Add Progressive Tab Scrolling Representation

GUITabPagerViewController/Classes/GUITabPagerViewController.h

@@ -15,6 +15,7 @@
 
 @property (weak, nonatomic) id<GUITabPagerDataSource> dataSource;
 @property (weak, nonatomic) id<GUITabPagerDelegate> delegate;
+@property (assign, nonatomic) BOOL isProgressive;
 
 - (void)reloadData;
 - (NSInteger)selectedIndex;

GUITabPagerViewController/Classes/GUITabPagerViewController.m

@@ -9,7 +9,10 @@
 #import "GUITabPagerViewController.h"
 #import "GUITabScrollView.h"
 
-@interface GUITabPagerViewController () <GUITabScrollDelegate, UIPageViewControllerDataSource, UIPageViewControllerDelegate>
+@interface GUITabPagerViewController () <GUITabScrollDelegate, UIPageViewControllerDataSource, UIPageViewControllerDelegate, UIScrollViewDelegate>
+{
+  BOOL tapped;
+}
 
 @property (strong, nonatomic) UIPageViewController *pageViewController;
 @property (strong, nonatomic) GUITabScrollView *header;
@@ -37,9 +40,13 @@ - (void)viewDidLoad {
     if ([view isKindOfClass:[UIScrollView class]]) {
       [(UIScrollView *)view setCanCancelContentTouches:YES];
       [(UIScrollView *)view setDelaysContentTouches:NO];
+      [(UIScrollView *)view setDelegate:self];
     }
   }
 
+  tapped = false;
+  self.isProgressive = YES;
+
   [[self pageViewController] setDataSource:self];
   [[self pageViewController] setDelegate:self];
 
@@ -50,6 +57,7 @@ - (void)viewDidLoad {
 
 - (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
   [self reloadTabs];
+  [self selectTabbarIndex:self.selectedIndex];
 }
 
 - (void)didReceiveMemoryWarning {
@@ -72,12 +80,14 @@ - (UIViewController *)pageViewController:(UIPageViewController *)pageViewControl
 #pragma mark - Page View Delegate
 
 - (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers {
-  NSInteger index = [[self viewControllers] indexOfObject:pendingViewControllers[0]];
-  [[self header] animateToTabAtIndex:index];
-
-  if ([[self delegate] respondsToSelector:@selector(tabPager:willTransitionToTabAtIndex:)]) {
-    [[self delegate] tabPager:self willTransitionToTabAtIndex:index];
-  }
+    if (!self.isProgressive) {
+        NSInteger index = [[self viewControllers] indexOfObject:pendingViewControllers[0]];
+        [[self header] animateToTabAtIndex:index];
+
+        if ([[self delegate] respondsToSelector:@selector(tabPager:willTransitionToTabAtIndex:)]) {
+            [[self delegate] tabPager:self willTransitionToTabAtIndex:index];
+        }
+    }
 }
 
 - (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
@@ -96,7 +106,7 @@ - (void)tabScrollView:(GUITabScrollView *)tabScrollView didSelectTabAtIndex:(NSI
     if ([[self delegate] respondsToSelector:@selector(tabPager:willTransitionToTabAtIndex:)]) {
       [[self delegate] tabPager:self willTransitionToTabAtIndex:index];
     }
-
+    tapped = true;
     [[self pageViewController]  setViewControllers:@[[self viewControllers][index]]
                                          direction:(index > [self selectedIndex]) ? UIPageViewControllerNavigationDirectionForward : UIPageViewControllerNavigationDirectionReverse
                                           animated:YES
@@ -217,6 +227,34 @@ - (void)reloadTabs {
   [[self view] addSubview:[self header]];
 }
 
+#pragma mark - UIScrollViewDelegate
+
+- (void)scrollViewDidScroll:(UIScrollView *)scrollView
+{
+  if (self.isProgressive) {
+    CGPoint offset = scrollView.contentOffset;
+    float progress = 0;
+    NSInteger fromIndex = self.selectedIndex;
+    NSInteger toIndex = -1;
+    progress = (offset.x - self.view.bounds.size.width) / self.view.bounds.size.width;
+    if (progress > 0) {
+      if (fromIndex < [[self viewControllers] count] - 1) {
+        toIndex = fromIndex + 1;
+      }
+    }
+    else {
+      if (fromIndex > 0) {
+        toIndex = fromIndex - 1;
+      }
+    }
+    if (!tapped) {
+      [[self header] animateFromTabAtIndex:fromIndex toTabAtIndex:toIndex withProgress:progress];
+    }
+    else if (fabs(progress) >= 0.999999 || fabs(progress) <= 0.000001)
+      tapped = false;
+  }
+}
+
 #pragma mark - Public Methods
 
 - (void)selectTabbarIndex:(NSInteger)index {

GUITabPagerViewController/Classes/GUITabScrollView.h

@@ -19,6 +19,8 @@
 
 - (void)animateToTabAtIndex:(NSInteger)index;
 - (void)animateToTabAtIndex:(NSInteger)index animated:(BOOL)animated;
+- (void)animateFromTabAtIndex:(NSInteger)fromIndex toTabAtIndex:(NSInteger)toIndex withProgress:(float)progress;
+
 
 @end
 

GUITabPagerViewController/Classes/GUITabScrollView.m

@@ -168,11 +168,36 @@ - (void)animateToTabAtIndex:(NSInteger)index animated:(BOOL)animated {
                      }];
 }
 
+- (void)animateFromTabAtIndex:(NSInteger)fromIndex toTabAtIndex:(NSInteger)toIndex withProgress:(float)progress {
+    if (fromIndex != -1 && toIndex != -1) {
+        CGFloat x = [[self tabViews][0] frame].origin.x - 5;
+        CGFloat w = [[self tabViews][fromIndex] frame].size.width + 10;
+        for (int i = 0; i < fromIndex; i++) {
+            x += [[self tabViews][i] frame].size.width + 10;
+        }
+        CGFloat p = x - (self.frame.size.width - w) / 2;
+        x += fabs([[self tabViews][toIndex] frame].origin.x - [[self tabViews][fromIndex] frame].origin.x) * progress;
+
+
+        w += ([[self tabViews][toIndex] frame].size.width - [[self tabViews][fromIndex] frame].size.width) * fabs(progress);
+
+
+        CGFloat min = 0;
+        CGFloat max = MAX(0, self.contentSize.width - self.frame.size.width);
+
+        [self setContentOffset:CGPointMake(MAP(p, min, max), 0)];
+        [[self tabIndicatorDisplacement] setConstant:x];
+        [[self tabIndicatorWidth] setConstant:w];
+        [self layoutIfNeeded];
+
+    }
+}
+
 - (void)tabTapHandler:(UITapGestureRecognizer *)gestureRecognizer {
   if ([[self tabScrollDelegate] respondsToSelector:@selector(tabScrollView:didSelectTabAtIndex:)]) {
     NSInteger index = [[gestureRecognizer view] tag];
-    [[self tabScrollDelegate] tabScrollView:self didSelectTabAtIndex:index];
     [self animateToTabAtIndex:index];
+    [[self tabScrollDelegate] tabScrollView:self didSelectTabAtIndex:index];
   }
 }