检查可动画数据的状态

AnimatableTrigger.swift

//
//  AnimatableTrigger.swift
//  ScrollViewDemo
//
//  Created by Yang Xu on 2022/9/2.
//

import Foundation
import SwiftUI

// 考虑到动画数据插值的不确定性，除了起始点数据外，其他位置数据的判断条件应该设置的宽松些
struct AnimationTrigger<Value: VectorArithmetic>: Animatable, ViewModifier {
    var animatableData: Value {
        get { value }
        set {
            value = newValue
        }
    }

    var value: Value
    let condition: (Value) -> Bool
    var trigger: (Value, Int) -> Void
    let triggerOnce: Bool
    @State var count = 0

    func body(content: Content) -> some View {
        let _ = [condition].forEach {
            if $0(value) {
                DispatchQueue.main.async {
                    if (triggerOnce && count == 0) || !triggerOnce {
                        count += 1
                        trigger(value, count)
                    }
                }
            }
        }

        content
            .background(Color.clear.id(value.magnitudeSquared))
    }
}

extension View {
    func animationTrigger<Value: VectorArithmetic>(
        value: Value,
        condition: @escaping (Value) -> Bool,
        trigger: @escaping (Value, Int) -> Void,
        triggerOnce: Bool = true
    ) -> some View {
        modifier(AnimationTrigger(value: value, condition: condition, trigger: trigger, triggerOnce: triggerOnce))
    }
}

struct TiggerDemo: View {
    @State var degree: CGFloat = 0
    @State var y: CGFloat = 0
    @State var text = ""
    var body: some View {
        VStack {
            Rectangle()
                .fill(.orange)
                .frame(width: 200, height: 200)
                .overlay(Text(text).rotationEffect(.degrees(180)))
                .animationTrigger(value: degree, condition: { $0 == 180 }, trigger: { _, count in
                    text = "旋转结束"
                    withAnimation(.easeOut.delay(0.3)) {
                            y = 200
                        }
                })
                .offset(x: 0, y: y)
                .rotationEffect(Angle.degrees(degree))

            Button("Rotation") {
                withAnimation(.easeInOut(duration: 1)) {
                    degree = 180
                }
            }.buttonStyle(.bordered)
        }
    }
}

struct TiggerPreview:PreviewProvider{
    static var previews: some View{
        TiggerDemo()
    }
}