tableview 一键按钮button返回顶部

{
 CGFloat oldContenoffsetY, newContenoffsetY;
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    oldContenoffsetY = scrollView.contentOffset.y;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    newContenoffsetY = scrollView.contentOffset.y;
    CGFloat deltaY = oldContenoffsetY - newContenoffsetY;
    if (deltaY > 0)
    {
        self.upToTopBtn.hidden = NO;
    }else
    {
        self.upToTopBtn.hidden = YES;
    }
}

-(UIButton *)upToTopBtn
{
    if (!_upToTopBtn)
    {
        _upToTopBtn = [UIButton buttonWithType:UIButtonTypeSystem];
        _upToTopBtn.frame = CGRectMake(IPHONE_W-60, IPHONE_H-150, 40, 40);
//        _upToTopBtn.backgroundColor=[UIColor redColor];
        [_upToTopBtn setBackgroundImage:[UIImage imageNamed:@"一键置顶.png"] forState:UIControlStateNormal];
        [_upToTopBtn addTarget:self action:@selector(upToTopBtnAction) forControlEvents:UIControlEventTouchUpInside];
        _upToTopBtn.hidden = YES;
    }
    return _upToTopBtn;
}
-(void)upToTopBtnAction
{
    //
    self.listCollectV.contentOffset = CGPointMake(0, 0);
    self.upToTopBtn.hidden = YES;
}