components/Tabs/src/MDCTabBarViewController.m - external/github.com/material-components/material-components-ios - Git at Google

 /*
  Copyright 2017-present the Material Components for iOS authors. All Rights Reserved.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  */

 #import "MDCTabBarViewController.h"

 #import "MaterialShadowElevations.h"
 #import "MaterialShadowLayer.h"

 static NSString *const MDCTabBarViewControllerViewControllersKey =
     @"MDCTabBarViewControllerViewControllersKey";
 static NSString *const MDCTabBarViewControllerSelectedViewControllerKey =
     @"MDCTabBarViewControllerSelectedViewControllerKey";
 static NSString *const MDCTabBarViewControllerDelegateKey = @"MDCTabBarViewControllerDelegateKey";
 static NSString *const MDCTabBarViewControllerTabBarKey = @"MDCTabBarViewControllerTabBarKey";

 const CGFloat MDCTabBarViewControllerAnimationDuration = 0.3f;

 /**
  * View to host shadow for the tab bar.
  */
 @interface MDCTabBarShadowView : UIView
 @end

 @implementation MDCTabBarShadowView

 + (Class)layerClass {
   return [MDCShadowLayer class];
 }

 - (instancetype)initWithFrame:(CGRect)frame {
   self = [super initWithFrame:frame];
   if (self) {
     [self commonMDCTabBarShadowViewInitialization];
   }
   return self;
 }

 - (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
   self = [super initWithCoder:aDecoder];
   if (self) {
     [self commonMDCTabBarShadowViewInitialization];
   }
   return self;
 }

 - (void)commonMDCTabBarShadowViewInitialization {
   MDCShadowLayer *shadowLayer = (MDCShadowLayer *)self.layer;
   [shadowLayer setElevation:MDCShadowElevationMenu];
 }

 @end

 @interface MDCTabBarViewController ()

 @property(nonatomic, readwrite, nonnull) MDCTabBar *tabBar;

 @end

 @implementation MDCTabBarViewController {
   /** For showing/hiding, Animation needs to know where it wants to end up. */
   BOOL _tabBarWantsToBeHidden;
   MDCTabBarShadowView *_tabBarShadow;
 }

 - (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
   self = [super initWithCoder:aDecoder];
   if (self) {
     _viewControllers = [aDecoder decodeObjectOfClass:[NSArray class]
                                               forKey:MDCTabBarViewControllerViewControllersKey];
     self.selectedViewController =
         [aDecoder decodeObjectOfClass:[UIViewController class]
                                forKey:MDCTabBarViewControllerSelectedViewControllerKey];
     _tabBar = [aDecoder decodeObjectOfClass:[MDCTabBar class]
                                      forKey:MDCTabBarViewControllerTabBarKey];
     _delegate = [aDecoder decodeObjectForKey:MDCTabBarViewControllerDelegateKey];
     [self commonInit];
   }
   return self;
 }

 - (instancetype)init {
   self = [super init];
   if (self) {
     [self commonInit];
   }
   return self;
 }

 - (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
   self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
   if (self) {
     [self commonInit];
   }
   return self;
 }

 -(void)commonInit {
   // Already been setup through encoding/decoding
   if (self.tabBar) {
     return;
   }
   MDCTabBar *tabBar = [[MDCTabBar alloc] initWithFrame:CGRectZero];
   tabBar.alignment = MDCTabBarAlignmentJustified;
   tabBar.delegate = self;
   self.tabBar = tabBar;
   _tabBarShadow = [[MDCTabBarShadowView alloc] initWithFrame:CGRectZero];
 }

 - (void)encodeWithCoder:(NSCoder *)coder {
   [super encodeWithCoder:coder];
   [coder encodeObject:_viewControllers forKey:MDCTabBarViewControllerViewControllersKey];
   [coder encodeConditionalObject:_selectedViewController
                           forKey:MDCTabBarViewControllerSelectedViewControllerKey];
   [coder encodeObject:_tabBar forKey:MDCTabBarViewControllerTabBarKey];
   [coder encodeConditionalObject:_delegate forKey:MDCTabBarViewControllerDelegateKey];
 }

 - (void)viewDidLoad {
   [super viewDidLoad];
   UIView *view = self.view;
   view.clipsToBounds = YES;
   view.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleWidth |
                           UIViewAutoresizingFlexibleRightMargin |
                           UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleHeight |
                           UIViewAutoresizingFlexibleBottomMargin;
   [view addSubview:_tabBarShadow];
   [view addSubview:self.tabBar];
   [self updateOldViewControllers:nil to:_viewControllers];
   [self updateOldSelectedViewController:nil to:_selectedViewController];
 }

