SwiftUI 在更新 State 时防止 animation

Question

I have a view, that displays an image and when I scroll, this image changes in opacity, scale and offset.

Image(...)
  .resizable()
  .opacity(artworkOpacity)
  .scaleEffect(artworkScale)
  .offset(artworkOffset)

This is defined in struct MyView: View {... } . At the app level I set

MyView()
 .animation(.default)
 .transition(someTransition)

This works well, except for when updating those 3 state variables (opacity, scale and offset), those are animated too! Adding .animation(nil) at the end fixes that, however the transition breaks, the image is the only view that is not transitioning properly.

How can I make the animation only happen during a transition and not while updating state?

I tried with various combinations of enabling and disabling the animation in that view as well as with withAnimation(nil) { // update State }

Thanks!

Answer 1

It's hard to tell exactly what's going on without the full code, but you can add Animation directly to the Transition instead of the whole object.

.transition(AnyTransition.move(edge: .bottom).animation(.easeInOut))

Answer 2

I figured it out!

There is .animation(..., value: ...) , where animation is only added to the view, if the value (which is an equatable), has changed. So the entire view is not affected by the animation, unless the state that defines the current view changes and transition begins.