SwiftUI - 脉动动画和更改颜色

Question

我正在尝试根据某物的状态更改动画的颜色。颜色更改有效，但它会使用它为之前的（橙色）颜色设置动画。我不太明白为什么两种颜色都显示出来。有任何想法吗？

struct PulsatingView: View {

    var state = 1

    func colourToShow() -> Color {
        switch state {
        case 0:
            return Color.red
        case 1:
            return Color.orange
        case 2:
            return Color.green
        default:
            return Color.orange
        }
    }

    @State var animate = false
    var body: some View {
        VStack {
            ZStack {
                Circle().fill(colourToShow().opacity(0.25)).frame(width: 40, height: 40).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow().opacity(0.35)).frame(width: 30, height: 30).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow().opacity(0.45)).frame(width: 15, height: 15).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow()).frame(width: 6.25, height: 6.25)
            }
            .onAppear { self.animate.toggle() }
            .animation(Animation.easeInOut(duration: 1.5).repeatForever(autoreverses: true))
        }
    }
}

Answer 1

您更改了颜色，但永久设置的动画视图不会更改 - 它保持设置并按指定继续 - 永远。所以需要重新设置动画。

请在下面找到一个完整的模块演示代码（使用 Xcode 11.2 / iOS 13.2 测试）。这个想法是使用ObservableObject视图模型，因为它允许刷新视图并在接收时执行一些操作。因此，接收颜色变化可以重置和查看颜色和动画。

import SwiftUI
import Combine

class PulsatingViewModel: ObservableObject {
    @Published var colorIndex = 1
}

struct PulsatingView: View {

    @ObservedObject var viewModel: PulsatingViewModel

    func colourToShow() -> Color {
        switch viewModel.colorIndex {
        case 0:
            return Color.red
        case 1:
            return Color.orange
        case 2:
            return Color.green
        default:
            return Color.orange
        }
    }

    @State var animate = false
    var body: some View {
        VStack {
            ZStack {
                Circle().fill(colourToShow().opacity(0.25)).frame(width: 40, height: 40).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow().opacity(0.35)).frame(width: 30, height: 30).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow().opacity(0.45)).frame(width: 15, height: 15).scaleEffect(self.animate ? 1 : 0)
                Circle().fill(colourToShow()).frame(width: 6.25, height: 6.25)
            }
            .onAppear { self.animate = true }
            .animation(animate ? Animation.easeInOut(duration: 1.5).repeatForever(autoreverses: true) : .default)
            .onReceive(viewModel.$colorIndex) { _ in
                self.animate = false
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
                    self.animate = true
                }
            }
        }
    }
}

struct TestPulseColorView: View {
    private var model = PulsatingViewModel()
    var body: some View {
        VStack {
            Spacer()
            PulsatingView(viewModel: model)
            Spacer()
            Button("Toggle") { self.model.colorIndex = Int.random(in: 0...2) }
        }
    }
}

struct TestPulseColorView_Previews: PreviewProvider {
    static var previews: some View {
        TestPulseColorView()
    }
}