components/ButtonBar/src/private/MDCAppBarButtonBarBuilder.m - external/github.com/material-components/material-components-ios - Git at Google

 /*
  Copyright 2016-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 "MDCAppBarButtonBarBuilder.h"

 #import <objc/runtime.h>
 #import <MDFInternationalization/MDFInternationalization.h>

 #import "MaterialButtons.h"
 #import "MDCButtonBarButton.h"
 #import "MDCButtonBar+Private.h"

 // Additional insets for the left-most or right-most items.
 static const CGFloat kEdgeButtonAdditionalMarginPhone = 4.f;
 static const CGFloat kEdgeButtonAdditionalMarginPad = 12.f;

 // The default MDCButton's alpha for display state is 0.1f which in the context of bar buttons
 // makes it practically invisible. Setting button to a higher opacity is closer to what the
 // button should look like when it is disabled.
 static const CGFloat kDisabledButtonAlpha = 0.38f;

 // Default content inset for buttons.
 static const UIEdgeInsets kButtonInset = {0, 12.0f, 0, 12.0f};

 // Indiana Jones style placeholder view for UINavigationBar. Ownership of UIBarButtonItem.customView
 // and UINavigationItem.titleView are normally transferred to UINavigationController but we plan to
 // steal them away. In order to avoid crashing during KVO updates, we steal the view away and
 // replace it with a sandbag view.
 @interface MDCButtonBarSandbagView : UIView
 @end

 @interface UIBarButtonItem (MDCHeaderInternal)

 // Internal version of the standard -customView property. When an item is pushed onto a
 // UINavigationController stack, any -customView object is moved over to this property. This
 // prevents UINavigationController from adding the customView to its own view hierarchy.
 @property(nonatomic, strong, setter=mdc_setCustomView:) UIView *mdc_customView;

 @end

 @implementation MDCAppBarButtonBarBuilder {
   NSMutableDictionary<NSNumber *, UIFont *> *_fonts;
   NSMutableDictionary<NSNumber *, UIColor *> *_titleColors;
 }

 - (instancetype)init {
   self = [super init];
   if (self) {
     _fonts = [NSMutableDictionary dictionary];
     _titleColors = [NSMutableDictionary dictionary];
   }
   return self;
 }

 - (nullable UIFont *)titleFontForState:(UIControlState)state {
   UIFont *font = _fonts[@(state)];
   if (!font && state != UIControlStateNormal) {
     font = _fonts[@(UIControlStateNormal)];
   }
   return font;
 }

 - (void)setTitleFont:(UIFont *)font forState:(UIControlState)state {
   _fonts[@(state)] = font;
 }

 - (UIColor *)titleColorForState:(UIControlState)state {
   UIColor *color = _titleColors[@(state)];
   if (!color && state != UIControlStateNormal) {
     color = _titleColors[@(UIControlStateNormal)];
   }
   return color;
 }

 - (void)setTitleColor:(UIColor *)color forState:(UIControlState)state {
   _titleColors[@(state)] = color;
 }

 #pragma mark - MDCBarButtonItemBuilding

 - (UIView *)buttonBar:(MDCButtonBar *)buttonBar
           viewForItem:(UIBarButtonItem *)buttonItem
           layoutHints:(MDCBarButtonItemLayoutHints)layoutHints {
   if (buttonItem == nil) {
     return nil;
   }

   // Transfer custom view ownership if necessary.
   [self transferCustomViewOwnershipForBarButtonItem:buttonItem];

   // Take the real custom view if it exists instead of sandbag view.
   UIView *customView =
       buttonItem.mdc_customView ? buttonItem.mdc_customView : buttonItem.customView;
   if (customView) {
     return customView;
   }

 // NOTE: This assertion does not occur in release builds because it is accessing a private api.
 #if DEBUG
   NSAssert(![[buttonItem valueForKey:@"isSystemItem"] boolValue],
            @"Instances of %@ must not be initialized with %@ when working with %@."
            @" This is because we cannot extract the system item type from the item.",
            NSStringFromClass([buttonItem class]),
            NSStringFromSelector(@selector(initWithBarButtonSystemItem:target:action:)),
            NSStringFromClass([MDCButtonBar class]));
 #endif

