iOS：UITableView、UIScrollView、UICollectionView内容为空时背景视图配置

UITableView、UIScrollView、UICollectionView数据为空通过协议方法设置 图片、提示文字、按钮（以及点击事件）

1、引入头文件

#import "UIScrollView+EmptyDataSet.h"

2、协议

DZNEmptyDataSetSource, DZNEmptyDataSetDelegate

3、协议方法

#pragma mark - DZNEmptyDataSetSource

#pragma mark - 设置顶部间距
- (CGFloat)verticalOffsetForEmptyDataSet:(UIScrollView *)scrollView{
    return 40;
}

#pragma mark - 解决：数据源、多个tableView切换时占位图片文字发生偏移问题
- (void)emptyDataSetWillAppear:(UIScrollView *)scrollView {
    [self.tableView setContentOffset:CGPointMake(0, self.tableView.contentInset.top)];
}

#pragma mark - empty 设置图片
-(UIImage *)imageForEmptyDataSet:(UIScrollView *)scrollView{
   return [UIImage imageNamed:@"图片"];        
}

#pragma mark - empty 设置提示label文字
-(NSAttributedString *)descriptionForEmptyDataSet:(UIScrollView *)scrollView{
    
    NSDictionary *dict = @{
        NSFontAttributeName:[UIFont systemFontOfSize:14],
        NSForegroundColorAttributeName:[UIColor blueColor]
    };
    
    NSString *des = @"暂无内容";
   
    if (des) {
        NSAttributedString *str = [[NSAttributedString alloc] initWithString:des attributes:dict];
        return str;
    }else{
        return nil;
    }
}

#pragma mark - empty 设置按钮背景图片
-(UIImage *)buttonBackgroundImageForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state{
     return [UIImage imageNamed:@"图片"]; 
}

#pragma mark - empty 设置按钮标题
-(NSAttributedString *)buttonTitleForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state{
    
    NSDictionary *dict = @{
        NSFontAttributeName:[UIFont systemFontOfSize:14],
        NSForegroundColorAttributeName:[UIColor blueColor]
    };
    
    NSString *des = @"点击刷新";
    if (des) {
        NSAttributedString *str = [[NSAttributedString alloc] initWithString:des attributes:dict];
        return str;
    }else{
        return nil;
    }
}

#pragma mark - empty 按钮点击事件
-(void)emptyDataSet:(UIScrollView *)scrollView didTapButton:(UIButton *)button{
    //按钮点击事件
}

#pragma mark - empty 点击背景事件
-(void)emptyDataSet:(UIScrollView *)scrollView didTapView:(UIView *)view{
    //点击背景事件

}

附件代码（引用代码）

UIScrollView+EmptyDataSet.h

#import <UIKit/UIKit.h>

@protocol DZNEmptyDataSetSource;
@protocol DZNEmptyDataSetDelegate;

#define DZNEmptyDataSetDeprecated(instead) DEPRECATED_MSG_ATTRIBUTE(" Use " # instead " instead")

/**
 A drop-in UITableView/UICollectionView superclass category for showing empty datasets whenever the view has no content to display.
 @discussion It will work automatically, by just conforming to DZNEmptyDataSetSource, and returning the data you want to show.
 */
@interface UIScrollView (EmptyDataSet)

/** The empty datasets data source. */
@property (nonatomic, weak) IBOutlet id <DZNEmptyDataSetSource> emptyDataSetSource;
/** The empty datasets delegate. */
@property (nonatomic, weak) IBOutlet id <DZNEmptyDataSetDelegate> emptyDataSetDelegate;
/** YES if any empty dataset is visible. */
@property (nonatomic, readonly, getter = isEmptyDataSetVisible) BOOL emptyDataSetVisible;

/**
 Reloads the empty dataset content receiver.
 @discussion Call this method to force all the data to refresh. Calling -reloadData is similar, but this forces only the empty dataset to reload, not the entire table view or collection view.
 */
- (void)reloadEmptyDataSet;

@end


/**
 The object that acts as the data source of the empty datasets.
 @discussion The data source must adopt the DZNEmptyDataSetSource protocol. The data source is not retained. All data source methods are optional.
 */
@protocol DZNEmptyDataSetSource <NSObject>
@optional

/**
 Asks the data source for the title of the dataset.
 The dataset uses a fixed font style by default, if no attributes are set. If you want a different font style, return a attributed string.
 
 @param scrollView A scrollView subclass informing the data source.
 @return An attributed string for the dataset title, combining font, text color, text pararaph style, etc.
 */
- (NSAttributedString *)titleForEmptyDataSet:(UIScrollView *)scrollView;

/**
 Asks the data source for the description of the dataset.
 The dataset uses a fixed font style by default, if no attributes are set. If you want a different font style, return a attributed string.
 
 @param scrollView A scrollView subclass informing the data source.
 @return An attributed string for the dataset description text, combining font, text color, text pararaph style, etc.
 */
- (NSAttributedString *)descriptionForEmptyDataSet:(UIScrollView *)scrollView;

/**
 Asks the data source for the image of the dataset.
 
 @param scrollView A scrollView subclass informing the data source.
 @return An image for the dataset.
 */
- (UIImage *)imageForEmptyDataSet:(UIScrollView *)scrollView;


/**
 Asks the data source for a tint color of the image dataset. Default is nil.
 
 @param scrollView A scrollView subclass object informing the data source.
 @return A color to tint the image of the dataset.
 */
- (UIColor *)imageTintColorForEmptyDataSet:(UIScrollView *)scrollView;

/**
 *  Asks the data source for the image animation of the dataset.
 *
 *  @param scrollView A scrollView subclass object informing the delegate.
 *
 *  @return image animation
 */
- (CAAnimation *) imageAnimationForEmptyDataSet:(UIScrollView *) scrollView;

/**
 Asks the data source for the title to be used for the specified button state.
 The dataset uses a fixed font style by default, if no attributes are set. If you want a different font style, return a attributed string.
 
