Ios 如何让替换视图淡入旧视图而不是交叉淡入淡出

一种方法可能是将自定义过渡应用于背景视图.我只是简单地测试了一下，但是添加了这个之后，俯视图和俯视图在转换过程中看起来是匹配的.

import SwiftUI
import PlaygroundSupport

struct AllOrNothingTransition: Animatable, ViewModifier {
    
    var animatableData: CGFloat = 0
    
    func body(content: Content) -> some View {
        // The goal is for `content` to remain in place, unchanged,
        // until the transition completes and it is removed, so we
        // simply pass it back unchanged regardless of the value
        // of `animatableData`.
        content
    }
}

extension AnyTransition {
    static var allOrNothing: AnyTransition {
        // For this use case, the specific values passed in as `animatableData`
        // are not important, as long as they differ from each other.
        // SwiftUI needs to have differing values to interpolate between,
        // otherwise it will assume there is nothing to animate and
        // remove the transitioning view immediately at the start of
        // of the transition (this is based on observation, not a knowledge
        // of the inner workings of SwiftUI).
        AnyTransition.modifier(
            active: AllOrNothingTransition(animatableData: 0),
            identity: AllOrNothingTransition(animatableData: 1)
        )
    }
}

struct ContentView: View {
    let transaction = Transaction(animation: .linear(duration: 10))
    let imageURL = URL(string: "https://www.nasa.gov/sites/default/files/thumbnails/image/main_image_star-forming_region_carina_nircam_final-5mb.jpg")!
    
    var body: some View {
        VStack(spacing: 10) {
            AsyncImage(url: imageURL, transaction: transaction) { phase in
                
                if let img = phase.image {
                    img.resizable()
                } else {
                    Color.red
                        .transition(.allOrNothing)
                }
            }
            .aspectRatio(CGSize(width: 3600, height: 2085), contentMode: .fit)

            AsyncImage(url: imageURL, transaction: transaction) { phase in
                ZStack {
                    Color.red
                    
                    if let img = phase.image {
                        img.resizable()
                    }
                }
            }
            .aspectRatio(CGSize(width: 3600, height: 2085), contentMode: .fit)
        }
        .frame(width: 500)
        .padding(10)
        .background(Color.yellow)
    }
}

PlaygroundPage.current.setLiveView(ContentView())