   MDCButtonBarButton *button = [[MDCButtonBarButton alloc] init];
   [button setBackgroundColor:[UIColor clearColor] forState:UIControlStateNormal];
   button.disabledAlpha = kDisabledButtonAlpha;
   if (buttonBar.inkColor) {
     button.inkColor = buttonBar.inkColor;
   }

   button.exclusiveTouch = YES;

   [MDCAppBarButtonBarBuilder configureButton:button fromButtonItem:buttonItem];

   [button setTitleColor:self.buttonTitleColor forState:UIControlStateNormal];
   [button setUnderlyingColorHint:self.buttonUnderlyingColor];
   for (NSNumber *state in _fonts) {
     UIFont *font = _fonts[state];
     [button setTitleFont:font forState:(UIControlState)state.intValue];
   }
   for (NSNumber *state in _titleColors) {
     UIColor *color = _titleColors[state];
     [button setTitleColor:color forState:(UIControlState)state.intValue];
   }

   [self updateButton:button withItem:buttonItem barMetrics:UIBarMetricsDefault];

   // Contrary to intuition, UIKit provides the UIBarButtonItem as the action's first argument when
   // bar buttons are tapped, NOT the button itself. Simply adding the item's target/action to the
   // button does not allow us to pass the expected argument to the target.
   //
   // MDCButtonBar provides didTapButton:event: to which we can pass button events
   // so that the correct argument is ultimately passed along.
   [button addTarget:buttonBar
                 action:@selector(didTapButton:event:)
       forControlEvents:UIControlEventTouchUpInside];

   UIEdgeInsets contentInsets = [MDCAppBarButtonBarBuilder
       contentInsetsForButton:button
               layoutPosition:buttonBar.layoutPosition
                  layoutHints:layoutHints
              layoutDirection:[buttonBar mdf_effectiveUserInterfaceLayoutDirection]
                                 userInterfaceIdiom:[self usePadInsetsForButtonBar:buttonBar] ?
                                 UIUserInterfaceIdiomPad : UIUserInterfaceIdiomPhone];

   button.contentEdgeInsets = contentInsets;
   button.enabled = buttonItem.enabled;
   button.accessibilityLabel = buttonItem.accessibilityLabel;
   button.accessibilityHint = buttonItem.accessibilityHint;
   button.accessibilityValue = buttonItem.accessibilityValue;
   button.accessibilityIdentifier = buttonItem.accessibilityIdentifier;

   return button;
 }

 #pragma mark - Private

 // Used to determine whether or not to apply insets relevant for iPad or use smaller iPhone size
 // Because only widths are affected, we use horizontal size class
 - (BOOL)usePadInsetsForButtonBar:(MDCButtonBar *)buttonBar {
   const BOOL isPad = [[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad;
   if (isPad && buttonBar.traitCollection.horizontalSizeClass == UIUserInterfaceSizeClassRegular) {
     return YES;
   }
   return NO;
 }

 + (UIEdgeInsets)contentInsetsForButton:(MDCButton *)button
                         layoutPosition:(MDCButtonBarLayoutPosition)layoutPosition
                            layoutHints:(MDCBarButtonItemLayoutHints)layoutHints
                        layoutDirection:(UIUserInterfaceLayoutDirection)layoutDirection
                     userInterfaceIdiom:(UIUserInterfaceIdiom)userInterfaceIdiom {
   UIEdgeInsets contentInsets = kButtonInset;
   if ([button currentImage] || [button currentTitle].length) {
     BOOL isPad = userInterfaceIdiom == UIUserInterfaceIdiomPad;
     CGFloat additionalInset =
         (isPad ? kEdgeButtonAdditionalMarginPad : kEdgeButtonAdditionalMarginPhone);
     BOOL isFirstButton = (layoutHints & MDCBarButtonItemLayoutHintsIsFirstButton) ==
                              MDCBarButtonItemLayoutHintsIsFirstButton;
     BOOL isLastButton = (layoutHints & MDCBarButtonItemLayoutHintsIsLastButton) ==
                             MDCBarButtonItemLayoutHintsIsLastButton;
     if (isFirstButton && layoutPosition == MDCButtonBarLayoutPositionLeading) {
       // Left-most button in LTR, and right-most button in RTL.
       if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
         contentInsets.left += additionalInset;
       } else {
         contentInsets.right += additionalInset;
       }
     } else if (isFirstButton && layoutPosition == MDCButtonBarLayoutPositionTrailing) {
       // Right-most button in LTR, and left-most button in RTL.
       if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
         contentInsets.right += additionalInset;
       } else {
         contentInsets.left += additionalInset;
       }
     }
     if (isLastButton && layoutPosition == MDCButtonBarLayoutPositionTrailing) {
       // Left-most button in LTR, and right-most button in RTL.
       if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
         contentInsets.left += additionalInset;
       } else {
         contentInsets.right += additionalInset;
       }
     } else if (isLastButton && layoutPosition == MDCButtonBarLayoutPositionLeading) {
       // Right-most button in LTR, and left-most button in RTL.
       if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
         contentInsets.right += additionalInset;
       } else {
         contentInsets.left += additionalInset;
       }
     }
   } else {
     NSAssert(0, @"No button title or image");
   }

