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July 14, 2024 20:25
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This ScrollView has a modifier called `onScroll`, which is updated when scrolls occur.
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struct ContentView: View { | |
@State var scrollOffset: CGPoint = .zero | |
var body: some View { | |
ObservableScrollView { | |
Text("Hello, world!") | |
.foregroundColor(self.scrollOffset.y == 0 ? .blue : .red) | |
} | |
.onScroll { self.scrollOffset = $0 } | |
} | |
} |
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struct ScrollOffsetPreferenceKey: PreferenceKey { | |
typealias Value = CGPoint | |
static var defaultValue = CGPoint.zero | |
static func reduce(value: inout CGPoint, nextValue: () -> CGPoint) { | |
value = nextValue() | |
} | |
} | |
struct ObservableScrollView<Content> : View where Content : View { | |
var content: Content | |
var axes: Axis.Set | |
var showsIndicators: Bool | |
init(_ axes: Axis.Set = .vertical, showsIndicators: Bool = true, @ViewBuilder content: () -> Content) { | |
self.content = content() | |
self.axes = axes | |
self.showsIndicators = showsIndicators | |
} | |
var body: some View { | |
GeometryReader { outerGeometry in | |
ScrollView(self.axes, showsIndicators: self.showsIndicators) { | |
ZStack(alignment: self.axes == .vertical ? .top : .leading) { | |
GeometryReader { innerGeometry in | |
Color.clear | |
.preference(key: ScrollOffsetPreferenceKey.self, value: CGPoint(x: (outerGeometry.frame(in: .global).minX - innerGeometry.frame(in: .global).minX), y: (outerGeometry.frame(in: .global).minY - innerGeometry.frame(in: .global).minY))) | |
} | |
VStack { | |
self.content | |
} | |
} | |
} | |
} | |
} | |
} | |
extension ObservableScrollView { | |
func onScroll(_ onScroll: @escaping (CGPoint) -> ()) -> some View { | |
self.onPreferenceChange(ScrollOffsetPreferenceKey.self, perform: onScroll) | |
} | |
} |
Wrong implementation of reduce func. Closure will not called.
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If anyone has been looking for a solution I found this really convenient to use
It has all kinds of customisation available, like making the scrollview a grid scrollview , tracking scroll offset putting a header, adjusting padding etc
It is a brilliant solution