#6 Observe changes in contentSize and layout of ScrollStack via delegate

Author: malcommac

ScrollStackController.xcodeproj/project.xcworkspace/xcuserdata/daniele.xcuserdatad/UserInterfaceState.xcuserstate

@@ -8,7 +8,8 @@
 
 import UIKit
 
-class ViewController: UIViewController {
+class ViewController: UIViewController, ScrollStackControllerDelegate {
+
 
     @IBOutlet public var contentView: UIView!
 
@@ -28,13 +29,19 @@ class ViewController: UIViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
     }
+    
+    func scrollStackRowDidUpdateLayout(_ stackView: ScrollStack) {
+        debugPrint("New content insets \(stackView.contentSize.height)")
+    }
 
     override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
 
         stackController.view.frame = contentView.bounds
         contentView.addSubview(stackController.view)
 
+        
+        stackView.stackDelegate = self
         // Prepare content
 
         welcomeVC = WelcomeVC.create()
@@ -44,7 +51,6 @@ class ViewController: UIViewController {
         notesVC = NotesVC.create(delegate: self)
 
         stackView.addRows(controllers: [welcomeVC, notesVC, tagsVC, galleryVC,pricingVC], animated: false)
-
     }
 
     @IBAction public func addNewRow() {
@@ -78,6 +84,28 @@ class ViewController: UIViewController {
         let randomRow = Int.random(in: 0..<stackView.rows.count)
         stackView.scrollToRow(index: randomRow, at: .middle, animated: true)
     }
+    
+    
+    func scrollStackDidScroll(_ stackView: ScrollStack, offset: CGPoint) {
+        
+    }
+    
+    func scrollStackRowDidBecomeVisible(_ stackView: ScrollStack, row: ScrollStackRow, index: Int, state: ScrollStack.RowVisibility) {
+        
+    }
+    
+    func scrollStackRowDidBecomeHidden(_ stackView: ScrollStack, row: ScrollStackRow, index: Int, state: ScrollStack.RowVisibility) {
+        
+    }
+    
+    func scrollStackDidUpdateLayout(_ stackView: ScrollStack) {
+        
+    }
+    
+    func scrollStackContentSizeDidChange(_ stackView: ScrollStack, from oldValue: CGSize, to newValue: CGSize) {
+       // debugPrint("Content size did change from \(oldValue) to \(newValue)")
+    }
+    
 }
 
 extension ViewController: TagsVCProtocol {

ScrollStackControllerDemo/ViewController.swift

@@ -49,7 +49,10 @@ open class ScrollStack: UIScrollView, UIScrollViewDelegate {
     public static let defaultSeparatorColor = (UITableView().separatorColor ?? .clear)
     public static let defaultRowColor = UIColor.clear
     public static let defaultRowHighlightColor = UIColor(red: 0.85, green: 0.85, blue: 0.85, alpha: 1)
-
+    
+    /// Cached content size for did change content size callback in scrollstack delegate.
+    private var cachedContentSize: CGSize?
+    
     // MARK: Public Properties
 
     /// The direction that rows are laid out in the stack view and scrolling works.
@@ -953,4 +956,20 @@ open class ScrollStack: UIScrollView, UIScrollViewDelegate {
         dispatchRowsVisibilityChangesTo(stackDelegate)
     }
 
+    open override func layoutSubviews() {
+        super.layoutSubviews()
+        
+        guard let stackDelegate = stackDelegate else {
+            return
+        }
+        
+        stackDelegate.scrollStackDidUpdateLayout(self)
+        
+        if let oldContentSize = cachedContentSize, oldContentSize != self.contentSize {
+            stackDelegate.scrollStackContentSizeDidChange(self, from: oldContentSize, to: contentSize)
+        }
+        
+        cachedContentSize = self.contentSize
+    }
+    
 }

Sources/ScrollStackController/ScrollStack.swift

@@ -82,6 +82,19 @@ public protocol ScrollStackControllerDelegate: class {
     /// - Parameter state: state of the row.
     func scrollStackRowDidBecomeHidden(_ stackView: ScrollStack, row: ScrollStackRow, index: Int, state: ScrollStack.RowVisibility)
 
+    
+    /// This function is called when layout is updated (added, removed, hide or show one or more rows).
+    /// - Parameter stackView: target stack view.
+    func scrollStackDidUpdateLayout(_ stackView: ScrollStack)
+    
+    /// This function is called when content size of the stack did change (remove/add, hide/show rows).
+    ///
+    /// - Parameters:
+    ///   - stackView: target stack view
+    ///   - oldValue: old content size.
+    ///   - newValue: new content size.
+    func scrollStackContentSizeDidChange(_ stackView: ScrollStack, from oldValue: CGSize, to newValue: CGSize)
+    
 }
 
 // MARK: - ScrollStackRowHighlightable