fix(ios): emit onPageSelected for vertical orientation and initialPage

Author: MrRefactor

ios/PagerScrollDelegate.swift

@@ -7,6 +7,8 @@ class PagerScrollDelegate: NSObject, UIScrollViewDelegate, UICollectionViewDeleg
   weak var originalDelegate: UICollectionViewDelegate?
   weak var delegate: PagerViewProviderDelegate?
   var orientation: UICollectionView.ScrollDirection = .horizontal
+  var lastSelectedPage: Int = -1
+  var isProgrammaticScroll: Bool = false
 
   private let handledSelectors: Set<Selector> = [
     #selector(scrollViewDidScroll(_:)),
@@ -45,21 +47,45 @@ class PagerScrollDelegate: NSObject, UIScrollViewDelegate, UICollectionViewDeleg
   }
 
   func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
+    emitPageSelectedIfNeeded(scrollView)
     delegate?.onPageScrollStateChanged(state: .idle)
     originalDelegate?.scrollViewDidEndDecelerating?(scrollView)
   }
-  
+
   func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
+    emitPageSelectedIfNeeded(scrollView)
     delegate?.onPageScrollStateChanged(state: .idle)
     originalDelegate?.scrollViewDidEndScrollingAnimation?(scrollView)
   }
-  
+
   func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
     if !decelerate {
+      emitPageSelectedIfNeeded(scrollView)
       delegate?.onPageScrollStateChanged(state: .idle)
     }
     originalDelegate?.scrollViewDidEndDragging?(scrollView, willDecelerate: decelerate)
   }
+
+  private func emitPageSelectedIfNeeded(_ scrollView: UIScrollView) {
+    // Skip during programmatic navigation — .onChange handles that
+    if isProgrammaticScroll {
+      isProgrammaticScroll = false
+      return
+    }
+
+    let isHorizontal = orientation == .horizontal
+    let pageSize = isHorizontal ? scrollView.frame.width : scrollView.frame.height
+    let contentOffset = isHorizontal ? scrollView.contentOffset.x : scrollView.contentOffset.y
+
+    guard pageSize > 0 else { return }
+
+    let page = Int(round(contentOffset / pageSize))
+
+    if page != lastSelectedPage {
+      lastSelectedPage = page
+      delegate?.onPageSelected(position: page)
+    }
+  }
 
   func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
     originalDelegate?.collectionView?(collectionView, didEndDisplaying: cell, forItemAt: indexPath)

ios/PagerView.swift

@@ -44,7 +44,11 @@ struct PagerView: View {
       }
     }
     .onChange(of: props.currentPage) { newValue in
-      delegate?.onPageSelected(position: newValue)
+      if scrollDelegate.lastSelectedPage != newValue {
+        scrollDelegate.lastSelectedPage = newValue
+        scrollDelegate.isProgrammaticScroll = true
+        delegate?.onPageSelected(position: newValue)
+      }
     }
     .onChange(of: props.scrollEnabled) { newValue in
       collectionView?.isScrollEnabled = newValue

ios/RNCPagerViewComponentView.mm

@@ -67,6 +67,12 @@ - (void)updateProps:(const facebook::react::Props::Shared &)props oldProps:(cons
 
   if (_pagerViewProvider.currentPage == -1) {
      _pagerViewProvider.currentPage = newScreenProps.initialPage;
+     // Defer initial onPageSelected until event emitter is available
+     if (newScreenProps.initialPage > 0) {
+       dispatch_async(dispatch_get_main_queue(), ^{
+         [self onPageSelectedWithPosition:newScreenProps.initialPage];
+       });
+     }
    }
 
   if (oldScreenProps.scrollEnabled != newScreenProps.scrollEnabled) {
@@ -103,16 +109,19 @@ - (void)updateProps:(const facebook::react::Props::Shared &)props oldProps:(cons
 
 - (void)onPageScrollWithData:(OnPageScrollEventData *)data {
   const auto eventEmitter = [self pagerEventEmitter];
+  if (!eventEmitter) return;
   [self sendScrollEventsForPosition:data.position offset:data.offset];
 }
 
 - (void)onPageSelectedWithPosition:(NSInteger)position {
   const auto eventEmitter = [self pagerEventEmitter];
+  if (!eventEmitter) return;
   eventEmitter->onPageSelected(RNCViewPagerEventEmitter::OnPageSelected{.position =  static_cast<double>(position)});
 }
 
 - (void)onPageScrollStateChangedWithState:(enum PageScrollState)state {
   const auto eventEmitter = [self pagerEventEmitter];
+  if (!eventEmitter) return;
 
   RNCViewPagerEventEmitter::OnPageScrollStateChangedPageScrollState scrollState;