   return contentInsets;
 }

 + (void)configureButton:(MDCButton *)destinationButton
          fromButtonItem:(UIBarButtonItem *)sourceButtonItem {
   if (sourceButtonItem == nil || destinationButton == nil) {
     return;
   }

   if (sourceButtonItem.title != nil) {
     [destinationButton setTitle:sourceButtonItem.title forState:UIControlStateNormal];
   }
   if (sourceButtonItem.image != nil) {
     [destinationButton setImage:sourceButtonItem.image forState:UIControlStateNormal];
   }
   if (sourceButtonItem.tintColor != nil) {
     destinationButton.tintColor = sourceButtonItem.tintColor;
   }

   if (sourceButtonItem.title) {
     destinationButton.inkStyle = MDCInkStyleBounded;
   } else {
     destinationButton.inkStyle = MDCInkStyleUnbounded;
   }

   destinationButton.tag = sourceButtonItem.tag;
 }

 - (void)updateButton:(UIButton *)button
             withItem:(UIBarButtonItem *)item
           barMetrics:(UIBarMetrics)barMetrics {
   [self updateButton:button withItem:item forState:UIControlStateNormal barMetrics:barMetrics];
   [self updateButton:button withItem:item forState:UIControlStateHighlighted barMetrics:barMetrics];
   [self updateButton:button withItem:item forState:UIControlStateDisabled barMetrics:barMetrics];
 }

 - (void)updateButton:(UIButton *)button
             withItem:(UIBarButtonItem *)item
             forState:(UIControlState)state
           barMetrics:(UIBarMetrics)barMetrics {
   NSString *title = item.title ? item.title : @"";
   if ([UIButton instancesRespondToSelector:@selector(setAttributedTitle:forState:)]) {
     NSMutableDictionary<NSString *, id> *attributes = [NSMutableDictionary dictionary];

     // UIBarButtonItem's appearance proxy values don't appear to come "for free" like they do with
     // typical UIView instances, so we're attempting to recreate the behavior here.
     NSArray *appearanceProxies = @[ [item.class appearance] ];
     for (UIBarButtonItem *appearance in appearanceProxies) {
       [attributes addEntriesFromDictionary:[appearance titleTextAttributesForState:state]];
     }
     [attributes addEntriesFromDictionary:[item titleTextAttributesForState:state]];
     if ([attributes count] > 0) {
       [button
           setAttributedTitle:[[NSAttributedString alloc] initWithString:title attributes:attributes]
                     forState:state];
     }
   } else {
     [button setTitle:title forState:state];
   }

   UIImage *backgroundImage = [item backgroundImageForState:state barMetrics:barMetrics];
   if (backgroundImage) {
     [button setBackgroundImage:backgroundImage forState:state];
   }
 }

 - (void)transferCustomViewOwnershipForBarButtonItem:(UIBarButtonItem *)barButtonItem {
   UIView *customView = barButtonItem.customView;
   if (customView && ![customView isKindOfClass:[MDCButtonBarSandbagView class]]) {
     // Transfer ownership of any UIBarButtonItem.customView to the internal property
     // so that UINavigationController won't steal the view from us.
     barButtonItem.mdc_customView = customView;
     barButtonItem.customView = [[MDCButtonBarSandbagView alloc] init];
   }
 }

 @end

 @implementation MDCButtonBarSandbagView
 @end

 @implementation UIBarButtonItem (MDCHeaderInternal)

 @dynamic mdc_customView;

 - (UIView *)mdc_customView {
   return objc_getAssociatedObject(self, _cmd);
 }

 - (void)mdc_setCustomView:(UIView *)customView {
   objc_setAssociatedObject(self, @selector(mdc_customView), customView,
                            OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }

