Container controller that hides both tab and navigation bars when scrolling.

TAMHidingBarsViewController.h

//
//  TAMHidingBarsViewController.h
//
//  Created by Vladislav Kartashov on 13/07/15.
//  Copyright (c) 2015 Vladislav Kartashov. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface TAMHidingBarsViewController : UIViewController <UINavigationControllerDelegate>
@property (nonatomic, readonly) BOOL navigationBarIsHidden;
@property (nonatomic) BOOL hideTabBar;
@property (nonatomic) BOOL enabled;

- (instancetype)initWithViewController:(UIViewController *)controller;

- (void)hideTabBarWithDuration:(NSTimeInterval)duration;
- (void)showNavigationBarWithDuration:(NSTimeInterval)duration;

- (void)showBars:(BOOL)animated;
- (void)hideBars:(BOOL)animated;

- (void)enableBarsHiding;
- (void)disableBarsHiding;

@property (nonatomic, copy) void(^willHideNavigationBarBlock)();
@property (nonatomic, copy) void(^willShowNavigationBarBlock)();
- (void)willHideNavigationBar;
- (void)didHideNavigationBar;
- (void)willShowNavigationBar;
- (void)didShowNavigationBar;
@end

TAMHidingBarsViewController.m

//
//  TAMHidingBarsViewController.m
//
//  Created by Vladislav Kartashov on 13/07/15.
//  Copyright (c) 2015 Vladislav Kartashov. All rights reserved.
//

#import "TAMHidingBarsViewController.h"
#import "TAMAppearance.h"
#import "XOGlobalVars.h"

@interface TAMHidingBarsViewController () <UIGestureRecognizerDelegate>
@property (nonatomic) UIViewController *rootViewController;
@property (nonatomic, weak) IBOutlet UIView *containerView;

@property (nonatomic) CGRect navigationBarFrame;
@property (nonatomic) CGRect statusBarFrame;
@property (nonatomic) CGRect tabBarFrame;

@property (nonatomic) CGPoint velocity;

@property (nonatomic) UIView *barItemsHidingView;

// bars are customised differently when navigation controller performs push with hidden navigation bar
@property (nonatomic) BOOL isBeingPushedAwayWithHiddenNavigationBar;
@property (nonatomic) CGPoint initialVelocity;
@end

@implementation TAMHidingBarsViewController

- (instancetype)initWithViewController:(UIViewController *)controller {
  self = [super initWithNibName:NSStringFromClass([self class]) bundle:nil];
  if (self) {
    _rootViewController = controller;
  }
  return self;
}

- (void)setTitle:(NSString *)title {
  // could not customize label's look via appearance proxy for some reason
  // this is a hack and it should be rewritten later
  UILabel *titleLabel = [[UILabel alloc] init];
  titleLabel.text = title;
  titleLabel.font = [UIFont boldSystemFontOfSize:17.0f];
  titleLabel.textColor = [UIColor tam_navigationBarTintColor];
  [titleLabel sizeToFit];
  self.navigationItem.titleView = titleLabel;
}

- (void)viewWillAppear:(BOOL)animated {
  [super viewWillAppear:animated];
  [self.navigationItem addObserver:self
                        forKeyPath:@"titleView"
                           options:NSKeyValueObservingOptionNew
                           context:nil];
  if ([XOGlobalVars sharedObject].aboutToShowModalProfile) {
    [XOGlobalVars sharedObject].aboutToShowModalProfile = NO;
    [self showBars:animated];
  }
}

- (void)viewWillDisappear:(BOOL)animated {
  [self.navigationItem removeObserver:self forKeyPath:@"titleView"];
  if ([XOGlobalVars sharedObject].aboutToShowModalProfile) {
    //[XOGlobalVars sharedObject].aboutToShowModalProfile = NO;
  }
  else {
    [self showBars:animated];
  }
}

