iOS UITableView 无数据占位视图

新建扩展UITableView的Category 名为 LyEmptyData

.h

//如果出现个别页面无背景图情况，可以手动调用该方法,否则无需调用
-(void)loadBackground;

.m

+(void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        @autoreleasepool {
            [self swizzleMethod:@selector(reloadData) withMethod:@selector(ly_reloadData) error:nil];
        };
    });
}
#pragma mark - 替换系统方法
-(void)ly_reloadData{
    [self ly_reloadData];
    [self loadBackground];
}
#pragma mark - 实现自定义背景判断
-(void)loadBackground{
   if (![self isMemberOfClass:[UITableView class]]) {
        self.backgroundView = nil;
        return;
    }
    if (self.visibleCells.count <= 0 && self.numberOfSections <= 1) {
        if (self.tableHeaderView == nil && self.tableFooterView == nil) {
            NSLog(@"%ld",(long)self.numberOfSections);
            // 没有数据的时候，UILabel的显示样式
            UITableViewBackgroundView * messageBackgroundView = [UITableViewBackgroundView new];
            self.backgroundView = messageBackgroundView;
            self.separatorStyle = UITableViewCellSeparatorStyleNone;
        }
    } else {
        self.backgroundView = nil;
    }
}

#pragma mark - 设置系统交换
+ (BOOL)swizzleMethod:(SEL)originalSelector withMethod:(SEL)swizzledSelector error:(NSError **)error
{
    Method originalMethod = class_getInstanceMethod(self, originalSelector);
    if (!originalMethod) {
        NSString *string = [NSString stringWithFormat:@" %@ 类没有找到 %@ 方法",NSStringFromClass([self class]),NSStringFromSelector(originalSelector)];
        *error = [NSError errorWithDomain:@"NSCocoaErrorDomain" code:-1 userInfo:[NSDictionary dictionaryWithObject:string forKey:NSLocalizedDescriptionKey]];
        return NO;
    }
    Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector);
    
    if (!swizzledMethod) {
        NSString *string = [NSString stringWithFormat:@" %@ 类没有找到 %@ 方法",NSStringFromClass([self class]),NSStringFromSelector(swizzledSelector)];
        *error = [NSError errorWithDomain:@"NSCocoaErrorDomain" code:-1 userInfo:[NSDictionary dictionaryWithObject:string forKey:NSLocalizedDescriptionKey]];
        return NO;
    }
    
    if (class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod)))
    {
        class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
    } else {
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
    return YES;
}