Add API for users to check and be notified of scrolling state

JTCalendar/JTCalendarDelegate.h

@@ -61,11 +61,21 @@
  */
 - (void)calendarDidLoadPreviousPage:(JTCalendarManager *)calendar;
 
+/**
+ *  Indicates the previous page finished scrolling after becoming the current page.
+ */
+- (void)calendarDidFinishScrollingToPreviousPage:(JTCalendarManager *)calendar;
+
 /*!
  * Indicate the next page became the current page.
  */
 - (void)calendarDidLoadNextPage:(JTCalendarManager *)calendar;
 
+/**
+ *  Indicates the next page finished scrolling after becoming the current page.
+ */
+- (void)calendarDidFinishScrollingToNextPage:(JTCalendarManager *)calendar;
+
 /*!
  * Provide a view conforming to `JTCalendarPage` protocol, used as page for the contentView.
  * Return an instance of `JTCalendarPageView` by default.

JTCalendar/Managers/JTCalendarScrollManager.h

@@ -27,5 +27,8 @@
 
 - (void)updateMenuContentOffset:(CGFloat)percentage pageMode:(NSUInteger)pageMode;
 - (void)updateHorizontalContentOffset:(CGFloat)percentage;
+- (void)endDragging;
+- (void)endDecelerating;
+- (void)endHorizontalScrollingAnimation;
 
 @end

JTCalendar/Managers/JTCalendarScrollManager.m

@@ -39,4 +39,31 @@ - (void)updateHorizontalContentOffset:(CGFloat)percentage
     _horizontalContentView.contentOffset = CGPointMake(percentage * _horizontalContentView.contentSize.width, 0);
 }
 
+- (void)endDragging
+{
+    if(![_horizontalContentView.delegate respondsToSelector:@selector(scrollViewDidEndDragging:willDecelerate:)]){
+        return;
+    }
+
+    [_horizontalContentView.delegate scrollViewDidEndDragging:_horizontalContentView willDecelerate:NO];
+}
+
+- (void)endDecelerating
+{
+    if(![_horizontalContentView.delegate respondsToSelector:@selector(scrollViewDidEndDecelerating:)]){
+        return;
+    }
+
+    [_horizontalContentView.delegate scrollViewDidEndDecelerating:_horizontalContentView];
+}
+
+- (void)endHorizontalScrollingAnimation
+{
+    if(![_horizontalContentView.delegate respondsToSelector:@selector(scrollViewDidEndScrollingAnimation:)]){
+        return;
+    }
+
+    [_horizontalContentView.delegate scrollViewDidEndScrollingAnimation:_horizontalContentView];
+}
+
 @end

JTCalendar/Views/JTCalendarMenuView.h

@@ -17,6 +17,8 @@
 
 @property (nonatomic, readonly) UIScrollView *scrollView;
 
+@property (nonatomic, assign, readonly) BOOL scrolling;
+
 /*!
  * Must be call if override the class
  */

JTCalendar/Views/JTCalendarMenuView.m

@@ -78,6 +78,15 @@ - (void)layoutSubviews
     [self resizeViewsIfWidthChanged];
 }
 
+#pragma mark - Properties
+
+- (BOOL)scrolling
+{
+    return self.scrollView.dragging || self.scrollView.decelerating;
+}
+
+#pragma mark - UIScrollViewDelegate
+
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
     if(_scrollView.contentSize.width <= 0){
@@ -87,6 +96,25 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView
     [_manager.scrollManager updateHorizontalContentOffset:(_scrollView.contentOffset.x / _scrollView.contentSize.width)];
 }
 
+- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
+{
+    if(!decelerate){
+        [_manager.scrollManager endDragging];
+    }
+}
+
+- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
+{
+    [_manager.scrollManager endDecelerating];
+}
+
+- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
+{
+    [_manager.scrollManager endHorizontalScrollingAnimation];
+}
+
+#pragma mark -
+
 - (void)resizeViewsIfWidthChanged
 {
     CGSize size = self.frame.size;

JTCalendar/Views/JTHorizontalCalendarView.h

@@ -15,6 +15,8 @@
 
 @property (nonatomic) NSDate *date;
 
+@property (nonatomic, assign, readonly) BOOL scrolling;
+
 /*!
  * Must be call if override the class
  */

JTCalendar/Views/JTHorizontalCalendarView.m

@@ -16,7 +16,13 @@ typedef NS_ENUM(NSInteger, JTCalendarPageMode) {
     JTCalendarPageModeCenterRight
 };
 