- (void)viewDidLoad {
  [super viewDidLoad];
  
  if (self.rootViewController) {
    [self addChildViewController:self.rootViewController];
    [self.containerView addSubview:self.rootViewController.view];
    [self.rootViewController didMoveToParentViewController:self];
  }
  
  [self setVelocity:CGPointMake(1.0f, 1.0f)];
  [self setEnabled:YES];
  [self setupBars];
  
  UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
  [self.view addGestureRecognizer:panGesture];
  panGesture.delegate = self;
  
  self.navigationController.delegate = self;
  
  [self showNavigationBarWithDuration:0.0f];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
  if ([self navigationBarIsHidden]) {
    self.navigationItem.titleView.alpha = 0.0f;
  }
}

- (void)viewDidLayoutSubviews {
  [super viewDidLayoutSubviews];
  self.rootViewController.view.frame = self.containerView.bounds;
  self.barItemsHidingView.frame = self.navigationController.navigationBar.bounds;
  [self updateContainerOffsets];
}

- (void)updateContainerOffsets {
  CGRect frame = self.containerView.frame;
  
  CGFloat topOffset = self.navigationBarFrame.origin.y + self.navigationBarFrame.size.height;
  CGFloat bottomOffset = self.view.bounds.size.height - self.tabBarFrame.origin.y;
  
  if (self.isBeingPushedAwayWithHiddenNavigationBar) {
    self.isBeingPushedAwayWithHiddenNavigationBar = NO;
    
    frame.size.height = self.view.bounds.size.height - bottomOffset;
    frame.origin.y = self.navigationBarFrame.origin.y;
    
  } else {
    
    frame.size.height = self.view.bounds.size.height - topOffset - (self.hideTabBar ? 0 : bottomOffset);
    frame.origin.y = topOffset;
  }
  
  frame.size.width = self.view.bounds.size.width;
  self.containerView.frame = frame;
  [self.view layoutIfNeeded];
}

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
  BOOL isBeingPushed = viewController != self;
  
  if (isBeingPushed && self.navigationBarIsHidden) {
    self.isBeingPushedAwayWithHiddenNavigationBar = YES;
    [self showNavigationBarWithDuration:0.0f];
    // we hide tab bar to make sure system won't show it up.
    // this is not (!) related to hidesBottomBarWhenPushed property
    [self hideTabBarWithDuration:0.0f];
  }
}

- (void)setupBars {
  self.extendedLayoutIncludesOpaqueBars = YES;
  self.automaticallyAdjustsScrollViewInsets = NO;

  self.edgesForExtendedLayout = UIRectEdgeTop | UIRectEdgeBottom;
  
  self.barItemsHidingView = [[UIView alloc] initWithFrame:CGRectZero];
  self.barItemsHidingView.backgroundColor = [UIColor tam_navigationBarColor];
  self.barItemsHidingView.alpha = 0.0f;
  [self.navigationController.navigationBar addSubview:self.barItemsHidingView];
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
  return YES;
}

#define VELOCITY_FACTOR 0.0025f
#define MIN_SHOW_VELOCITY 2.0f
#define MIN_HIDE_VELOCITY -1.0f

- (void)pan:(UIPanGestureRecognizer *)gesture {
  if (!self.enabled) {
    return;
  }
  
  self.velocity = [gesture velocityInView:self.view];
  CGPoint velocity = [gesture velocityInView:self.view];
  CGFloat offset = velocity.y * VELOCITY_FACTOR;

  switch (gesture.state) {
    case UIGestureRecognizerStateCancelled:
    case UIGestureRecognizerStateEnded: {
      CGPoint endVelocity = velocity;
      if (self.initialVelocity.y < 0 && self.navigationBarIsHidden) {
        endVelocity = self.initialVelocity;
      }
      [self endBarsAnimationWithVelocity:endVelocity];
    }
    case UIGestureRecognizerStateBegan:
      self.initialVelocity = velocity;
      return;
    case UIGestureRecognizerStateChanged:
      if (self.initialVelocity.y > 0 && self.navigationBarIsHidden) {
        return;
      }
    default:
      break;
  }
  