 @param scrollView A scrollView subclass object informing the data source.
 @param state The state that uses the specified title. The possible values are described in UIControlState.
 @return An attributed string for the dataset button title, combining font, text color, text pararaph style, etc.
 */
- (NSAttributedString *)buttonTitleForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state;

/**
 Asks the data source for the image to be used for the specified button state.
 This method will override buttonTitleForEmptyDataSet:forState: and present the image only without any text.
 
 @param scrollView A scrollView subclass object informing the data source.
 @param state The state that uses the specified title. The possible values are described in UIControlState.
 @return An image for the dataset button imageview.
 */
- (UIImage *)buttonImageForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state;

/**
 Asks the data source for a background image to be used for the specified button state.
 There is no default style for this call.
 
 @param scrollView A scrollView subclass informing the data source.
 @param state The state that uses the specified image. The values are described in UIControlState.
 @return An attributed string for the dataset button title, combining font, text color, text pararaph style, etc.
 */
- (UIImage *)buttonBackgroundImageForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state;

/**
 Asks the data source for the background color of the dataset. Default is clear color.
 
 @param scrollView A scrollView subclass object informing the data source.
 @return A color to be applied to the dataset background view.
 */
- (UIColor *)backgroundColorForEmptyDataSet:(UIScrollView *)scrollView;

/**
 Asks the data source for a custom view to be displayed instead of the default views such as labels, imageview and button. Default is nil.
 Use this method to show an activity view indicator for loading feedback, or for complete custom empty data set.
 Returning a custom view will ignore -offsetForEmptyDataSet and -spaceHeightForEmptyDataSet configurations.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return The custom view.
 */
- (UIView *)customViewForEmptyDataSet:(UIScrollView *)scrollView;

/**
 Asks the data source for a offset for vertical and horizontal alignment of the content. Default is CGPointZero.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return The offset for vertical and horizontal alignment.
 */
- (CGPoint)offsetForEmptyDataSet:(UIScrollView *)scrollView DZNEmptyDataSetDeprecated(-verticalOffsetForEmptyDataSet:);
- (CGFloat)verticalOffsetForEmptyDataSet:(UIScrollView *)scrollView;

/**
 Asks the data source for a vertical space between elements. Default is 11 pts.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return The space height between elements.
 */
- (CGFloat)spaceHeightForEmptyDataSet:(UIScrollView *)scrollView;

@end


/**
 The object that acts as the delegate of the empty datasets.
 @discussion The delegate can adopt the DZNEmptyDataSetDelegate protocol. The delegate is not retained. All delegate methods are optional.
 
 @discussion All delegate methods are optional. Use this delegate for receiving action callbacks.
 */
@protocol DZNEmptyDataSetDelegate <NSObject>
@optional

/**
 Asks the delegate to know if the empty dataset should fade in when displayed. Default is YES.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if the empty dataset should fade in.
 */
- (BOOL)emptyDataSetShouldFadeIn:(UIScrollView *)scrollView;

/**
 Asks the delegate to know if the empty dataset should still be displayed when the amount of items is more than 0. Default is NO
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if empty dataset should be forced to display
 */
- (BOOL)emptyDataSetShouldBeForcedToDisplay:(UIScrollView *)scrollView;

/**
 Asks the delegate to know if the empty dataset should be rendered and displayed. Default is YES.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if the empty dataset should show.
 */
- (BOOL)emptyDataSetShouldDisplay:(UIScrollView *)scrollView;

/**
 Asks the delegate for touch permission. Default is YES.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if the empty dataset receives touch gestures.
 */
- (BOOL)emptyDataSetShouldAllowTouch:(UIScrollView *)scrollView;

/**
 Asks the delegate for scroll permission. Default is NO.
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if the empty dataset is allowed to be scrollable.
 */
- (BOOL)emptyDataSetShouldAllowScroll:(UIScrollView *)scrollView;

/**
 Asks the delegate for image view animation permission. Default is NO.
 Make sure to return a valid CAAnimation object from imageAnimationForEmptyDataSet:
 
 @param scrollView A scrollView subclass object informing the delegate.
 @return YES if the empty dataset is allowed to animate
 */
- (BOOL)emptyDataSetShouldAnimateImageView:(UIScrollView *)scrollView;

/**
 Tells the delegate that the empty dataset view was tapped.
 Use this method either to resignFirstResponder of a textfield or searchBar.
 
 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetDidTapView:(UIScrollView *)scrollView DZNEmptyDataSetDeprecated(-emptyDataSet:didTapView:);

/**
 Tells the delegate that the action button was tapped.
 
 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetDidTapButton:(UIScrollView *)scrollView DZNEmptyDataSetDeprecated(-emptyDataSet:didTapButton:);

/**
 Tells the delegate that the empty dataset view was tapped.
 Use this method either to resignFirstResponder of a textfield or searchBar.
 
 @param scrollView A scrollView subclass informing the delegate.
 @param view the view tapped by the user
 */
- (void)emptyDataSet:(UIScrollView *)scrollView didTapView:(UIView *)view;

/**
 Tells the delegate that the action button was tapped.
 
 @param scrollView A scrollView subclass informing the delegate.
 @param button the button tapped by the user
 */
- (void)emptyDataSet:(UIScrollView *)scrollView didTapButton:(UIButton *)button;

/**
 Tells the delegate that the empty data set will appear.

 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetWillAppear:(UIScrollView *)scrollView;

/**
 Tells the delegate that the empty data set did appear.

 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetDidAppear:(UIScrollView *)scrollView;

/**
 Tells the delegate that the empty data set will disappear.

 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetWillDisappear:(UIScrollView *)scrollView;

/**
 Tells the delegate that the empty data set did disappear.

