As of June 22nd this is included in the SwiftUI 2 beta. https://developer.apple.com/documentation/swiftui/scrollviewproxy
The Apple implementation uses just .id(_:)
and I had update issues with that where Views with an id sometimes won't update when their ObservedObject changed. Maybe this has been fixed in the new SwiftUI 2 beta.
Also the Apple implementation only supports iOS 14 so I think this repo is still useful for backwards compatibility.
Adds ScrollViewReader
and ScrollViewProxy
that help you scroll to locations in a ScrollView
To get a ScrollViewProxy you can either use the conveinience init on ScrollView
ScrollView { proxy in
...
}
or add a ScrollViewReader to any View that creates a UIScrollView under the hood
List {
ScrollViewReader { proxy in
...
}
}
The ScrollViewProxy currently has one variable and two functions you can call
/// A publisher that publishes changes to the scroll views offset
public var offset: OffsetPublisher
/// Scrolls to an edge or corner
public func scrollTo(_ alignment: Alignment, animated: Bool = true)
/// Scrolls the view with ID to an edge or corner
public func scrollTo(_ id: ID, alignment: Alignment = .top, animated: Bool = true)
To use the scroll to ID function you have to add an ID to the view you want to scroll to
ScrollView { proxy in
HStack { ... }
.scrollId("someId")
}
This is the only part that is different from the SwiftUI 2.0 implementation because I don't know how to access Views by ID from the .id(_:)
function
Everything put together in an example
struct ScrollViewProxyExample: View {
@State var randomInt = Int.random(in: 0..<200)
@State var proxy: ScrollViewProxy? = nil
@State var offset: CGPoint = .zero
var body: some View {
// GeometryReader for safeAreaInsets on Sticky View
GeometryReader { geometry in
VStack {
ScrollView { proxy in
Text("Sticky View")
.background(Color.white)
.onReceive(proxy.offset) { self.offset = $0 }
.offset(x: offset.x, y: offset.y + geometry.safeAreaInsets.top)
.zIndex(1)
VStack(spacing: 20) {
ForEach(0..<200) { index in
HStack {
Spacer()
Text("Item: \(index)").font(.title)
Spacer()
}.scrollId(index)
}
}
.zIndex(0)
.onAppear {
self.proxy = proxy
}
}
HStack {
Button(action: {
self.proxy?.scrollTo(self.randomInt, alignment: .center)
self.randomInt = Int.random(in: 0..<200)
}, label: {
Text("Go to \(self.randomInt)")
})
Spacer()
Button(action: { self.proxy?.scrollTo(.bottom) }, label: {
Text("Bottom")
})
Spacer()
Button(action: { self.proxy?.scrollTo(.center) }, label: {
Text("Center")
})
}.padding()
}
}
}
}
Want to drop iOS 13 support and move to the SwiftUI 2.0 version?
- Remove the Package
- Add this extension:
extension View {
public func scrollId<ID: Hashable>(_ id: ID) -> some View {
id(id)
}
}
(Or replace all .scrollId with .id)