  CGFloat statusBarHeight = [[UIApplication sharedApplication] statusBarFrame].size.height;
  
  CGRect tabBarUpdatedFrame = self.tabBarFrame;
  CGRect navBarUpdatedFrame = self.navigationController.navigationBar.frame;
  
  tabBarUpdatedFrame.origin.y -= self.hideTabBar ? 0 : offset;
  navBarUpdatedFrame.origin.y += offset;
  
  
  if (navBarUpdatedFrame.origin.y < statusBarHeight && navBarUpdatedFrame.origin.y > 0 - navBarUpdatedFrame.size.height + statusBarHeight) {
    self.navigationController.navigationBar.frame = navBarUpdatedFrame;
    
    CGRect frame = self.containerView.frame;
    frame.origin.y += offset;
    frame.size.height -= self.hideTabBar ? offset : 0;
    self.containerView.frame = frame;
    
    
    CGFloat framePercentageHidden = ((self.statusBarFrame.size.height - self.navigationBarFrame.origin.y) / (self.navigationBarFrame.size.height - 1));
    [self setBarItemsOpacity:1 - framePercentageHidden];
  }
  
  if (tabBarUpdatedFrame.origin.y < self.view.bounds.size.height && tabBarUpdatedFrame.origin.y > self.view.bounds.size.height - self.tabBarController.tabBar.bounds.size.height) {
    self.tabBarController.tabBar.frame = tabBarUpdatedFrame;
    
    CGRect frame = self.containerView.frame;
    frame.size.height = self.view.bounds.size.height - (self.navigationBarFrame.origin.y + self.navigationBarFrame.size.height) - (self.view.bounds.size.height - self.tabBarFrame.origin.y);
    self.containerView.frame = frame;
  }
  
  [self.view updateConstraints];
}

- (void)setBarItemsOpacity:(CGFloat)opacity {
  UINavigationItem *navigationItem = self.navigationController.navigationBar.topItem;
  
  
  NSArray *leftButtonItems = navigationItem.leftBarButtonItems ? navigationItem.leftBarButtonItems : @[];
  NSArray *barButtonItems = [leftButtonItems arrayByAddingObjectsFromArray:navigationItem.rightBarButtonItems];
  for (UIBarButtonItem *item in barButtonItems) {
    self.barItemsHidingView.alpha = 1 - opacity;
    [item setTintColor:[item.tintColor colorWithAlphaComponent:opacity]];
    item.customView.alpha = opacity;
  }
  
  navigationItem.titleView.alpha = opacity;
}

#define MIN_VELOCITY 300.0f
#define DURATION 0.2f

- (void)endBarsAnimationWithVelocity:(CGPoint)velocity {
  if (self.initialVelocity.y > 0 && self.navigationBarIsHidden && velocity.y < MIN_VELOCITY) {
    return;
  }
  
  CGFloat duration = fabsf(DURATION);
  if (velocity.y < 0) {
    
    [self hideNavigationBarWithDuration:duration];
    [self hideTabBarWithDuration:duration];
    
    [UIView animateWithDuration:duration
                          delay:0.0f
                        options:UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction
                     animations:^{
                       [self updateContainerOffsets];
                     }
                     completion:nil];
  } else {
    
    [self showNavigationBarWithDuration:duration];
    [self showTabBarWithDuration:duration];
    
    [UIView animateWithDuration:duration
                          delay:0.0f
                        options:UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction
                     animations:^{
                       [self updateContainerOffsets];
                     }
                     completion:nil];
  }
}

- (void)hideTabBarWithDuration:(NSTimeInterval)duration {
  [UIView animateWithDuration:duration
                        delay:0.0f
                      options:UIViewAnimationOptionCurveLinear
                   animations:^{
                     CGRect tabBarFrame = self.tabBarFrame;
                     tabBarFrame.origin.y = self.view.bounds.size.height;
                     self.tabBarController.tabBar.frame = tabBarFrame;