-@interface JTHorizontalCalendarView (){
+typedef NS_ENUM(NSInteger, JTCalendarScrollingDirection) {
+    JTCalendarScrollingDirectionNone = 0,
+    JTCalendarScrollingDirectionPrevious,
+    JTCalendarScrollingDirectionNext
+};
+
+@interface JTHorizontalCalendarView () <UIScrollViewDelegate> {
     CGSize _lastSize;
 
     UIView<JTCalendarPage> *_leftView;
@@ -26,6 +32,11 @@ @interface JTHorizontalCalendarView (){
     JTCalendarPageMode _pageMode;
 }
 
+// This class needs to hook into some of the UIScrollViewDelegate methods, so after it does that it will forward the messages on to the external delegate.
+@property (nonatomic, weak) id<UIScrollViewDelegate> externalDelegate;
+@property (nonatomic, assign) BOOL animatingOffset;
+@property (nonatomic, assign) JTCalendarScrollingDirection scrollingDirection;
+
 @end
 
 @implementation JTHorizontalCalendarView
@@ -60,8 +71,24 @@ - (void)commonInit
     self.showsVerticalScrollIndicator = NO;
     self.pagingEnabled = YES;
     self.clipsToBounds = YES;
+    // Deliberately using super here to avoid the overridden setter
+    [super setDelegate:self];
 }
 
+#pragma mark - Properties
+
+- (void)setDelegate:(id<UIScrollViewDelegate>)delegate
+{
+    self.externalDelegate = delegate;
+}
+
+- (BOOL)scrolling
+{
+    return self.dragging || self.decelerating || self.animatingOffset;
+}
+
+#pragma mark -
+
 - (void)layoutSubviews
 {
     [self resizeViewsIfWidthChanged];
@@ -232,6 +259,8 @@ - (void)loadPreviousPage
     // Update dayViews becuase current month changed
     [_rightView reload];
     [_centerView reload];
+
+    self.scrollingDirection = JTCalendarScrollingDirectionPrevious;
 
     if(_manager.delegate && [_manager.delegate respondsToSelector:@selector(calendarDidLoadPreviousPage:)]){
         [_manager.delegate calendarDidLoadPreviousPage:_manager];
@@ -313,7 +342,9 @@ - (void)loadNextPage
     // Update dayViews becuase current month changed
     [_leftView reload];
     [_centerView reload];
-
+
+    self.scrollingDirection = JTCalendarScrollingDirectionNext;
+
     if(_manager.delegate && [_manager.delegate respondsToSelector:@selector(calendarDidLoadNextPage:)]){
         [_manager.delegate calendarDidLoadNextPage:_manager];
     }
@@ -446,4 +477,63 @@ - (void)updateMenuDates
                                        nextDate:_rightView.date];
 }
 
+#pragma mark - UIScrollView
+
+- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated
+{
+    if(animated){
+        self.animatingOffset = YES;
+    }
+    [super setContentOffset:contentOffset animated:animated];
+}
+
+#pragma mark - UIScrollViewDelegate
+
+- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
+{
+    if(!decelerate){
+        [self notifyEndOfScrolling];
+    }
+
+    if(self.externalDelegate){
+        [self.externalDelegate scrollViewDidEndDragging:scrollView willDecelerate:decelerate];
+    }
+}
+
+- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
+{
+    [self notifyEndOfScrolling];
+
+    if(self.externalDelegate){
+        [self.externalDelegate scrollViewDidEndDecelerating:scrollView];
+    }
+}
+
+- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
+{
+    [self notifyEndOfScrolling];
+
+    if(self.externalDelegate){
+        [self.externalDelegate scrollViewDidEndScrollingAnimation:scrollView];
+    }
+}
+
+/**
+ *  Private helper for the above delegate methods
+ */
+- (void)notifyEndOfScrolling
+{
+    if(_manager.delegate){
+        if(self.scrollingDirection == JTCalendarScrollingDirectionPrevious && [_manager.delegate respondsToSelector:@selector(calendarDidFinishScrollingToPreviousPage:)]){
+            [_manager.delegate calendarDidFinishScrollingToPreviousPage:_manager];
+        }
+        else if(self.scrollingDirection == JTCalendarScrollingDirectionNext && [_manager.delegate respondsToSelector:@selector(calendarDidFinishScrollingToNextPage:)]){
+            [_manager.delegate calendarDidFinishScrollingToNextPage:_manager];
+        }
+    }
+
+    self.animatingOffset = NO;
+    self.scrollingDirection = JTCalendarScrollingDirectionNone;
+}
+
 @end