为什么 SwiftUI 不透明度动画在 Gesture 的 onEnded 方法中失败？

Question

如下图所示，第二次点击紫色矩形不会触发蓝色矩形淡入的动画。这是 Bug 还是模糊功能？

感谢您的热心回复！

trying to toggle the opacity of the big blue rectangle with animation (sorry, not enough reputation to post images)

struct FadeTestView: View {
  @State var fade: Bool = false
  var body: some View {
    VStack{
      Rectangle().fill(.blue).frame(width: 100, height: 100, alignment: .center)
        .opacity(fade ? 0 : 1)
      
      Button(action: {
        withAnimation(.easeInOut(duration: 2)){ fade.toggle() }
      }){
        Circle().fill(.yellow).frame(width: 50, height: 50, alignment: .center)
      }
      
      Rectangle().fill(.purple).frame(width: 50, height: 50, alignment: .center)
        .gesture(TapGesture().onEnded{
          withAnimation(.easeInOut(duration: 2)){ fade.toggle() }
        })
    }
  }
}

Answer 1

我认为这是 .opacity 的错误。变通办法似乎根本就没有一直更改为 0。

        Rectangle()
            .fill(.blue)
            .frame(width: 100, height: 100, alignment: .center)
            .opacity(fade ? 0.01 : 1)

任何低于 .opacity 的值都被视为 0，但 .01 实际上是透明的。

Answer 2

如果只是为了改变不透明度，请使用线性

struct FadeTestView: View {
@State var fade: Bool = false
var body: some View {
VStack{
  Rectangle().fill(.blue).frame(width: 100, height: 100, alignment:       .center)
    
    .opacity(fade ? 0 : 1)
  
  Button(action: {
      withAnimation(.linear(duration: 2)){ fade.toggle() }
  }){
    Circle().fill(.yellow).frame(width: 50, height: 50, alignment: .center)
  }
  
  Rectangle().fill(.purple).frame(width: 50, height: 50, alignment: .center)
        .onTapGesture() {
            withAnimation(.linear(duration: 2)){
                fade.toggle()
            }
        }
       
}
}

}

为什么 SwiftUI 不透明度动画在 Gesture 的 onEnded 方法中失败？

Why does SwiftUI opacity animation fail in Gesture's onEnded method?

animation

opacity

ios

swiftui