feat: implement onPageScrollStateChanged

Author: Piotr Trocki

ios/ReactNativePageView.h

@@ -21,6 +21,8 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic) UIPageViewControllerNavigationOrientation orientation;
 @property(nonatomic, copy) RCTBubblingEventBlock onPageSelected;
 @property(nonatomic, copy) RCTBubblingEventBlock onPageScroll;
+@property(nonatomic, copy) RCTBubblingEventBlock onPageScrollStateChanged;
+
 
 - (void)goTo:(NSNumber *)index animated:(BOOL)animated;
 - (void)shouldScroll:(BOOL)scrollEnabled;

ios/ReactNativePageView.m

@@ -279,6 +279,18 @@ - (UIPageControl *)createPageIndicator:(UIView *)parentView {
 
 #pragma mark - UIScrollViewDelegate
 
+- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
+     _onPageScrollStateChanged(@{@"pageScrollState": @"dragging"});
+}
+
+- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
+    _onPageScrollStateChanged(@{@"pageScrollState": @"settling"});
+}
+
+- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
+    _onPageScrollStateChanged(@{@"pageScrollState": @"idle"});
+}
+
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
     CGPoint point = scrollView.contentOffset;
     float offset = (point.x - self.frame.size.width)/self.frame.size.width;

ios/ReactViewPagerManager.m

@@ -14,6 +14,7 @@ @implementation ReactViewPagerManager
 RCT_EXPORT_VIEW_PROPERTY(orientation, UIPageViewControllerNavigationOrientation)
 RCT_EXPORT_VIEW_PROPERTY(onPageSelected, RCTBubblingEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onPageScroll, RCTBubblingEventBlock)
+RCT_EXPORT_VIEW_PROPERTY(onPageScrollStateChanged, RCTBubblingEventBlock)
 
 - (void) goToPage
                   : (nonnull NSNumber *)reactTag index