下拉刷新

    // 1.添加下拉刷新控件
    UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
    [self.tableView addSubview:refreshControl];
    
    // 2.监听状态
    [refreshControl addTarget:self action:@selector(refreshControlStateChange:) forControlEvents:UIControlEventValueChanged];
    
    // 3.让刷新控件自动进入刷新状态
    [refreshControl beginRefreshing];
    
    // 4.加载数据
    [self refreshControlStateChange:refreshControl];

- (void)refreshControlStateChange:(UIRefreshControl *)refreshControl
{
        [refreshControl endRefreshing];
}
/**
 *  提示用户最新的微博数量
 *
 *  @param count 最新的微博数量
 */
- (void)showNewStatusesCount:(int)count
{
    // 1.创建一个UILabel
    UILabel *label = [[UILabel alloc] init];
    
    // 2.显示文字
    if (count) {
        label.text = [NSString stringWithFormat:@"共有%d条新的微博数据", count];
    } else {
        label.text = @"没有最新的微博数据";
    }
    
    // 3.设置背景
    label.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageWithName:@"timeline_new_status_background"]];
    label.textAlignment = NSTextAlignmentCenter;
    label.textColor = [UIColor whiteColor];
    
    // 4.设置frame
    label.width = self.view.width;
    label.height = 35;
    label.x = 0;
    label.y = 64 - label.height;
    
    // 5.添加到导航控制器的view
//    [self.navigationController.view addSubview:label];
    [self.navigationController.view insertSubview:label belowSubview:self.navigationController.navigationBar];
    
    // 6.动画
    CGFloat duration = 0.75;
//    label.alpha = 0.0;
    [UIView animateWithDuration:duration animations:^{
        // 往下移动一个label的高度
        label.transform = CGAffineTransformMakeTranslation(0, label.height);
//        label.alpha = 1.0;
    } completion:^(BOOL finished) { // 向下移动完毕
        
        // 延迟delay秒后，再执行动画
        CGFloat delay = 1.0;
        
        [UIView animateWithDuration:duration delay:delay options:UIViewAnimationOptionCurveEaseInOut animations:^{
            
            // 恢复到原来的位置
            label.transform = CGAffineTransformIdentity;
//            label.alpha = 0.0;
            
        } completion:^(BOOL finished) {
            
            // 删除控件
            [label removeFromSuperview];
        }];
    }];
}
/**
 UIViewAnimationOptionCurveEaseInOut            = 0 << 16, // 开始：由慢到快，结束：由快到慢
 UIViewAnimationOptionCurveEaseIn               = 1 << 16, // 由慢到块
 UIViewAnimationOptionCurveEaseOut              = 2 << 16, // 由快到慢
 UIViewAnimationOptionCurveLinear               = 3 << 16, // 线性，匀速
 */