 @param scrollView A scrollView subclass informing the delegate.
 */
- (void)emptyDataSetDidDisappear:(UIScrollView *)scrollView;

@end

#undef DZNEmptyDataSetDeprecated

UIScrollView+EmptyDataSet.m

#import "UIScrollView+EmptyDataSet.h"
#import <objc/runtime.h>

@interface UIView (DZNConstraintBasedLayoutExtensions)

- (NSLayoutConstraint *)equallyRelatedConstraintWithView:(UIView *)view attribute:(NSLayoutAttribute)attribute;

@end

@interface DZNWeakObjectContainer : NSObject

@property (nonatomic, readonly, weak) id weakObject;

- (instancetype)initWithWeakObject:(id)object;

@end

@interface DZNEmptyDataSetView : UIView

@property (nonatomic, readonly) UIView *contentView;
@property (nonatomic, readonly) UILabel *titleLabel;
@property (nonatomic, readonly) UILabel *detailLabel;
@property (nonatomic, readonly) UIImageView *imageView;
@property (nonatomic, readonly) UIButton *button;
@property (nonatomic, strong) UIView *customView;
@property (nonatomic, strong) UITapGestureRecognizer *tapGesture;

@property (nonatomic, assign) CGFloat verticalOffset;
@property (nonatomic, assign) CGFloat verticalSpace;

@property (nonatomic, assign) BOOL fadeInOnDisplay;

- (void)setupConstraints;
- (void)prepareForReuse;

@end


#pragma mark - UIScrollView+EmptyDataSet

static char const * const kEmptyDataSetSource =     "emptyDataSetSource";
static char const * const kEmptyDataSetDelegate =   "emptyDataSetDelegate";
static char const * const kEmptyDataSetView =       "emptyDataSetView";

#define kEmptyImageViewAnimationKey @"com.dzn.emptyDataSet.imageViewAnimation"

@interface UIScrollView () <UIGestureRecognizerDelegate>
@property (nonatomic, readonly) DZNEmptyDataSetView *emptyDataSetView;
@end

@implementation UIScrollView (DZNEmptyDataSet)

#pragma mark - Getters (Public)

- (id<DZNEmptyDataSetSource>)emptyDataSetSource
{
    DZNWeakObjectContainer *container = objc_getAssociatedObject(self, kEmptyDataSetSource);
    return container.weakObject;
}

- (id<DZNEmptyDataSetDelegate>)emptyDataSetDelegate
{
    DZNWeakObjectContainer *container = objc_getAssociatedObject(self, kEmptyDataSetDelegate);
    return container.weakObject;
}

- (BOOL)isEmptyDataSetVisible
{
    UIView *view = objc_getAssociatedObject(self, kEmptyDataSetView);
    return view ? !view.hidden : NO;
}

#pragma mark - Getters (Private)

- (DZNEmptyDataSetView *)emptyDataSetView
{
    DZNEmptyDataSetView *view = objc_getAssociatedObject(self, kEmptyDataSetView);
    
    if (!view)
    {
        view = [DZNEmptyDataSetView new];
        view.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;
        view.hidden = YES;
        
        view.tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(dzn_didTapContentView:)];
        view.tapGesture.delegate = self;
        [view addGestureRecognizer:view.tapGesture];
        
        [self setEmptyDataSetView:view];
    }
    return view;
}

- (BOOL)dzn_canDisplay
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource conformsToProtocol:@protocol(DZNEmptyDataSetSource)]) {
        if ([self isKindOfClass:[UITableView class]] || [self isKindOfClass:[UICollectionView class]] || [self isKindOfClass:[UIScrollView class]]) {
            return YES;
        }
    }
    
    return NO;
}

- (NSInteger)dzn_itemsCount
{
    NSInteger items = 0;
    
    // UIScollView doesn't respond to 'dataSource' so let's exit
    if (![self respondsToSelector:@selector(dataSource)]) {
        return items;
    }
    
    // UITableView support
    if ([self isKindOfClass:[UITableView class]]) {
        
        UITableView *tableView = (UITableView *)self;
        id <UITableViewDataSource> dataSource = tableView.dataSource;
        
        NSInteger sections = 1;
        
        if (dataSource && [dataSource respondsToSelector:@selector(numberOfSectionsInTableView:)]) {
            sections = [dataSource numberOfSectionsInTableView:tableView];
        }
        
        if (dataSource && [dataSource respondsToSelector:@selector(tableView:numberOfRowsInSection:)]) {
            for (NSInteger section = 0; section < sections; section++) {
                items += [dataSource tableView:tableView numberOfRowsInSection:section];
            }
        }
    }
    // UICollectionView support
    else if ([self isKindOfClass:[UICollectionView class]]) {
        
        UICollectionView *collectionView = (UICollectionView *)self;
        id <UICollectionViewDataSource> dataSource = collectionView.dataSource;

        NSInteger sections = 1;
        
        if (dataSource && [dataSource respondsToSelector:@selector(numberOfSectionsInCollectionView:)]) {
            sections = [dataSource numberOfSectionsInCollectionView:collectionView];
        }
        
        if (dataSource && [dataSource respondsToSelector:@selector(collectionView:numberOfItemsInSection:)]) {
            for (NSInteger section = 0; section < sections; section++) {
                items += [dataSource collectionView:collectionView numberOfItemsInSection:section];
            }
        }
    }
    
    return items;
}


#pragma mark - Data Source Getters

- (NSAttributedString *)dzn_titleLabelString
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(titleForEmptyDataSet:)]) {
        NSAttributedString *string = [self.emptyDataSetSource titleForEmptyDataSet:self];
        if (string) NSAssert([string isKindOfClass:[NSAttributedString class]], @"You must return a valid NSAttributedString object for -titleForEmptyDataSet:");
        return string;
    }
    return nil;
}