                     [self updateContainerOffsets];
                   }
                   completion:nil];
}

- (void)showTabBarWithDuration:(NSTimeInterval)duration {
  [UIView animateWithDuration:duration
                        delay:0.0f
                      options:UIViewAnimationOptionCurveLinear
                   animations:^{
                     CGRect tabBarFrame = self.tabBarFrame;
                     tabBarFrame.origin.y = self.view.bounds.size.height - tabBarFrame.size.height;
                     
                     self.tabBarController.tabBar.frame = tabBarFrame;

                     [self updateContainerOffsets];
                   }
                   completion:nil];
}

- (void)hideNavigationBarWithDuration:(NSTimeInterval)duration {
  [self willHideNavigationBar];
  [UIView animateWithDuration:duration
                        delay:0.0f
                      options:UIViewAnimationOptionCurveLinear
                   animations:^{
                     CGRect navBarFrame = self.navigationController.navigationBar.frame;
                     navBarFrame.origin.y = self.statusBarFrame.size.height - self.navigationBarFrame.size.height;
                     
                     [self.navigationController.navigationBar setFrame:navBarFrame];
                     [self setBarItemsOpacity:0.0f];

                     [self updateContainerOffsets];
                   }
                   completion:^(BOOL finished) {
                     if (finished) {
                       [self didHideNavigationBar];
                     }
                   }];
}

- (void)showNavigationBarWithDuration:(NSTimeInterval)duration {
  [self willShowNavigationBar];
  [UIView animateWithDuration:duration
                        delay:0.0f
                      options:UIViewAnimationOptionCurveLinear
                   animations:^{
                     CGRect navBarFrame = self.navigationBarFrame;
                     navBarFrame.origin.y = self.statusBarFrame.size.height;
                     
                     [self.navigationController.navigationBar setFrame:navBarFrame];
                     // if items are visible when self is pushed away by navigation controller
                     // animations look a bit glitchy. so we keep them hidden
                     if (!self.isBeingPushedAwayWithHiddenNavigationBar) {
                       [self setBarItemsOpacity:1.0f];
                     }

                     [self updateContainerOffsets];
                   }
                   completion:^(BOOL finished) {
                     if (finished) {
                       [self didShowNavigationBar];
                     }
                   }];
}

- (void)showBars:(BOOL)animated {
  if (self.navigationBarIsHidden) {
    [self showNavigationBarWithDuration:animated ? DURATION : 0.0f];
    [self showTabBarWithDuration:animated ? DURATION : 0.0f];
  }
}

- (void)hideBars:(BOOL)animated {
  if (!self.navigationBarIsHidden) {
    [self hideNavigationBarWithDuration:animated ? DURATION : 0.0f];
    [self hideTabBarWithDuration:animated ? DURATION : 0.0f];
  }
}

- (CGRect)tabBarFrame {
  return self.tabBarController.tabBar.frame;
}

- (CGRect)navigationBarFrame {
  return self.navigationController.navigationBar.frame;
}

- (CGRect)statusBarFrame {
  return [[UIApplication sharedApplication] statusBarFrame];
}

- (void)enableBarsHiding {
  self.enabled = YES;
}

- (void)disableBarsHiding {
//  self.velocity.y > 0 ? [self showBars:NO] : [self hideBars:NO];
  self.enabled = NO;
}

- (BOOL)navigationBarIsHidden {
  return self.navigationBarFrame.origin.y < self.statusBarFrame.size.height - self.navigationBarFrame.size.height * 0.5f;
}

- (void)willHideNavigationBar {
  if (_willHideNavigationBarBlock) {
    _willHideNavigationBarBlock();
  }
}

- (void)willShowNavigationBar {
  if (_willShowNavigationBarBlock) {
    _willShowNavigationBarBlock();
  }
}

- (void)didHideNavigationBar {
  
}

- (void)didShowNavigationBar {
  
}


@end