feat: add new scroll view extension to read content offset

Sources/ExtensionKit/SwiftUI/ScrollViewOffSetReader.swift

@@ -0,0 +1,97 @@
+import SwiftUI
+import UIKit
+
+/// Hosting controller that updates the scroll view offset (x,y)
+class ScrollViewOffSetReader<Content>: UIHostingController<Content> where Content: View {
+
+    var offset: Binding<CGFloat>
+    let isOffsetX: Bool
+    var showed = false
+    var sv: UIScrollView?
+
+    init(offset: Binding<CGFloat>, isOffsetX: Bool, rootView: Content) {
+        self.offset = offset
+        self.isOffsetX = isOffsetX
+        super.init(rootView: rootView)
+    }
+
+    @objc dynamic required init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    override func viewDidAppear(_ animated: Bool) {
+        if showed {
+            return
+        }
+        showed = true
+
+        sv = findScrollView(in: view)
+
+        sv?.addObserver(self,
+                        forKeyPath: #keyPath(UIScrollView.contentOffset),
+                        options: [.old, .new],
+                        context: nil)
+
+        scroll(to: offset.wrappedValue, animated: false)
+
+        super.viewDidAppear(animated)
+    }
+
+    func scroll(to position: CGFloat, animated: Bool = true) {
+        if let s = sv {
+            if position != (self.isOffsetX ? s.contentOffset.x : s.contentOffset.y) {
+                let offset = self.isOffsetX ? CGPoint(x: position, y: 0) : CGPoint(x: 0, y: position)
+                sv?.setContentOffset(offset, animated: animated)
+            }
+        }
+    }
+
+    override func observeValue(forKeyPath keyPath: String?,
+                               of object: Any?,
+                               change: [NSKeyValueChangeKey: Any]?,
+                               context: UnsafeMutableRawPointer?) {
+        if keyPath == #keyPath(UIScrollView.contentOffset) {
+            if let s = self.sv {
+                DispatchQueue.main.async {
+                    self.offset.wrappedValue = self.isOffsetX ? s.contentOffset.x : s.contentOffset.y
+                }
+            }
+        }
+    }
+
+    func findScrollView(in view: UIView?) -> UIScrollView? {
+        if view?.isKind(of: UIScrollView.self) ?? false {
+            return view as? UIScrollView
+        }
+
+        for subview in view?.subviews ?? [] {
+            if let sv = findScrollView(in: subview) {
+                return sv
+            }
+        }
+
+        return nil
+    }
+}
+
+struct ScrollViewOffSetReaderRepresentable<Content>: UIViewControllerRepresentable where Content: View {
+
+    var offset: Binding<CGFloat>
+    let isOffsetX: Bool
+    let content: Content
+
+    init(offset: Binding<CGFloat>, isOffsetX: Bool, @ViewBuilder content: @escaping () -> Content) {
+
+        self.offset = offset
+        self.isOffsetX = isOffsetX
+        self.content = content()
+    }
+
+    func makeUIViewController(context: Context) -> ScrollViewOffSetReader<Content> {
+        ScrollViewOffSetReader(offset: offset, isOffsetX: isOffsetX, rootView: content)
+    }
+
+    func updateUIViewController(_ uiViewController: ScrollViewOffSetReader<Content>, context: Context) {
+        uiViewController.scroll(to: offset.wrappedValue, animated: true)
+    }
+}

Sources/ExtensionKit/SwiftUI/View.swift

@@ -418,4 +418,18 @@ public extension View {
     func onReceive<P: Publisher>(_ publisher: P, assignTo binding: Binding<P.Output?>) -> some View where P.Failure == Never {
         onReceive(publisher) { binding.wrappedValue = $0 }
     }
+
+    /// Get the scroll view content offset X
+    /// - Parameter offsetX: Binding for offset
+    /// - Returns: View
+    func scrollOffsetX(_ offsetX: Binding<CGFloat>) -> some View {
+        ScrollViewOffSetReaderRepresentable(offset: offsetX, isOffsetX: true) { self }
+    }
+
+    /// Get the scroll view content offset Y
+    /// - Parameter offsetY: Binding for offset
+    /// - Returns: View
+    func scrollOffsetY(_ offsetY: Binding<CGFloat>) -> some View {
+        ScrollViewOffSetReaderRepresentable(offset: offsetY, isOffsetX: false) { self }
+    }
 }