- (NSAttributedString *)dzn_detailLabelString
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(descriptionForEmptyDataSet:)]) {
        NSAttributedString *string = [self.emptyDataSetSource descriptionForEmptyDataSet:self];
        if (string) NSAssert([string isKindOfClass:[NSAttributedString class]], @"You must return a valid NSAttributedString object for -descriptionForEmptyDataSet:");
        return string;
    }
    return nil;
}

- (UIImage *)dzn_image
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(imageForEmptyDataSet:)]) {
        UIImage *image = [self.emptyDataSetSource imageForEmptyDataSet:self];
        if (image) NSAssert([image isKindOfClass:[UIImage class]], @"You must return a valid UIImage object for -imageForEmptyDataSet:");
        return image;
    }
    return nil;
}

- (CAAnimation *)dzn_imageAnimation
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(imageAnimationForEmptyDataSet:)]) {
        CAAnimation *imageAnimation = [self.emptyDataSetSource imageAnimationForEmptyDataSet:self];
        if (imageAnimation) NSAssert([imageAnimation isKindOfClass:[CAAnimation class]], @"You must return a valid CAAnimation object for -imageAnimationForEmptyDataSet:");
        return imageAnimation;
    }
    return nil;
}

- (UIColor *)dzn_imageTintColor
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(imageTintColorForEmptyDataSet:)]) {
        UIColor *color = [self.emptyDataSetSource imageTintColorForEmptyDataSet:self];
        if (color) NSAssert([color isKindOfClass:[UIColor class]], @"You must return a valid UIColor object for -imageTintColorForEmptyDataSet:");
        return color;
    }
    return nil;
}

- (NSAttributedString *)dzn_buttonTitleForState:(UIControlState)state
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(buttonTitleForEmptyDataSet:forState:)]) {
        NSAttributedString *string = [self.emptyDataSetSource buttonTitleForEmptyDataSet:self forState:state];
        if (string) NSAssert([string isKindOfClass:[NSAttributedString class]], @"You must return a valid NSAttributedString object for -buttonTitleForEmptyDataSet:forState:");
        return string;
    }
    return nil;
}

- (UIImage *)dzn_buttonImageForState:(UIControlState)state
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(buttonImageForEmptyDataSet:forState:)]) {
        UIImage *image = [self.emptyDataSetSource buttonImageForEmptyDataSet:self forState:state];
        if (image) NSAssert([image isKindOfClass:[UIImage class]], @"You must return a valid UIImage object for -buttonImageForEmptyDataSet:forState:");
        return image;
    }
    return nil;
}

- (UIImage *)dzn_buttonBackgroundImageForState:(UIControlState)state
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(buttonBackgroundImageForEmptyDataSet:forState:)]) {
        UIImage *image = [self.emptyDataSetSource buttonBackgroundImageForEmptyDataSet:self forState:state];
        if (image) NSAssert([image isKindOfClass:[UIImage class]], @"You must return a valid UIImage object for -buttonBackgroundImageForEmptyDataSet:forState:");
        return image;
    }
    return nil;
}

- (UIColor *)dzn_dataSetBackgroundColor
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(backgroundColorForEmptyDataSet:)]) {
        UIColor *color = [self.emptyDataSetSource backgroundColorForEmptyDataSet:self];
        if (color) NSAssert([color isKindOfClass:[UIColor class]], @"You must return a valid UIColor object for -backgroundColorForEmptyDataSet:");
        return color;
    }
    return [UIColor clearColor];
}

- (UIView *)dzn_customView
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(customViewForEmptyDataSet:)]) {
        UIView *view = [self.emptyDataSetSource customViewForEmptyDataSet:self];
        if (view) NSAssert([view isKindOfClass:[UIView class]], @"You must return a valid UIView object for -customViewForEmptyDataSet:");
        return view;
    }
    return nil;
}

- (CGFloat)dzn_verticalOffset
{
    CGFloat offset = 0.0;
    
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(verticalOffsetForEmptyDataSet:)]) {
        offset = [self.emptyDataSetSource verticalOffsetForEmptyDataSet:self];
    }
    return offset;
}

- (CGFloat)dzn_verticalSpace
{
    if (self.emptyDataSetSource && [self.emptyDataSetSource respondsToSelector:@selector(spaceHeightForEmptyDataSet:)]) {
        return [self.emptyDataSetSource spaceHeightForEmptyDataSet:self];
    }
    return 0.0;
}


#pragma mark - Delegate Getters & Events (Private)

- (BOOL)dzn_shouldFadeIn {
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldFadeIn:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldFadeIn:self];
    }
    return YES;
}

- (BOOL)dzn_shouldDisplay
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldDisplay:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldDisplay:self];
    }
    return YES;
}

- (BOOL)dzn_shouldBeForcedToDisplay
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldBeForcedToDisplay:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldBeForcedToDisplay:self];
    }
    return NO;
}

- (BOOL)dzn_isTouchAllowed
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldAllowTouch:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldAllowTouch:self];
    }
    return YES;
}

- (BOOL)dzn_isScrollAllowed
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldAllowScroll:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldAllowScroll:self];
    }
    return NO;
}

- (BOOL)dzn_isImageViewAnimateAllowed
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetShouldAnimateImageView:)]) {
        return [self.emptyDataSetDelegate emptyDataSetShouldAnimateImageView:self];
    }
    return NO;
}

- (void)dzn_willAppear
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetWillAppear:)]) {
        [self.emptyDataSetDelegate emptyDataSetWillAppear:self];
    }
}

- (void)dzn_didAppear
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetDidAppear:)]) {
        [self.emptyDataSetDelegate emptyDataSetDidAppear:self];
    }
}

- (void)dzn_willDisappear
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetWillDisappear:)]) {
        [self.emptyDataSetDelegate emptyDataSetWillDisappear:self];
    }
}