 @end
	/*
	Copyright 2016-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 "MDCAppBarButtonBarBuilder.h"

	#import <objc/runtime.h>
	#import <MDFInternationalization/MDFInternationalization.h>

	#import "MaterialButtons.h"
	#import "MDCButtonBarButton.h"
	#import "MDCButtonBar+Private.h"

	// Additional insets for the left-most or right-most items.
	static const CGFloat kEdgeButtonAdditionalMarginPhone = 4.f;
	static const CGFloat kEdgeButtonAdditionalMarginPad = 12.f;

	// The default MDCButton's alpha for display state is 0.1f which in the context of bar buttons
	// makes it practically invisible. Setting button to a higher opacity is closer to what the
	// button should look like when it is disabled.
	static const CGFloat kDisabledButtonAlpha = 0.38f;

	// Default content inset for buttons.
	static const UIEdgeInsets kButtonInset = {0, 12.0f, 0, 12.0f};

	// Indiana Jones style placeholder view for UINavigationBar. Ownership of UIBarButtonItem.customView
	// and UINavigationItem.titleView are normally transferred to UINavigationController but we plan to
	// steal them away. In order to avoid crashing during KVO updates, we steal the view away and
	// replace it with a sandbag view.
	@interface MDCButtonBarSandbagView : UIView
	@end

	@interface UIBarButtonItem (MDCHeaderInternal)

	// Internal version of the standard -customView property. When an item is pushed onto a
	// UINavigationController stack, any -customView object is moved over to this property. This
	// prevents UINavigationController from adding the customView to its own view hierarchy.
	@property(nonatomic, strong, setter=mdc_setCustomView:) UIView *mdc_customView;

	@end

	@implementation MDCAppBarButtonBarBuilder {
	NSMutableDictionary<NSNumber , UIFont > *_fonts;
	NSMutableDictionary<NSNumber , UIColor > *_titleColors;
	}

	- (instancetype)init {
	self = [super init];
	if (self) {
	_fonts = [NSMutableDictionary dictionary];
	_titleColors = [NSMutableDictionary dictionary];
	}
	return self;
	}

	- (nullable UIFont *)titleFontForState:(UIControlState)state {
	UIFont *font = _fonts[@(state)];
	if (!font && state != UIControlStateNormal) {
	font = _fonts[@(UIControlStateNormal)];
	}
	return font;
	}

	- (void)setTitleFont:(UIFont *)font forState:(UIControlState)state {
	_fonts[@(state)] = font;
	}

	- (UIColor *)titleColorForState:(UIControlState)state {
	UIColor *color = _titleColors[@(state)];
	if (!color && state != UIControlStateNormal) {
	color = _titleColors[@(UIControlStateNormal)];
	}
	return color;
	}

	- (void)setTitleColor:(UIColor *)color forState:(UIControlState)state {
	_titleColors[@(state)] = color;
	}

	#pragma mark - MDCBarButtonItemBuilding

	- (UIView )buttonBar:(MDCButtonBar )buttonBar
	viewForItem:(UIBarButtonItem *)buttonItem
	layoutHints:(MDCBarButtonItemLayoutHints)layoutHints {
	if (buttonItem == nil) {
	return nil;
	}

	// Transfer custom view ownership if necessary.
	[self transferCustomViewOwnershipForBarButtonItem:buttonItem];

	// Take the real custom view if it exists instead of sandbag view.
	UIView *customView =
	buttonItem.mdc_customView ? buttonItem.mdc_customView : buttonItem.customView;
	if (customView) {
	return customView;
	}

	// NOTE: This assertion does not occur in release builds because it is accessing a private api.
	#if DEBUG
	NSAssert(![[buttonItem valueForKey:@"isSystemItem"] boolValue],
	@"Instances of %@ must not be initialized with %@ when working with %@."
	@" This is because we cannot extract the system item type from the item.",
	NSStringFromClass([buttonItem class]),
	NSStringFromSelector(@selector(initWithBarButtonSystemItem:target:action:)),
	NSStringFromClass([MDCButtonBar class]));
	#endif

	MDCButtonBarButton *button = [[MDCButtonBarButton alloc] init];
	[button setBackgroundColor:[UIColor clearColor] forState:UIControlStateNormal];
	button.disabledAlpha = kDisabledButtonAlpha;
	if (buttonBar.inkColor) {
	button.inkColor = buttonBar.inkColor;
	}

	button.exclusiveTouch = YES;