 - (void)viewDidLayoutSubviews {
   [super viewDidLayoutSubviews];
   [self updateLayout];
 }

 #pragma mark - Properties

 - (BOOL)tabBarHidden {
   return self.tabBar.hidden;
 }

 - (void)setTabBarHidden:(BOOL)hidden {
   [self setTabBarHidden:hidden animated:NO];
 }

 - (void)setTabBarHidden:(BOOL)hidden animated:(BOOL)animated {
   if (_tabBar.hidden != hidden) {
     if (animated) {
       // Before entering our animation block put the view's layout in a good state.
       [self.view layoutIfNeeded];
     }
     _tabBarWantsToBeHidden = hidden;
     // Hiding the tab bar has the side effect of growing the current viewController to use that
     // space. This does that in its layoutSubViews.
     [self.view setNeedsLayout];
     if (animated) {
       if (!hidden) {
         // If we are showing, set the state before the animation.
         _tabBar.hidden = hidden;
         _tabBarShadow.hidden = hidden;
       }
       [UIView animateWithDuration:MDCTabBarViewControllerAnimationDuration
           animations:^{
             [self.view layoutIfNeeded];
           }
           completion:^(__unused BOOL finished) {
             // If we are hiding, set the state after the animation.
             self.tabBar.hidden = hidden;
             self->_tabBarShadow.hidden = hidden;
           }];
     } else {
       _tabBar.hidden = hidden;
       _tabBarShadow.hidden = hidden;
     }
   }
 }

 - (void)setViewControllers:(NSArray<UIViewController *> *)viewControllers {
   NSArray<UIViewController *> *oldViewControllers = _viewControllers;
   _viewControllers = [viewControllers copy];
   [self updateOldViewControllers:oldViewControllers to:viewControllers];
 }

 - (void)updateOldViewControllers:(NSArray<UIViewController *> *)oldViewControllers
                               to:(NSArray<UIViewController *> *)viewControllers {
   if (!self.isViewLoaded || [oldViewControllers isEqual:viewControllers]) {
     return;
   }

   if (![oldViewControllers isEqual:viewControllers]) {
     // For all view controllers that this is removing, follow UIViewController.h's rules for
     // for removing a child view controller. See the comments in UIViewController.h for more
     // information.
     for (UIViewController *viewController in oldViewControllers) {
       if (![viewControllers containsObject:viewController]) {
         [viewController willMoveToParentViewController:nil];
         if (viewController.isViewLoaded) {
           [viewController.view removeFromSuperview];
         }
         [viewController removeFromParentViewController];
       }
     }
     // Show the newly-visible view controller.
     [self updateTabBarItems];
   }
 }

 - (void)updateOldSelectedViewController:(nullable UIViewController *)oldSelectedViewController
                                      to:(nullable UIViewController *)selectedViewController {
   if (!self.isViewLoaded || oldSelectedViewController == selectedViewController) {
     return;
   }
   if (selectedViewController) {
     NSAssert([_viewControllers containsObject:selectedViewController], @"not one of us.");
   }

   if (![self.childViewControllers containsObject:selectedViewController]) {
     [self addChildViewController:selectedViewController];
     UIView *view = selectedViewController.view;
     [self.view addSubview:view];
     [selectedViewController didMoveToParentViewController:self];
   }
   [self updateTabBarItems];
   BOOL animated = NO;
   [oldSelectedViewController beginAppearanceTransition:NO animated:animated];
   [selectedViewController beginAppearanceTransition:YES animated:animated];

   [self transitionViewsWithoutAnimationFromViewController:oldSelectedViewController
                                          toViewController:selectedViewController];

   [oldSelectedViewController endAppearanceTransition];
   [selectedViewController endAppearanceTransition];

   if (selectedViewController) {
     self.tabBar.selectedItem = selectedViewController.tabBarItem;
   }
   [self setNeedsStatusBarAppearanceUpdate];
 }

 - (void)setSelectedViewController:(nullable UIViewController *)selectedViewController {
   UIViewController *oldSelectedViewController = _selectedViewController;
   _selectedViewController = selectedViewController;
   [self updateOldSelectedViewController:oldSelectedViewController to:selectedViewController];
 }