- (void)dzn_didDisappear
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetDidDisappear:)]) {
        [self.emptyDataSetDelegate emptyDataSetDidDisappear:self];
    }
}

- (void)dzn_didTapContentView:(id)sender
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSet:didTapView:)]) {
        [self.emptyDataSetDelegate emptyDataSet:self didTapView:sender];
    }
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    else if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetDidTapView:)]) {
        [self.emptyDataSetDelegate emptyDataSetDidTapView:self];
    }
#pragma clang diagnostic pop
}

- (void)dzn_didTapDataButton:(id)sender
{
    if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSet:didTapButton:)]) {
        [self.emptyDataSetDelegate emptyDataSet:self didTapButton:sender];
    }
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    else if (self.emptyDataSetDelegate && [self.emptyDataSetDelegate respondsToSelector:@selector(emptyDataSetDidTapButton:)]) {
        [self.emptyDataSetDelegate emptyDataSetDidTapButton:self];
    }
#pragma clang diagnostic pop
}


#pragma mark - Setters (Public)

- (void)setEmptyDataSetSource:(id<DZNEmptyDataSetSource>)datasource
{
    if (!datasource || ![self dzn_canDisplay]) {
        [self dzn_invalidate];
    }
    
    objc_setAssociatedObject(self, kEmptyDataSetSource, [[DZNWeakObjectContainer alloc] initWithWeakObject:datasource], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    
    // We add method sizzling for injecting -dzn_reloadData implementation to the native -reloadData implementation
    [self swizzleIfPossible:@selector(reloadData)];
    
    // Exclusively for UITableView, we also inject -dzn_reloadData to -endUpdates
    if ([self isKindOfClass:[UITableView class]]) {
        [self swizzleIfPossible:@selector(endUpdates)];
    }
}

- (void)setEmptyDataSetDelegate:(id<DZNEmptyDataSetDelegate>)delegate
{
    if (!delegate) {
        [self dzn_invalidate];
    }
    
    objc_setAssociatedObject(self, kEmptyDataSetDelegate, [[DZNWeakObjectContainer alloc] initWithWeakObject:delegate], OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}


#pragma mark - Setters (Private)

- (void)setEmptyDataSetView:(DZNEmptyDataSetView *)view
{
    objc_setAssociatedObject(self, kEmptyDataSetView, view, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}


#pragma mark - Reload APIs (Public)

- (void)reloadEmptyDataSet
{
    [self dzn_reloadEmptyDataSet];
}


#pragma mark - Reload APIs (Private)

- (void)dzn_reloadEmptyDataSet
{
    if (![self dzn_canDisplay]) {
        return;
    }
    
    if (([self dzn_shouldDisplay] && [self dzn_itemsCount] == 0) || [self dzn_shouldBeForcedToDisplay])
    {
        // Notifies that the empty dataset view will appear
        [self dzn_willAppear];
        
        DZNEmptyDataSetView *view = self.emptyDataSetView;
        
        if (!view.superview) {
            // Send the view all the way to the back, in case a header and/or footer is present, as well as for sectionHeaders or any other content
            if (([self isKindOfClass:[UITableView class]] || [self isKindOfClass:[UICollectionView class]]) && self.subviews.count > 1) {
                [self insertSubview:view atIndex:0];
            }
            else {
                [self addSubview:view];
            }
        }
        
        // Removing view resetting the view and its constraints it very important to guarantee a good state
        [view prepareForReuse];
        
        UIView *customView = [self dzn_customView];
        
        // If a non-nil custom view is available, let's configure it instead
        if (customView) {
            view.customView = customView;
        }
        else {
            // Get the data from the data source
            NSAttributedString *titleLabelString = [self dzn_titleLabelString];
            NSAttributedString *detailLabelString = [self dzn_detailLabelString];
            
            UIImage *buttonImage = [self dzn_buttonImageForState:UIControlStateNormal];
            NSAttributedString *buttonTitle = [self dzn_buttonTitleForState:UIControlStateNormal];
            
            UIImage *image = [self dzn_image];
            UIColor *imageTintColor = [self dzn_imageTintColor];
            UIImageRenderingMode renderingMode = imageTintColor ? UIImageRenderingModeAlwaysTemplate : UIImageRenderingModeAlwaysOriginal;
            
            view.verticalSpace = [self dzn_verticalSpace];
            
            // Configure Image
            if (image) {
                if ([image respondsToSelector:@selector(imageWithRenderingMode:)]) {
                    view.imageView.image = [image imageWithRenderingMode:renderingMode];
                    view.imageView.tintColor = imageTintColor;
                }
                else {
                    // iOS 6 fallback: insert code to convert imaged if needed
                    view.imageView.image = image;
                }
            }
            
            // Configure title label
            if (titleLabelString) {
                view.titleLabel.attributedText = titleLabelString;
            }
            
            // Configure detail label
            if (detailLabelString) {
                view.detailLabel.attributedText = detailLabelString;
            }
            
            // Configure button
            if (buttonImage) {
                [view.button setImage:buttonImage forState:UIControlStateNormal];
                [view.button setImage:[self dzn_buttonImageForState:UIControlStateHighlighted] forState:UIControlStateHighlighted];
            }
            else if (buttonTitle) {
                [view.button setAttributedTitle:buttonTitle forState:UIControlStateNormal];
                [view.button setAttributedTitle:[self dzn_buttonTitleForState:UIControlStateHighlighted] forState:UIControlStateHighlighted];
                [view.button setBackgroundImage:[self dzn_buttonBackgroundImageForState:UIControlStateNormal] forState:UIControlStateNormal];
                [view.button setBackgroundImage:[self dzn_buttonBackgroundImageForState:UIControlStateHighlighted] forState:UIControlStateHighlighted];
            }
        }
        
        // Configure offset
        view.verticalOffset = [self dzn_verticalOffset];
        