	[MDCAppBarButtonBarBuilder configureButton:button fromButtonItem:buttonItem];

	[button setTitleColor:self.buttonTitleColor forState:UIControlStateNormal];
	[button setUnderlyingColorHint:self.buttonUnderlyingColor];
	for (NSNumber *state in _fonts) {
	UIFont *font = _fonts[state];
	[button setTitleFont:font forState:(UIControlState)state.intValue];
	}
	for (NSNumber *state in _titleColors) {
	UIColor *color = _titleColors[state];
	[button setTitleColor:color forState:(UIControlState)state.intValue];
	}

	[self updateButton:button withItem:buttonItem barMetrics:UIBarMetricsDefault];

	// Contrary to intuition, UIKit provides the UIBarButtonItem as the action's first argument when
	// bar buttons are tapped, NOT the button itself. Simply adding the item's target/action to the
	// button does not allow us to pass the expected argument to the target.
	//
	// MDCButtonBar provides didTapButton:event: to which we can pass button events
	// so that the correct argument is ultimately passed along.
	[button addTarget:buttonBar
	action:@selector(didTapButton:event:)
	forControlEvents:UIControlEventTouchUpInside];

	UIEdgeInsets contentInsets = [MDCAppBarButtonBarBuilder
	contentInsetsForButton:button
	layoutPosition:buttonBar.layoutPosition
	layoutHints:layoutHints
	layoutDirection:[buttonBar mdf_effectiveUserInterfaceLayoutDirection]
	userInterfaceIdiom:[self usePadInsetsForButtonBar:buttonBar] ?
	UIUserInterfaceIdiomPad : UIUserInterfaceIdiomPhone];

	button.contentEdgeInsets = contentInsets;
	button.enabled = buttonItem.enabled;
	button.accessibilityLabel = buttonItem.accessibilityLabel;
	button.accessibilityHint = buttonItem.accessibilityHint;
	button.accessibilityValue = buttonItem.accessibilityValue;
	button.accessibilityIdentifier = buttonItem.accessibilityIdentifier;

	return button;
	}

	#pragma mark - Private

	// Used to determine whether or not to apply insets relevant for iPad or use smaller iPhone size
	// Because only widths are affected, we use horizontal size class
	- (BOOL)usePadInsetsForButtonBar:(MDCButtonBar *)buttonBar {
	const BOOL isPad = [[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad;
	if (isPad && buttonBar.traitCollection.horizontalSizeClass == UIUserInterfaceSizeClassRegular) {
	return YES;
	}
	return NO;
	}

	+ (UIEdgeInsets)contentInsetsForButton:(MDCButton *)button
	layoutPosition:(MDCButtonBarLayoutPosition)layoutPosition
	layoutHints:(MDCBarButtonItemLayoutHints)layoutHints
	layoutDirection:(UIUserInterfaceLayoutDirection)layoutDirection
	userInterfaceIdiom:(UIUserInterfaceIdiom)userInterfaceIdiom {
	UIEdgeInsets contentInsets = kButtonInset;
	if ([button currentImage] \|\| [button currentTitle].length) {
	BOOL isPad = userInterfaceIdiom == UIUserInterfaceIdiomPad;
	CGFloat additionalInset =
	(isPad ? kEdgeButtonAdditionalMarginPad : kEdgeButtonAdditionalMarginPhone);
	BOOL isFirstButton = (layoutHints & MDCBarButtonItemLayoutHintsIsFirstButton) ==
	MDCBarButtonItemLayoutHintsIsFirstButton;
	BOOL isLastButton = (layoutHints & MDCBarButtonItemLayoutHintsIsLastButton) ==
	MDCBarButtonItemLayoutHintsIsLastButton;
	if (isFirstButton && layoutPosition == MDCButtonBarLayoutPositionLeading) {
	// Left-most button in LTR, and right-most button in RTL.
	if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
	contentInsets.left += additionalInset;
	} else {
	contentInsets.right += additionalInset;
	}
	} else if (isFirstButton && layoutPosition == MDCButtonBarLayoutPositionTrailing) {
	// Right-most button in LTR, and left-most button in RTL.
	if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
	contentInsets.right += additionalInset;
	} else {
	contentInsets.left += additionalInset;
	}
	}
	if (isLastButton && layoutPosition == MDCButtonBarLayoutPositionTrailing) {
	// Left-most button in LTR, and right-most button in RTL.
	if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
	contentInsets.left += additionalInset;
	} else {
	contentInsets.right += additionalInset;
	}
	} else if (isLastButton && layoutPosition == MDCButtonBarLayoutPositionLeading) {
	// Right-most button in LTR, and left-most button in RTL.
	if (layoutDirection == UIUserInterfaceLayoutDirectionLeftToRight) {
	contentInsets.right += additionalInset;
	} else {
	contentInsets.left += additionalInset;
	}
	}
	} else {
	NSAssert(0, @"No button title or image");
	}

