Is there a way to change the default scrolling animation of the ScrollView
by using ScrollViewReader
?
I have tried different things but the animation remained as the default one.
withAnimation(.easeInOut(duration: 60)) { // <-- Not working (changes nothing)
proxy.scrollTo(50, anchor: .center)
}
As you can see here: (Obviously this is faster than a 1 minute animation)
struct ContentView: View {
var body: some View {
ScrollView {
ScrollViewReader { proxy in
Button("Scroll to") {
withAnimation(.easeInOut(duration: 60)) {
proxy.scrollTo(50, anchor: .center)
}
}
ForEach(0..<100) { i in
Rectangle()
.frame(width: 200, height: 100)
.foregroundColor(.green)
.overlay(Text("\(i)").foregroundColor(.white).id(i))
}
.frame(maxWidth: .infinity)
}
}
}
}
Maybe that's just not possible yet?
Thanks!
SwiftUI has built-in support for animations with its animation() modifier. To use this modifier, place it after any other modifiers for your views, tell it what kind of animation you want, and also make sure you attach it to a particular value so the animation triggers only when that specific value changes.
New in iOS 14 If you want to programmatically make SwiftUI's ScrollView move to a specific location, you should embed a ScrollViewReader inside it. This provides a scrollTo() method that can move to any view inside the parent scrollview, just by providing its anchor.
A view that provides programmatic scrolling, by working with a proxy to scroll to known child views.
withAnimation() takes a parameter specifying the kind of animation you want, so you could create a three-second linear animation like this: withAnimation(.linear(duration: 3)) Explicit animations are often helpful because they cause every affected view to animate, not just those that have implicit animations attached.
I had the same problem sometime ago, and I found this code in GitHub:
Scrollable SwuifUI Wrapper
Create a custom UIScrollView in a Swift file with this code:
import SwiftUI
struct ScrollableView<Content: View>: UIViewControllerRepresentable, Equatable {
// MARK: - Coordinator
final class Coordinator: NSObject, UIScrollViewDelegate {
// MARK: - Properties
private let scrollView: UIScrollView
var offset: Binding<CGPoint>
// MARK: - Init
init(_ scrollView: UIScrollView, offset: Binding<CGPoint>) {
self.scrollView = scrollView
self.offset = offset
super.init()
self.scrollView.delegate = self
}
// MARK: - UIScrollViewDelegate
func scrollViewDidScroll(_ scrollView: UIScrollView) {
DispatchQueue.main.async {
self.offset.wrappedValue = scrollView.contentOffset
}
}
}
// MARK: - Type
typealias UIViewControllerType = UIScrollViewController<Content>
// MARK: - Properties
var offset: Binding<CGPoint>
var animationDuration: TimeInterval
var showsScrollIndicator: Bool
var axis: Axis
var content: () -> Content
var onScale: ((CGFloat)->Void)?
var disableScroll: Bool
var forceRefresh: Bool
var stopScrolling: Binding<Bool>
private let scrollViewController: UIViewControllerType
// MARK: - Init
init(_ offset: Binding<CGPoint>, animationDuration: TimeInterval, showsScrollIndicator: Bool = true, axis: Axis = .vertical, onScale: ((CGFloat)->Void)? = nil, disableScroll: Bool = false, forceRefresh: Bool = false, stopScrolling: Binding<Bool> = .constant(false), @ViewBuilder content: @escaping () -> Content) {
self.offset = offset
self.onScale = onScale
self.animationDuration = animationDuration
self.content = content
self.showsScrollIndicator = showsScrollIndicator
self.axis = axis
self.disableScroll = disableScroll
self.forceRefresh = forceRefresh
self.stopScrolling = stopScrolling
self.scrollViewController = UIScrollViewController(rootView: self.content(), offset: self.offset, axis: self.axis, onScale: self.onScale)
}
// MARK: - Updates
func makeUIViewController(context: UIViewControllerRepresentableContext<Self>) -> UIViewControllerType {
self.scrollViewController
}
func updateUIViewController(_ viewController: UIViewControllerType, context: UIViewControllerRepresentableContext<Self>) {
viewController.scrollView.showsVerticalScrollIndicator = self.showsScrollIndicator
viewController.scrollView.showsHorizontalScrollIndicator = self.showsScrollIndicator
viewController.updateContent(self.content)
let duration: TimeInterval = self.duration(viewController)
let newValue: CGPoint = self.offset.wrappedValue
viewController.scrollView.isScrollEnabled = !self.disableScroll
if self.stopScrolling.wrappedValue {
viewController.scrollView.setContentOffset(viewController.scrollView.contentOffset, animated:false)
return
}
guard duration != .zero else {
viewController.scrollView.contentOffset = newValue