 #pragma mark - private

 // Encapsulate the actual view handling.
 - (void)transitionViewsWithoutAnimationFromViewController:(UIViewController *)from
                                          toViewController:(UIViewController *)to {
   [self.view setNeedsLayout];
   [self.view layoutIfNeeded];
   from.view.hidden = YES;
   to.view.hidden = NO;
 }

 // Either this has just come into existence or its array of viewControllers has changed.
 // Update the TabBar from the array of viewControllers.
 - (void)updateTabBarItems {
   NSMutableArray<UITabBarItem *> *items = [NSMutableArray array];
   BOOL hasTitles = NO;
   BOOL hasImages = NO;
   for (UIViewController *child in _viewControllers) {
     UITabBarItem *tabBarItem = child.tabBarItem;
     [items addObject:tabBarItem];
     if (tabBarItem.title.length) {
       hasTitles = YES;
     }
     if (tabBarItem.image) {
       hasImages = YES;
     }
   }
   // This class preserves the invariant that if the selected controller is not nil, it is contained
   // in the array of viewControllers.
   if (![_viewControllers containsObject:_selectedViewController]) {
     self.selectedViewController = nil;
   }
   self.tabBar.items = items;
   // The default height of the tab bar depends on the underlying UITabBarItems of
   // the viewControllers.
   if (hasImages && hasTitles) {
     self.tabBar.itemAppearance = MDCTabBarItemAppearanceTitledImages;
   } else if (hasImages) {
     self.tabBar.itemAppearance = MDCTabBarItemAppearanceImages;
   } else {
     self.tabBar.itemAppearance = MDCTabBarItemAppearanceTitles;
   }
   [self.view bringSubviewToFront:_tabBarShadow];
   [self.view bringSubviewToFront:self.tabBar];
 }

 - (nullable UIViewController *)controllerWithView:(nullable UIView *)view {
   for (UIViewController *child in _viewControllers) {
     if (child.view == view) {
       return child;
     }
   }
   return nil;
 }

 - (void)updateLayout {
   CGRect bounds = self.view.bounds;
   CGFloat tabBarHeight = [[_tabBar class] defaultHeightForBarPosition:UIBarPositionBottom
                                                        itemAppearance:_tabBar.itemAppearance];
 #if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
   if (@available(iOS 11.0, *)) {
     tabBarHeight += self.view.safeAreaInsets.bottom;
   }
 #endif

   CGRect currentViewFrame = bounds;
   CGRect tabBarFrame = CGRectMake(bounds.origin.x, bounds.origin.y + bounds.size.height,
                                   bounds.size.width, tabBarHeight);
   if (!_tabBarWantsToBeHidden) {
     CGRectDivide(bounds, &tabBarFrame, &currentViewFrame, tabBarHeight, CGRectMaxYEdge);
   }
   _tabBar.frame = tabBarFrame;
   _tabBarShadow.frame = tabBarFrame;
   _selectedViewController.view.frame = currentViewFrame;
 }

 #pragma mark -  MDCTabBarDelegate

 - (BOOL)tabBar:(UITabBar *)tabBar shouldSelectItem:(UITabBarItem *)item {
   if ([_delegate respondsToSelector:@selector(tabBarController:shouldSelectViewController:)]) {
     NSUInteger index = [tabBar.items indexOfObject:item];
     if (index < _viewControllers.count) {
       UIViewController *newSelected = _viewControllers[index];
       return [_delegate tabBarController:self shouldSelectViewController:newSelected];
     }
   }
   return YES;
 }

 - (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item {
   NSUInteger index = [tabBar.items indexOfObject:item];
   if (index < _viewControllers.count) {
     UIViewController *newSelected = _viewControllers[index];
     if (newSelected != self.selectedViewController) {
       self.selectedViewController = newSelected;
     }
     if ([_delegate respondsToSelector:@selector(tabBarController:didSelectViewController:)]) {
       [_delegate tabBarController:self didSelectViewController:newSelected];
     }
   }
 }

 - (UIBarPosition)positionForBar:(id <UIBarPositioning>)bar {
   if (_tabBar == bar) {
     return UIBarPositionBottom;
   } else {
     return UIBarPositionAny;
   }
 }

 #pragma mark - UIViewController status bar

 - (nullable UIViewController *)childViewControllerForStatusBarStyle {
   return _selectedViewController;
 }

 - (nullable UIViewController *)childViewControllerForStatusBarHidden {
   return _selectedViewController;
 }

 @end
	/*
	Copyright 2017-present the Material Components for iOS authors. All Rights Reserved.