        // Configure the empty dataset view
        view.backgroundColor = [self dzn_dataSetBackgroundColor];
        view.hidden = NO;
        view.clipsToBounds = YES;
        
        // Configure empty dataset userInteraction permission
        view.userInteractionEnabled = [self dzn_isTouchAllowed];
        
        // Configure empty dataset fade in display
        view.fadeInOnDisplay = [self dzn_shouldFadeIn];
        
        [view setupConstraints];
        
        [UIView performWithoutAnimation:^{
            [view layoutIfNeeded];            
        }];
        
        // Configure scroll permission
        self.scrollEnabled = [self dzn_isScrollAllowed];
        
        // Configure image view animation
        if ([self dzn_isImageViewAnimateAllowed])
        {
            CAAnimation *animation = [self dzn_imageAnimation];
            
            if (animation) {
                [self.emptyDataSetView.imageView.layer addAnimation:animation forKey:kEmptyImageViewAnimationKey];
            }
        }
        else if ([self.emptyDataSetView.imageView.layer animationForKey:kEmptyImageViewAnimationKey]) {
            [self.emptyDataSetView.imageView.layer removeAnimationForKey:kEmptyImageViewAnimationKey];
        }
        
        // Notifies that the empty dataset view did appear
        [self dzn_didAppear];
    }
    else if (self.isEmptyDataSetVisible) {
        [self dzn_invalidate];
    }
}

- (void)dzn_invalidate
{
    // Notifies that the empty dataset view will disappear
    [self dzn_willDisappear];
    
    if (self.emptyDataSetView) {
        [self.emptyDataSetView prepareForReuse];
        [self.emptyDataSetView removeFromSuperview];
        
        [self setEmptyDataSetView:nil];
    }
    
    self.scrollEnabled = YES;
    
    // Notifies that the empty dataset view did disappear
    [self dzn_didDisappear];
}


#pragma mark - Method Swizzling

static NSMutableDictionary *_impLookupTable;
static NSString *const DZNSwizzleInfoPointerKey = @"pointer";
static NSString *const DZNSwizzleInfoOwnerKey = @"owner";
static NSString *const DZNSwizzleInfoSelectorKey = @"selector";

// Based on Bryce Buchanan's swizzling technique http://blog.newrelic.com/2014/04/16/right-way-to-swizzle/
// And Juzzin's ideas https://github.com/juzzin/JUSEmptyViewController

void dzn_original_implementation(id self, SEL _cmd)
{
    // Fetch original implementation from lookup table
    Class baseClass = dzn_baseClassToSwizzleForTarget(self);
    NSString *key = dzn_implementationKey(baseClass, _cmd);
    
    NSDictionary *swizzleInfo = [_impLookupTable objectForKey:key];
    NSValue *impValue = [swizzleInfo valueForKey:DZNSwizzleInfoPointerKey];
    
    IMP impPointer = [impValue pointerValue];
    
    // We then inject the additional implementation for reloading the empty dataset
    // Doing it before calling the original implementation does update the 'isEmptyDataSetVisible' flag on time.
    [self dzn_reloadEmptyDataSet];
    
    // If found, call original implementation
    if (impPointer) {
        ((void(*)(id,SEL))impPointer)(self,_cmd);
    }
}

NSString *dzn_implementationKey(Class class, SEL selector)
{
    if (!class || !selector) {
        return nil;
    }
    
    NSString *className = NSStringFromClass([class class]);
    
    NSString *selectorName = NSStringFromSelector(selector);
    return [NSString stringWithFormat:@"%@_%@",className,selectorName];
}

Class dzn_baseClassToSwizzleForTarget(id target)
{
    if ([target isKindOfClass:[UITableView class]]) {
        return [UITableView class];
    }
    else if ([target isKindOfClass:[UICollectionView class]]) {
        return [UICollectionView class];
    }
    else if ([target isKindOfClass:[UIScrollView class]]) {
        return [UIScrollView class];
    }
    
    return nil;
}

- (void)swizzleIfPossible:(SEL)selector
{
    // Check if the target responds to selector
    if (![self respondsToSelector:selector]) {
        return;
    }
    
    // Create the lookup table
    if (!_impLookupTable) {
        _impLookupTable = [[NSMutableDictionary alloc] initWithCapacity:3]; // 3 represent the supported base classes
    }
    
    // We make sure that setImplementation is called once per class kind, UITableView or UICollectionView.
    for (NSDictionary *info in [_impLookupTable allValues]) {
        Class class = [info objectForKey:DZNSwizzleInfoOwnerKey];
        NSString *selectorName = [info objectForKey:DZNSwizzleInfoSelectorKey];
        
        if ([selectorName isEqualToString:NSStringFromSelector(selector)]) {
            if ([self isKindOfClass:class]) {
                return;
            }
        }
    }
    
    Class baseClass = dzn_baseClassToSwizzleForTarget(self);
    NSString *key = dzn_implementationKey(baseClass, selector);
    NSValue *impValue = [[_impLookupTable objectForKey:key] valueForKey:DZNSwizzleInfoPointerKey];
    
    // If the implementation for this class already exist, skip!!
    if (impValue || !key || !baseClass) {
        return;
    }
    
    // Swizzle by injecting additional implementation
    Method method = class_getInstanceMethod(baseClass, selector);
    IMP dzn_newImplementation = method_setImplementation(method, (IMP)dzn_original_implementation);
    
    // Store the new implementation in the lookup table
    NSDictionary *swizzledInfo = @{DZNSwizzleInfoOwnerKey: baseClass,
                                   DZNSwizzleInfoSelectorKey: NSStringFromSelector(selector),
                                   DZNSwizzleInfoPointerKey: [NSValue valueWithPointer:dzn_newImplementation]};
    
