有時候項目中有這樣的需求，頁面包含一個UITableVeiw，當沒有數據的時候顯示一張占位圖片，點擊圖片可以重新刷新數據。效果圖如下：

有數據時.png

沒數據時.png

思路

為UITableView增加個Category，利用方法method_exchangeImplementations交換reloadData方法為real_ReloadData，在real_ReloadData方法內判斷是否有數據源，再動態顯示占位的UIView。

在創建UITableView的地方一句代碼設置占位控件。

    tableView.placeHolderView = [[PlaceholderView alloc]initWithFrame:tableView.bounds onTapView:^{
      //點擊占位圖片
    }];
    [self.view addSubview:tableView];

UITableView+Placeholder.h文件

#import <UIKit/UIKit.h>
@interface UITableView (Placeholder)
/* 占位圖 */
@property (nonatomic, strong) UIView *placeHolderView;
@end

UITableView+Placeholder.m文件

#import "UITableView+Placeholder.h"
#import <objc/runtime.h>

@implementation UITableView (Placeholder)

+ (void)load
{
    //交換刷新方法
    Method reloadData =class_getInstanceMethod(self,  @selector(reloadData));
    Method real_ReloadData =class_getInstanceMethod(self, @selector(real_ReloadData));
    method_exchangeImplementations(reloadData, real_ReloadData);
}

-(void)real_ReloadData
{
    [self dataIsEmpty];
    [self real_ReloadData];
}

/** 判斷是否有數據源，沒有數據源則顯示占位圖片  */
- (void)dataIsEmpty
{
    BOOL isEmpty = YES;
    id<UITableViewDataSource> dataSourse = self.dataSource;
    //檢測是否有數據源
    if ([dataSourse respondsToSelector:@selector(numberOfSectionsInTableView:)]) {//group
        NSInteger sections = [dataSourse numberOfSectionsInTableView:self];
        if (sections >0) {
            isEmpty = NO;
        }
    }else if([dataSourse respondsToSelector:@selector(tableView:numberOfRowsInSection:)]){//plain
        NSInteger rows = [dataSourse tableView:self numberOfRowsInSection:0];
        if (rows >0) {
            isEmpty = NO;
        }
    }
    if (isEmpty) {//顯示占位圖
        [self.placeHolderView removeFromSuperview];
        [self addSubview:self.placeHolderView];
    }else{//移除占位圖片
        [self.placeHolderView removeFromSuperview];
    }
}
- (void)setPlaceHolderView:(UIView *)placeHolderView
{
    objc_setAssociatedObject(self, @selector(placeHolderView), placeHolderView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIView *)placeHolderView
{
    return objc_getAssociatedObject(self, @selector(placeHolderView));
}

自定義占位的UIView 為PlaceholderView

PlaceholderView.h文件

#import <UIKit/UIKit.h>
//點擊后的回調
typedef void(^TapBlock)();
@interface PlaceholderView : UIView
@property(nonatomic,copy)TapBlock onTapBlock;
- (instancetype)initWithFrame:(CGRect)frame onTapView:(TapBlock)onTapBlock;
@end

PlaceholderView.m文件

#import "PlaceholderView.h"

@implementation PlaceholderView
{
    UIImageView *_imageView;
}

- (instancetype)initWithFrame:(CGRect)frame onTapView:(TapBlock)onTapBlock
{
    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor whiteColor];
        self.onTapBlock = onTapBlock;
        [self setupSubViews];
    }
    return self;
}
-(void)setupSubViews
{
    UIImageView *imageView =[[UIImageView alloc]init];
    imageView.userInteractionEnabled = YES;
    imageView.contentMode = UIViewContentModeCenter;
    [imageView setImage:[UIImage imageNamed:@"nodataPlaceholder"]];
    _imageView = imageView;
    [self addSubview:imageView];
    
    [self addGestureRecognizer:[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(onTapView:)]];
}
-(void)layoutSubviews
{
    [super layoutSubviews];
    _imageView.frame = self.bounds;
}
/** 增加點擊手勢 **/
-(void)onTapView:(UITapGestureRecognizer *)recognizer
{
    if (self.onTapBlock) {
        self.onTapBlock();
    }
}

這樣當這個需求發生變化時，改動相對來說更小。當然，還可以把設置placeholderView的代碼也封裝到UItableView分類的init里面去。
點擊下載Demo 有什么錯誤歡迎批評指正 。