App经常在tableView没有数据的时候需要显示，占位图，和暂无数据的文字，如下图一样

FzM7fm2.png!web.png

github链接： https://github.com/dzenbot/DZNEmptyDataSet
提示：主要用于UITableView和UICollectionView，也可以用于UIScrollView，其实主要是前两个会用到空白或者网络出错页，采用给UIScrollView添加代理方法来给页面添加空白页面，源码很有学习意义。
首先导入工程：
pod 'DZNEmptyDataSet'
或手动导入，下载文件，将Source文件下下的文件拖入工程

#import "UIScrollView+EmptyDataSet.h"

初始化
引入代理

<DZNEmptyDataSetSource, DZNEmptyDataSetDelegate>
让tableview遵守代理
  self.tableView.emptyDataSetSource = self;
  self.tableView.emptyDataSetDelegate = self;

//这行代码必须加上，可以去除tableView的多余的线，否则会影响美观
  self.tableView.tableFooterView = [UIView new];

常用代理方法
1.返回图片

 - (UIImage *)imageForEmptyDataSet:(UIScrollView *)scrollView {
    return [UIImage imageNamed:@"empty_placeholder"];
    }

2.返回标题文本

- (NSAttributedString *)titleForEmptyDataSet:(UIScrollView *)scrollView
{
    NSString *text = @"Please Allow Photo Access";
    NSDictionary *attributes = @{NSFontAttributeName: [UIFont boldSystemFontOfSize:18.0f], NSForegroundColorAttributeName: [UIColor darkGrayColor]};
    return [[NSAttributedString alloc] initWithString:text attributes:attributes];
}

3.返回详细描述

- (NSAttributedString *)descriptionForEmptyDataSet:(UIScrollView *)scrollView {
    NSString *text = @"This allows you to share photos from your library and save photos to your camera roll.";

    NSMutableParagraphStyle *paragraph = [NSMutableParagraphStyle new];
    paragraph.lineBreakMode = NSLineBreakByWordWrapping;
    paragraph.alignment = NSTextAlignmentCenter;

    NSDictionary *attributes = @{NSFontAttributeName: [UIFont systemFontOfSize:14.0f],
                                 NSForegroundColorAttributeName: [UIColor lightGrayColor],
                                 NSParagraphStyleAttributeName: paragraph};

    return [[NSAttributedString alloc] initWithString:text attributes:attributes];                      
    }

4.按钮文本或者背景样式

  - (NSAttributedString *)buttonTitleForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state {
    NSDictionary *attributes = @{NSFontAttributeName: [UIFont boldSystemFontOfSize:17.0f]};

    return [[NSAttributedString alloc] initWithString:@"Continue" attributes:attributes];
    }
    
    - (UIImage *)buttonImageForEmptyDataSet:(UIScrollView *)scrollView forState:(UIControlState)state {
    return [UIImage imageNamed:@"button_image"];
    }

5.空白页的背景色

 - (UIColor *)backgroundColorForEmptyDataSet:(UIScrollView *)scrollView {
    return [UIColor whiteColor];
    }

6.也可以自定义

    - (UIView *)customViewForEmptyDataSet:(UIScrollView *)scrollView {
    //加入你自定义的view
    UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    [activityView startAnimating];
    return activityView;
    }

7.其他需求

 //是否显示空白页，默认YES
    - (BOOL)emptyDataSetShouldDisplay:(UIScrollView *)scrollView {
    return YES;
    }
    
    //是否允许点击，默认YES
    - (BOOL)emptyDataSetShouldAllowTouch:(UIScrollView *)scrollView {
    return YES;
    }
    
    //是否允许滚动，默认NO
    - (BOOL)emptyDataSetShouldAllowScroll:(UIScrollView *)scrollView {
    return YES;
    }
    
    //图片是否要动画效果，默认NO
    - (BOOL) emptyDataSetShouldAllowImageViewAnimate:(UIScrollView *)scrollView {
    return YES;
    }
    
    //空白页点击事件
    - (void)emptyDataSetDidTapView:(UIScrollView *)scrollView {
    
    }
    
    //空白页按钮点击事件
    - (void)emptyDataSetDidTapButton:(UIScrollView *)scrollView {
   
    }