    [_impLookupTable setObject:swizzledInfo forKey:key];
}


#pragma mark - UIGestureRecognizerDelegate Methods

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    if ([gestureRecognizer.view isEqual:self.emptyDataSetView]) {
        return [self dzn_isTouchAllowed];
    }
    
    return [super gestureRecognizerShouldBegin:gestureRecognizer];
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    UIGestureRecognizer *tapGesture = self.emptyDataSetView.tapGesture;
    
    if ([gestureRecognizer isEqual:tapGesture] || [otherGestureRecognizer isEqual:tapGesture]) {
        return YES;
    }
    
    // defer to emptyDataSetDelegate's implementation if available
    if ( (self.emptyDataSetDelegate != (id)self) && [self.emptyDataSetDelegate respondsToSelector:@selector(gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:)]) {
        return [(id)self.emptyDataSetDelegate gestureRecognizer:gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:otherGestureRecognizer];
    }
    
    return NO;
}

@end


#pragma mark - DZNEmptyDataSetView

@interface DZNEmptyDataSetView ()
@end

@implementation DZNEmptyDataSetView
@synthesize contentView = _contentView;
@synthesize titleLabel = _titleLabel, detailLabel = _detailLabel, imageView = _imageView, button = _button;

#pragma mark - Initialization Methods

- (instancetype)init
{
    self =  [super init];
    if (self) {
        [self addSubview:self.contentView];
    }
    return self;
}

- (void)didMoveToSuperview
{
    self.frame = self.superview.bounds;
    
    void(^fadeInBlock)(void) = ^{_contentView.alpha = 1.0;};
    
    if (self.fadeInOnDisplay) {
        [UIView animateWithDuration:0.25
                         animations:fadeInBlock
                         completion:NULL];
    }
    else {
        fadeInBlock();
    }
}


#pragma mark - Getters

- (UIView *)contentView
{
    if (!_contentView)
    {
        _contentView = [UIView new];
        _contentView.translatesAutoresizingMaskIntoConstraints = NO;
        _contentView.backgroundColor = [UIColor clearColor];
        _contentView.userInteractionEnabled = YES;
        _contentView.alpha = 0;
    }
    return _contentView;
}

- (UIImageView *)imageView
{
    if (!_imageView)
    {
        _imageView = [UIImageView new];
        _imageView.translatesAutoresizingMaskIntoConstraints = NO;
        _imageView.backgroundColor = [UIColor clearColor];
        _imageView.contentMode = UIViewContentModeScaleAspectFit;
        _imageView.userInteractionEnabled = NO;
        _imageView.accessibilityIdentifier = @"empty set background image";
        
        [_contentView addSubview:_imageView];
    }
    return _imageView;
}

- (UILabel *)titleLabel
{
    if (!_titleLabel)
    {
        _titleLabel = [UILabel new];
        _titleLabel.translatesAutoresizingMaskIntoConstraints = NO;
        _titleLabel.backgroundColor = [UIColor clearColor];
        
        _titleLabel.font = [UIFont systemFontOfSize:27.0];
        _titleLabel.textColor = [UIColor colorWithWhite:0.6 alpha:1.0];
        _titleLabel.textAlignment = NSTextAlignmentCenter;
        _titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
        _titleLabel.numberOfLines = 0;
        _titleLabel.accessibilityIdentifier = @"empty set title";
        
        [_contentView addSubview:_titleLabel];
    }
    return _titleLabel;
}

- (UILabel *)detailLabel
{
    if (!_detailLabel)
    {
        _detailLabel = [UILabel new];
        _detailLabel.translatesAutoresizingMaskIntoConstraints = NO;
        _detailLabel.backgroundColor = [UIColor clearColor];
        
        _detailLabel.font = [UIFont systemFontOfSize:17.0];
        _detailLabel.textColor = [UIColor colorWithWhite:0.6 alpha:1.0];
        _detailLabel.textAlignment = NSTextAlignmentCenter;
        _detailLabel.lineBreakMode = NSLineBreakByWordWrapping;
        _detailLabel.numberOfLines = 0;
        _detailLabel.accessibilityIdentifier = @"empty set detail label";
        
        [_contentView addSubview:_detailLabel];
    }
    return _detailLabel;
}

- (UIButton *)button
{
    if (!_button)
    {
        _button = [UIButton buttonWithType:UIButtonTypeCustom];
        _button.translatesAutoresizingMaskIntoConstraints = NO;
        _button.backgroundColor = [UIColor clearColor];
        _button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;
        _button.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
        _button.accessibilityIdentifier = @"empty set button";
        
        [_button addTarget:self action:@selector(didTapButton:) forControlEvents:UIControlEventTouchUpInside];
        _button.layer.masksToBounds = YES;
        _button.layer.borderWidth = 1.f;
        _button.layer.cornerRadius = 45.0/2;
        _button.layer.borderColor = ColorWithAlpha(235, 67, 57, 1).CGColor;
        [_contentView addSubview:_button];
        [_button mas_makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(@180);
            make.centerX.equalTo(self.contentView.mas_centerX);
        }];
        
    }
    return _button;
}

- (BOOL)canShowImage
{
    return (_imageView.image && _imageView.superview);
}

- (BOOL)canShowTitle
{
    return (_titleLabel.attributedText.string.length > 0 && _titleLabel.superview);
}

- (BOOL)canShowDetail
{
    return (_detailLabel.attributedText.string.length > 0 && _detailLabel.superview);
}

- (BOOL)canShowButton
{
    if ([_button attributedTitleForState:UIControlStateNormal].string.length > 0 || [_button imageForState:UIControlStateNormal]) {
        return (_button.superview != nil);
    }
    return NO;
}


#pragma mark - Setters

- (void)setCustomView:(UIView *)view
{
    if (!view) {
        return;
    }
    
    if (_customView) {
        [_customView removeFromSuperview];
        _customView = nil;
    }
    
    _customView = view;
    _customView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.contentView addSubview:_customView];
}


