# onScrollPhaseChange(_:) Adds an action to perform when the scroll phase of the first scroll view in the hierarchy changes. ``` nonisolated func onScrollPhaseChange(_ action: @escaping (ScrollPhase, ScrollPhase) -> Void) -> some View ``` ## Parameters `action` A closure to run when the scroll phase changes. - oldPhase: The old scroll phase. - newPhase: The new scroll phase. ## Discussion Use this modifier to be informed of changes to a scroll view’s phase. A scroll view may be in a variety of different phases like panning or decelerating. See [`ScrollPhase`](/documentation/SwiftUI/ScrollPhase) for more information on the phases of a scroll view. When the phase of a scroll view changes, the system invokes the action you provide. In the following example, a selection binding is updated when the scroll view transitions to the [`ScrollPhase.decelerating`](/documentation/SwiftUI/ScrollPhase/decelerating) or [`ScrollPhase.idle`](/documentation/SwiftUI/ScrollPhase/idle) phase. ``` @Binding var selection: SelectionValue? ScrollView { // ... } .onScrollPhaseChange { _, newPhase in if newPhase == .decelerating || newPhase == .idle { selection = updateSelection() } } ``` The system can also provide you with the geometry of the scroll view at the time of the phase change. You can use the geometry to understand where the scroll view has come or gone between the phase changes and update dependent state on that information. In the following example, whether toolbar content is hidden is determined based on the direction of the last user initiated scroll. ``` @Binding var hidesToolbarContent: Bool @State private var lastOffset: CGFloat = 0.0 ScrollView { // ... } .onScrollPhaseChange { oldPhase, newPhase, context in if newPhase == .interacting { lastOffset = context.geometry.contentOffset.y } if oldPhase == .interacting, newPhase != .animating, context.geometry.contentOffset.y - lastOffset < 0.0 { hidesToolbarContent = true } else { hidesToolbarContent = false } } ``` If multiple scroll views are found within the view hierarchy, only the first one will invoke the closure you provide and a runtime issue will be logged. For example, in the following view, only the vertical scroll view will have its phase changes invoke the provided closure. ``` VStack { ScrollView(.vertical) { ... } ScrollView(.horizontal) { ... } } .onScrollPhaseChange { ... } ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)