IOS开发 UITableView empty 简单实用

android开发的时候，ListView 的empty处理得心应手，以为iOS开发 UITableView 处理empty 同样简单，事实证明，有了GitHub上的这篇文章，证明我的想法很是没错的。

Github地址：https://github.com/dzenbot/DZNEmptyDataSet

Github对这个功能有点喝集成已经说的很清楚了

我做个简单翻译

2，优点

Empty Data Sets are helpful for:

• Avoiding white-screens and communicating to your users why the screen is empty.
• 避免tableview没数据的时候只显示白屏，用户会感激茫然
• Calling to action (particularly as an onboarding process).
• 可以提高操作、交互性
• Avoiding other interruptive mechanisms like showing error alerts.
• 避免tableview没数据的时候用alert这一类的提示强行打断用户的操作
• Beeing consistent and improving the user experience.
• 一致、连贯行好，并且提升用户体验
• Delivering a brand presence.
• 可以更好的展现出你的品牌

2，先看效果在决定用不用

3，集成

visit CocoaPods' auto-generated doc

http://cocoadocs.org/docsets/DZNEmptyDataSet/1.6.1

1，从下载的demo中拷贝这两个原文件到你的项目里

UIScrollView+EmptyDataSet.h

UIScrollView+EmptyDataSet.m

2，需要显示empty的table做如下处理

@interface MainViewController : UITableViewController <DZNEmptyDataSetSource, DZNEmptyDataSetDelegate>- (void)viewDidLoad{    [super viewDidLoad];    self.tableView.emptyDataSetSource = self;    self.tableView.emptyDataSetDelegate = self;    // A little trick for removing the cell separators    self.tableView.tableFooterView = [UIView new];}

好累，不翻译了

Data Source Implementation

Return the content you want to show on the empty state, and take advantage of NSAttributedString features to customise the text appearance.

The image for the empty state:

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

The attributed string for the title of the empty state:

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

The attributed string for the description of the empty state:

- (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:14.0],                                 NSForegroundColorAttributeName: [UIColor lightGrayColor],                                 NSParagraphStyleAttributeName: paragraph};    return [[NSAttributedString alloc] initWithString:text attributes:attributes];                      }

The attributed string to be used for the specified button state:

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

or the image to be used for the specified button state:

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

The background color for the empty state:

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

If you need a more complex layout, you can return a custom view instead:

- (UIView *)customViewForEmptyDataSet:(UIScrollView *)scrollView{    UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];    [activityView startAnimating];    return activityView;}

Additionally, you can modify the horizontal and/or vertical alignments (as when using a tableHeaderView):

- (CGPoint)offsetForEmptyDataSet:(UIScrollView *)scrollView{    return CGPointMake(0, -self.tableView.tableHeaderView.frame.size.height/2);}

Delegate Implementation

Return the behaviours you would expect from the empty states, and receive the user events.

Asks to know if the empty state should be rendered and displayed (Default is YES) :

- (BOOL)emptyDataSetShouldDisplay:(UIScrollView *)scrollView{    return YES;}

Asks for interaction permission (Default is YES) :

- (BOOL)emptyDataSetShouldAllowTouch:(UIScrollView *)scrollView{    return YES;}

Asks for scrolling permission (Default is NO) :

- (BOOL)emptyDataSetShouldAllowScroll:(UIScrollView *)scrollView{    return YES;}

Notifies when the dataset view was tapped:

- (void)emptyDataSetDidTapView:(UIScrollView *)scrollView{    // Do something}

Notifies when the data set call to action button was tapped:

- (void)emptyDataSetDidTapButton:(UIScrollView *)scrollView{    // Do something}

Refresh layout

If you need to refresh the empty state layout, simply call:

[self.tableView reloadData];

or

[self.collectionView reloadData];

depending of which you are using.

Force layout update

You can also call [self.tableView reloadEmptyDataSet] to invalidate the current empty state layout and trigger a layout update, bypassing -reloadData. This might be useful if you have a lot of logic on your data source that you want to avoid calling, when not needed. [self.tableView reloadEmptyDataSet] is the only way to refresh content when using with UIScrollView.