#pragma mark - Action Methods

- (void)didTapButton:(id)sender
{
    SEL selector = NSSelectorFromString(@"dzn_didTapDataButton:");
    
    if ([self.superview respondsToSelector:selector]) {
        [self.superview performSelector:selector withObject:sender afterDelay:0.0f];
    }
}

- (void)removeAllConstraints
{
    [self removeConstraints:self.constraints];
    [_contentView removeConstraints:_contentView.constraints];
}

- (void)prepareForReuse
{
    [self.contentView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    
    _titleLabel = nil;
    _detailLabel = nil;
    _imageView = nil;
    _button = nil;
    _customView = nil;
    
    [self removeAllConstraints];
}


#pragma mark - Auto-Layout Configuration

- (void)setupConstraints
{
    // First, configure the content view constaints
    // The content view must alway be centered to its superview
    
    //水平居中
    NSLayoutConstraint *centerXConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeCenterX];
    
    //顶部对齐
    NSLayoutConstraint *centerYConstraint = [self equallyRelatedConstraintWithView:self.contentView attribute:NSLayoutAttributeTop];
    
    [self addConstraint:centerXConstraint];
    [self addConstraint:centerYConstraint];
    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[contentView]|" options:0 metrics:nil views:@{@"contentView": self.contentView}]];
    
    // When a custom offset is available, we adjust the vertical constraints' constants
    if (self.verticalOffset != 0 && self.constraints.count > 0) {
        centerYConstraint.constant = self.verticalOffset;
    }
    
    // If applicable, set the custom view's constraints
    if (_customView) {
        [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[customView]|" options:0 metrics:nil views:@{@"customView":_customView}]];
        [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[customView]|" options:0 metrics:nil views:@{@"customView":_customView}]];
    }
    else {
        CGFloat width = CGRectGetWidth(self.frame) ? : CGRectGetWidth([UIScreen mainScreen].bounds);
        CGFloat padding = roundf(width/16.0);
        CGFloat verticalSpace = self.verticalSpace ? : 11.0; // Default is 11 pts
        
        NSMutableArray *subviewStrings = [NSMutableArray array];
        NSMutableDictionary *views = [NSMutableDictionary dictionary];
        NSDictionary *metrics = @{@"padding": @(padding)};
        
        // Assign the image view's horizontal constraints
        if (_imageView.superview) {
            
            [subviewStrings addObject:@"imageView"];
            views[[subviewStrings lastObject]] = _imageView;
            
            [self.contentView addConstraint:[self.contentView equallyRelatedConstraintWithView:_imageView attribute:NSLayoutAttributeCenterX]];
        }
        
        // Assign the title label's horizontal constraints
        if ([self canShowTitle]) {
            
            [subviewStrings addObject:@"titleLabel"];
            views[[subviewStrings lastObject]] = _titleLabel;
            
            [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(padding@750)-[titleLabel(>=0)]-(padding@750)-|"
                                                                                     options:0 metrics:metrics views:views]];
        }
        // or removes from its superview
        else {
            [_titleLabel removeFromSuperview];
            _titleLabel = nil;
        }
        
        // Assign the detail label's horizontal constraints
        if ([self canShowDetail]) {
            
            [subviewStrings addObject:@"detailLabel"];
            views[[subviewStrings lastObject]] = _detailLabel;
            
            [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(padding@750)-[detailLabel(>=0)]-(padding@750)-|"
                                                                                     options:0 metrics:metrics views:views]];
        }
        // or removes from its superview
        else {
            [_detailLabel removeFromSuperview];
            _detailLabel = nil;
        }
        
        // Assign the button's horizontal constraints
        if ([self canShowButton]) {
            
            [subviewStrings addObject:@"button"];
            views[[subviewStrings lastObject]] = _button;
            
            [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(padding@750)-[button(>=0)]-(padding@750)-|"
                                                                                     options:0 metrics:metrics views:views]];
        }
        // or removes from its superview
        else {
            [_button removeFromSuperview];
            _button = nil;
        }
        
        
        NSMutableString *verticalFormat = [NSMutableString new];
        
        // Build a dynamic string format for the vertical constraints, adding a margin between each element. Default is 11 pts.
        for (int i = 0; i < subviewStrings.count; i++) {
            
            NSString *string = subviewStrings[i];
            [verticalFormat appendFormat:@"[%@]", string];
            
            if (i < subviewStrings.count-1) {
                [verticalFormat appendFormat:@"-(%.f@750)-", verticalSpace];
            }
        }
        
        // Assign the vertical constraints to the content view
        if (verticalFormat.length > 0) {
            [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"V:|%@|", verticalFormat]
                                                                                     options:0 metrics:metrics views:views]];
        }
    }
}

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    UIView *hitView = [super hitTest:point withEvent:event];
    
    // Return any UIControl instance such as buttons, segmented controls, switches, etc.
    if ([hitView isKindOfClass:[UIControl class]]) {
        return hitView;
    }
    
    // Return either the contentView or customView
    if ([hitView isEqual:_contentView] || [hitView isEqual:_customView]) {
        return hitView;
    }
    
    return nil;
}

@end


#pragma mark - UIView+DZNConstraintBasedLayoutExtensions

@implementation UIView (DZNConstraintBasedLayoutExtensions)

- (NSLayoutConstraint *)equallyRelatedConstraintWithView:(UIView *)view attribute:(NSLayoutAttribute)attribute
{
    return [NSLayoutConstraint constraintWithItem:view
                                        attribute:attribute
                                        relatedBy:NSLayoutRelationEqual
                                           toItem:self
                                        attribute:attribute
                                       multiplier:1.0
                                         constant:0.0];
}

@end

#pragma mark - DZNWeakObjectContainer

@implementation DZNWeakObjectContainer

- (instancetype)initWithWeakObject:(id)object
{
    self = [super init];
    if (self) {
        _weakObject = object;
    }
    return self;
}

@end