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	*/

	#import "MDCTabBarViewController.h"

	#import "MaterialShadowElevations.h"
	#import "MaterialShadowLayer.h"

	static NSString *const MDCTabBarViewControllerViewControllersKey =
	@"MDCTabBarViewControllerViewControllersKey";
	static NSString *const MDCTabBarViewControllerSelectedViewControllerKey =
	@"MDCTabBarViewControllerSelectedViewControllerKey";
	static NSString *const MDCTabBarViewControllerDelegateKey = @"MDCTabBarViewControllerDelegateKey";
	static NSString *const MDCTabBarViewControllerTabBarKey = @"MDCTabBarViewControllerTabBarKey";

	const CGFloat MDCTabBarViewControllerAnimationDuration = 0.3f;

	/**
	* View to host shadow for the tab bar.
	*/
	@interface MDCTabBarShadowView : UIView
	@end

	@implementation MDCTabBarShadowView

	+ (Class)layerClass {
	return [MDCShadowLayer class];
	}

	- (instancetype)initWithFrame:(CGRect)frame {
	self = [super initWithFrame:frame];
	if (self) {
	[self commonMDCTabBarShadowViewInitialization];
	}
	return self;
	}

	- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
	self = [super initWithCoder:aDecoder];
	if (self) {
	[self commonMDCTabBarShadowViewInitialization];
	}
	return self;
	}

	- (void)commonMDCTabBarShadowViewInitialization {
	MDCShadowLayer shadowLayer = (MDCShadowLayer )self.layer;
	[shadowLayer setElevation:MDCShadowElevationMenu];
	}

	@end

	@interface MDCTabBarViewController ()

	@property(nonatomic, readwrite, nonnull) MDCTabBar *tabBar;

	@end

	@implementation MDCTabBarViewController {
	/** For showing/hiding, Animation needs to know where it wants to end up. */
	BOOL _tabBarWantsToBeHidden;
	MDCTabBarShadowView *_tabBarShadow;
	}

	- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder {
	self = [super initWithCoder:aDecoder];
	if (self) {
	_viewControllers = [aDecoder decodeObjectOfClass:[NSArray class]
	forKey:MDCTabBarViewControllerViewControllersKey];
	self.selectedViewController =
	[aDecoder decodeObjectOfClass:[UIViewController class]
	forKey:MDCTabBarViewControllerSelectedViewControllerKey];
	_tabBar = [aDecoder decodeObjectOfClass:[MDCTabBar class]
	forKey:MDCTabBarViewControllerTabBarKey];
	_delegate = [aDecoder decodeObjectForKey:MDCTabBarViewControllerDelegateKey];
	[self commonInit];
	}
	return self;
	}

	- (instancetype)init {
	self = [super init];
	if (self) {
	[self commonInit];
	}
	return self;
	}

	- (instancetype)initWithNibName:(NSString )nibNameOrNil bundle:(NSBundle )nibBundleOrNil {
	self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
	if (self) {
	[self commonInit];
	}
	return self;
	}

	-(void)commonInit {
	// Already been setup through encoding/decoding
	if (self.tabBar) {
	return;
	}
	MDCTabBar *tabBar = [[MDCTabBar alloc] initWithFrame:CGRectZero];
	tabBar.alignment = MDCTabBarAlignmentJustified;
	tabBar.delegate = self;
	self.tabBar = tabBar;
	_tabBarShadow = [[MDCTabBarShadowView alloc] initWithFrame:CGRectZero];
	}

	- (void)encodeWithCoder:(NSCoder *)coder {
	[super encodeWithCoder:coder];
	[coder encodeObject:_viewControllers forKey:MDCTabBarViewControllerViewControllersKey];
	[coder encodeConditionalObject:_selectedViewController
	forKey:MDCTabBarViewControllerSelectedViewControllerKey];
	[coder encodeObject:_tabBar forKey:MDCTabBarViewControllerTabBarKey];
	[coder encodeConditionalObject:_delegate forKey:MDCTabBarViewControllerDelegateKey];
	}

	- (void)viewDidLoad {
	[super viewDidLoad];
	UIView *view = self.view;
	view.clipsToBounds = YES;
	view.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin \| UIViewAutoresizingFlexibleWidth \|
	UIViewAutoresizingFlexibleRightMargin \|
	UIViewAutoresizingFlexibleTopMargin \| UIViewAutoresizingFlexibleHeight \|
	UIViewAutoresizingFlexibleBottomMargin;
	[view addSubview:_tabBarShadow];
	[view addSubview:self.tabBar];
	[self updateOldViewControllers:nil to:_viewControllers];
	[self updateOldSelectedViewController:nil to:_selectedViewController];
	}

