            .animation(.bouncy) {
                $0.scaleEffect(selected ? 1.5 : 1.0)
            }
            .onTapGesture {
                selected.toggle()
            }
    }
}

28:45 - Pet Avatar - Transaction Modifier

struct Avatar: View {
    var pet: Pet
    @Binding var selected: Bool

    var body: some View {
        Image(pet.type)
            .scaleEffect(selected ? 1.5 : 1.0)
            .transaction(value: selected) {
                $0.animation = $0.avatarTapped
                    ? .bouncy : .smooth
            }
            .onTapGesture {
                withTransaction(\.avatarTapped, true) {
                    selected.toggle()
                }
            }
    }
}

private struct AvatarTappedKey: TransactionKey {
    static let defaultValue = false
}

extension Transaction {
    var avatarTapped: Bool {
        get { self[AvatarTappedKey.self] }
        set { self[AvatarTappedKey.self] = newValue }
    }
}

28:58 - Generic Avatar - Scoped Transaction Modifier

struct Avatar<Content: View>: View {
    var content: Content
    @Binding var selected: Bool

    var body: some View {
        content
            .transaction {
                $0.animation = $0.avatarTapped
                    ? .bouncy : .smooth
            } body: {
                $0.scaleEffect(selected ? 1.5 : 1.0)
            }
            .onTapGesture {
                withTransaction(\.avatarTapped, true) {
                    selected.toggle()
                }
            }
    }
}

private struct AvatarTappedKey: TransactionKey {
    static let defaultValue = false
}

extension Transaction {
    var avatarTapped: Bool {
        get { self[AvatarTappedKey.self] }
        set { self[AvatarTappedKey.self] = newValue }
    }
}

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SwiftUIアニメーションの詳細

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リソース

関連ビデオ

WWDC23