return
}
UIView.animate(withDuration: duration, delay: 0, options: [.allowUserInteraction, .curveEaseInOut, .beginFromCurrentState], animations: {
viewController.scrollView.contentOffset = newValue
}, completion: nil)
}
func makeCoordinator() -> Coordinator {
Coordinator(self.scrollViewController.scrollView, offset: self.offset)
}
//Calcaulte max offset
private func newContentOffset(_ viewController: UIViewControllerType, newValue: CGPoint) -> CGPoint {
let maxOffsetViewFrame: CGRect = viewController.view.frame
let maxOffsetFrame: CGRect = viewController.hostingController.view.frame
let maxOffsetX: CGFloat = maxOffsetFrame.maxX - maxOffsetViewFrame.maxX
let maxOffsetY: CGFloat = maxOffsetFrame.maxY - maxOffsetViewFrame.maxY
return CGPoint(x: min(newValue.x, maxOffsetX), y: min(newValue.y, maxOffsetY))
}
//Calculate animation speed
private func duration(_ viewController: UIViewControllerType) -> TimeInterval {
var diff: CGFloat = 0
switch axis {
case .horizontal:
diff = abs(viewController.scrollView.contentOffset.x - self.offset.wrappedValue.x)
default:
diff = abs(viewController.scrollView.contentOffset.y - self.offset.wrappedValue.y)
}
if diff == 0 {
return .zero
}
let percentageMoved = diff / UIScreen.main.bounds.height
return self.animationDuration * min(max(TimeInterval(percentageMoved), 0.25), 1)
}
// MARK: - Equatable
static func == (lhs: ScrollableView, rhs: ScrollableView) -> Bool {
return !lhs.forceRefresh && lhs.forceRefresh == rhs.forceRefresh
}
}
final class UIScrollViewController<Content: View> : UIViewController, ObservableObject {
// MARK: - Properties
var offset: Binding<CGPoint>
var onScale: ((CGFloat)->Void)?
let hostingController: UIHostingController<Content>
private let axis: Axis
lazy var scrollView: UIScrollView = {
let scrollView = UIScrollView()
scrollView.translatesAutoresizingMaskIntoConstraints = false
scrollView.canCancelContentTouches = true
scrollView.delaysContentTouches = true
scrollView.scrollsToTop = false
scrollView.backgroundColor = .clear
if self.onScale != nil {
scrollView.addGestureRecognizer(UIPinchGestureRecognizer(target: self, action: #selector(self.onGesture)))
}
return scrollView
}()
@objc func onGesture(gesture: UIPinchGestureRecognizer) {
self.onScale?(gesture.scale)
}
// MARK: - Init
init(rootView: Content, offset: Binding<CGPoint>, axis: Axis, onScale: ((CGFloat)->Void)?) {
self.offset = offset
self.hostingController = UIHostingController<Content>(rootView: rootView)
self.hostingController.view.backgroundColor = .clear
self.axis = axis
self.onScale = onScale
super.init(nibName: nil, bundle: nil)
}
// MARK: - Update
func updateContent(_ content: () -> Content) {
self.hostingController.rootView = content()
self.scrollView.addSubview(self.hostingController.view)
var contentSize: CGSize = self.hostingController.view.intrinsicContentSize
switch axis {
case .vertical:
contentSize.width = self.scrollView.frame.width
case .horizontal:
contentSize.height = self.scrollView.frame.height
}
self.hostingController.view.frame.size = contentSize
self.scrollView.contentSize = contentSize
self.view.updateConstraintsIfNeeded()
self.view.layoutIfNeeded()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(self.scrollView)
self.createConstraints()
self.view.setNeedsUpdateConstraints()
self.view.updateConstraintsIfNeeded()
self.view.layoutIfNeeded()
}
// MARK: - Constraints
fileprivate func createConstraints() {
NSLayoutConstraint.activate([
self.scrollView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor),
self.scrollView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor),
self.scrollView.topAnchor.constraint(equalTo: self.view.topAnchor),
self.scrollView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
])
}
}
Then in your code snippet you can use it like this:
import SwiftUI
struct ContentView: View {
@State private var contentOffset: CGPoint = .zero
var body: some View {
ScrollableView(self.$contentOffset, animationDuration: 5.0) {
VStack {
Button("Scroll to") {
self.contentOffset = CGPoint(x: 0, y: (100 * 50))
}
ForEach(0..<100) { i in
Rectangle()
.frame(width: 200, height: 100)
.foregroundColor(.green)
.overlay(Text("\(i)").foregroundColor(.white).id(i))
}
.frame(maxWidth: .infinity)
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
You can set the animation duration, I have set it to 5 seconds, then calculate the offset you want to scroll depending in the row height, I set it to 100 * 50 cells.
When you tap in the button the view will scroll to index 50 in 5 seconds.
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