	- (void)viewDidLayoutSubviews {
	[super viewDidLayoutSubviews];
	[self updateLayout];
	}

	#pragma mark - Properties

	- (BOOL)tabBarHidden {
	return self.tabBar.hidden;
	}

	- (void)setTabBarHidden:(BOOL)hidden {
	[self setTabBarHidden:hidden animated:NO];
	}

	- (void)setTabBarHidden:(BOOL)hidden animated:(BOOL)animated {
	if (_tabBar.hidden != hidden) {
	if (animated) {
	// Before entering our animation block put the view's layout in a good state.
	[self.view layoutIfNeeded];
	}
	_tabBarWantsToBeHidden = hidden;
	// Hiding the tab bar has the side effect of growing the current viewController to use that
	// space. This does that in its layoutSubViews.
	[self.view setNeedsLayout];
	if (animated) {
	if (!hidden) {
	// If we are showing, set the state before the animation.
	_tabBar.hidden = hidden;
	_tabBarShadow.hidden = hidden;
	}
	[UIView animateWithDuration:MDCTabBarViewControllerAnimationDuration
	animations:^{
	[self.view layoutIfNeeded];
	}
	completion:^(__unused BOOL finished) {
	// If we are hiding, set the state after the animation.
	self.tabBar.hidden = hidden;
	self->_tabBarShadow.hidden = hidden;
	}];
	} else {
	_tabBar.hidden = hidden;
	_tabBarShadow.hidden = hidden;
	}
	}
	}

	- (void)setViewControllers:(NSArray<UIViewController > )viewControllers {
	NSArray<UIViewController > oldViewControllers = _viewControllers;
	_viewControllers = [viewControllers copy];
	[self updateOldViewControllers:oldViewControllers to:viewControllers];
	}

	- (void)updateOldViewControllers:(NSArray<UIViewController > )oldViewControllers
	to:(NSArray<UIViewController > )viewControllers {
	if (!self.isViewLoaded \|\| [oldViewControllers isEqual:viewControllers]) {
	return;
	}

	if (![oldViewControllers isEqual:viewControllers]) {
	// For all view controllers that this is removing, follow UIViewController.h's rules for
	// for removing a child view controller. See the comments in UIViewController.h for more
	// information.
	for (UIViewController *viewController in oldViewControllers) {
	if (![viewControllers containsObject:viewController]) {
	[viewController willMoveToParentViewController:nil];
	if (viewController.isViewLoaded) {
	[viewController.view removeFromSuperview];
	}
	[viewController removeFromParentViewController];
	}
	}
	// Show the newly-visible view controller.
	[self updateTabBarItems];
	}
	}

	- (void)updateOldSelectedViewController:(nullable UIViewController *)oldSelectedViewController
	to:(nullable UIViewController *)selectedViewController {
	if (!self.isViewLoaded \|\| oldSelectedViewController == selectedViewController) {
	return;
	}
	if (selectedViewController) {
	NSAssert([_viewControllers containsObject:selectedViewController], @"not one of us.");
	}

	if (![self.childViewControllers containsObject:selectedViewController]) {
	[self addChildViewController:selectedViewController];
	UIView *view = selectedViewController.view;
	[self.view addSubview:view];
	[selectedViewController didMoveToParentViewController:self];
	}
	[self updateTabBarItems];
	BOOL animated = NO;
	[oldSelectedViewController beginAppearanceTransition:NO animated:animated];
	[selectedViewController beginAppearanceTransition:YES animated:animated];

	[self transitionViewsWithoutAnimationFromViewController:oldSelectedViewController
	toViewController:selectedViewController];

	[oldSelectedViewController endAppearanceTransition];
	[selectedViewController endAppearanceTransition];

	if (selectedViewController) {
	self.tabBar.selectedItem = selectedViewController.tabBarItem;
	}
	[self setNeedsStatusBarAppearanceUpdate];
	}

	- (void)setSelectedViewController:(nullable UIViewController *)selectedViewController {
	UIViewController *oldSelectedViewController = _selectedViewController;
	_selectedViewController = selectedViewController;
	[self updateOldSelectedViewController:oldSelectedViewController to:selectedViewController];
	}