	return contentInsets;
	}

	+ (void)configureButton:(MDCButton *)destinationButton
	fromButtonItem:(UIBarButtonItem *)sourceButtonItem {
	if (sourceButtonItem == nil \|\| destinationButton == nil) {
	return;
	}

	if (sourceButtonItem.title != nil) {
	[destinationButton setTitle:sourceButtonItem.title forState:UIControlStateNormal];
	}
	if (sourceButtonItem.image != nil) {
	[destinationButton setImage:sourceButtonItem.image forState:UIControlStateNormal];
	}
	if (sourceButtonItem.tintColor != nil) {
	destinationButton.tintColor = sourceButtonItem.tintColor;
	}

	if (sourceButtonItem.title) {
	destinationButton.inkStyle = MDCInkStyleBounded;
	} else {
	destinationButton.inkStyle = MDCInkStyleUnbounded;
	}

	destinationButton.tag = sourceButtonItem.tag;
	}

	- (void)updateButton:(UIButton *)button
	withItem:(UIBarButtonItem *)item
	barMetrics:(UIBarMetrics)barMetrics {
	[self updateButton:button withItem:item forState:UIControlStateNormal barMetrics:barMetrics];
	[self updateButton:button withItem:item forState:UIControlStateHighlighted barMetrics:barMetrics];
	[self updateButton:button withItem:item forState:UIControlStateDisabled barMetrics:barMetrics];
	}

	- (void)updateButton:(UIButton *)button
	withItem:(UIBarButtonItem *)item
	forState:(UIControlState)state
	barMetrics:(UIBarMetrics)barMetrics {
	NSString *title = item.title ? item.title : @"";
	if ([UIButton instancesRespondToSelector:@selector(setAttributedTitle:forState:)]) {
	NSMutableDictionary<NSString , id> attributes = [NSMutableDictionary dictionary];

	// UIBarButtonItem's appearance proxy values don't appear to come "for free" like they do with
	// typical UIView instances, so we're attempting to recreate the behavior here.
	NSArray *appearanceProxies = @[ [item.class appearance] ];
	for (UIBarButtonItem *appearance in appearanceProxies) {
	[attributes addEntriesFromDictionary:[appearance titleTextAttributesForState:state]];
	}
	[attributes addEntriesFromDictionary:[item titleTextAttributesForState:state]];
	if ([attributes count] > 0) {
	[button
	setAttributedTitle:[[NSAttributedString alloc] initWithString:title attributes:attributes]
	forState:state];
	}
	} else {
	[button setTitle:title forState:state];
	}

	UIImage *backgroundImage = [item backgroundImageForState:state barMetrics:barMetrics];
	if (backgroundImage) {
	[button setBackgroundImage:backgroundImage forState:state];
	}
	}

	- (void)transferCustomViewOwnershipForBarButtonItem:(UIBarButtonItem *)barButtonItem {
	UIView *customView = barButtonItem.customView;
	if (customView && ![customView isKindOfClass:[MDCButtonBarSandbagView class]]) {
	// Transfer ownership of any UIBarButtonItem.customView to the internal property
	// so that UINavigationController won't steal the view from us.
	barButtonItem.mdc_customView = customView;
	barButtonItem.customView = [[MDCButtonBarSandbagView alloc] init];
	}
	}

	@end

	@implementation MDCButtonBarSandbagView
	@end

	@implementation UIBarButtonItem (MDCHeaderInternal)

	@dynamic mdc_customView;

	- (UIView *)mdc_customView {
	return objc_getAssociatedObject(self, _cmd);
	}

	- (void)mdc_setCustomView:(UIView *)customView {
	objc_setAssociatedObject(self, @selector(mdc_customView), customView,
	OBJC_ASSOCIATION_RETAIN_NONATOMIC);
	}

	@end