	#pragma mark - private

	// Encapsulate the actual view handling.
	- (void)transitionViewsWithoutAnimationFromViewController:(UIViewController *)from
	toViewController:(UIViewController *)to {
	[self.view setNeedsLayout];
	[self.view layoutIfNeeded];
	from.view.hidden = YES;
	to.view.hidden = NO;
	}

	// Either this has just come into existence or its array of viewControllers has changed.
	// Update the TabBar from the array of viewControllers.
	- (void)updateTabBarItems {
	NSMutableArray<UITabBarItem > items = [NSMutableArray array];
	BOOL hasTitles = NO;
	BOOL hasImages = NO;
	for (UIViewController *child in _viewControllers) {
	UITabBarItem *tabBarItem = child.tabBarItem;
	[items addObject:tabBarItem];
	if (tabBarItem.title.length) {
	hasTitles = YES;
	}
	if (tabBarItem.image) {
	hasImages = YES;
	}
	}
	// This class preserves the invariant that if the selected controller is not nil, it is contained
	// in the array of viewControllers.
	if (![_viewControllers containsObject:_selectedViewController]) {
	self.selectedViewController = nil;
	}
	self.tabBar.items = items;
	// The default height of the tab bar depends on the underlying UITabBarItems of
	// the viewControllers.
	if (hasImages && hasTitles) {
	self.tabBar.itemAppearance = MDCTabBarItemAppearanceTitledImages;
	} else if (hasImages) {
	self.tabBar.itemAppearance = MDCTabBarItemAppearanceImages;
	} else {
	self.tabBar.itemAppearance = MDCTabBarItemAppearanceTitles;
	}
	[self.view bringSubviewToFront:_tabBarShadow];
	[self.view bringSubviewToFront:self.tabBar];
	}

	- (nullable UIViewController )controllerWithView:(nullable UIView )view {
	for (UIViewController *child in _viewControllers) {
	if (child.view == view) {
	return child;
	}
	}
	return nil;
	}

	- (void)updateLayout {
	CGRect bounds = self.view.bounds;
	CGFloat tabBarHeight = [[_tabBar class] defaultHeightForBarPosition:UIBarPositionBottom
	itemAppearance:_tabBar.itemAppearance];
	#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
	if (@available(iOS 11.0, *)) {
	tabBarHeight += self.view.safeAreaInsets.bottom;
	}
	#endif

	CGRect currentViewFrame = bounds;
	CGRect tabBarFrame = CGRectMake(bounds.origin.x, bounds.origin.y + bounds.size.height,
	bounds.size.width, tabBarHeight);
	if (!_tabBarWantsToBeHidden) {
	CGRectDivide(bounds, &tabBarFrame, &currentViewFrame, tabBarHeight, CGRectMaxYEdge);
	}
	_tabBar.frame = tabBarFrame;
	_tabBarShadow.frame = tabBarFrame;
	_selectedViewController.view.frame = currentViewFrame;
	}

	#pragma mark - MDCTabBarDelegate

	- (BOOL)tabBar:(UITabBar )tabBar shouldSelectItem:(UITabBarItem )item {
	if ([_delegate respondsToSelector:@selector(tabBarController:shouldSelectViewController:)]) {
	NSUInteger index = [tabBar.items indexOfObject:item];
	if (index < _viewControllers.count) {
	UIViewController *newSelected = _viewControllers[index];
	return [_delegate tabBarController:self shouldSelectViewController:newSelected];
	}
	}
	return YES;
	}

	- (void)tabBar:(UITabBar )tabBar didSelectItem:(UITabBarItem )item {
	NSUInteger index = [tabBar.items indexOfObject:item];
	if (index < _viewControllers.count) {
	UIViewController *newSelected = _viewControllers[index];
	if (newSelected != self.selectedViewController) {
	self.selectedViewController = newSelected;
	}
	if ([_delegate respondsToSelector:@selector(tabBarController:didSelectViewController:)]) {
	[_delegate tabBarController:self didSelectViewController:newSelected];
	}
	}
	}

	- (UIBarPosition)positionForBar:(id <UIBarPositioning>)bar {
	if (_tabBar == bar) {
	return UIBarPositionBottom;
	} else {
	return UIBarPositionAny;
	}
	}

	#pragma mark - UIViewController status bar

	- (nullable UIViewController *)childViewControllerForStatusBarStyle {
	return _selectedViewController;
	}

	- (nullable UIViewController *)childViewControllerForStatusBarHidden {
	return _selectedViewController;
	}

	@end