floor-round-ceil

英文意思：floor：地板 round:变圆 ceil:天花板
因为项目里面 6p计算scrollView分页和滑动到顶部出现误差所以这里需要重新审视一下这些系统函数

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    NSInteger index = scrollView.contentOffset.x / self.contentBG.width;
    NSLog(@"scrollView.contentOffset.x:%f,self.contentBG.width:%f,%ld",scrollView.contentOffset.x,self.contentBG.width,index);
    CGFloat tmpOffsetX = scrollView.contentOffset.x / self.contentBG.width;
    NSLog(@"%f",tmpOffsetX);
    index = floor(tmpOffsetX);
    NSLog(@"index:%ld,floor(tmpOffsetX):%f",index,floor(tmpOffsetX));
    index = round(tmpOffsetX);
    NSLog(@"index:%ld,round(tmpOffsetX):%f",index,round(tmpOffsetX));
    index = ceil(tmpOffsetX);
    NSLog(@"index:%ld,ceil(tmpOffsetX):%f",index,ceil(tmpOffsetX));
    if (1 == 1.000000) {
        NSLog(@"6个0");
    }
    if (1 == 1.00) {
        NSLog(@"2个0");
    }
}

scrollView.contentOffset.x:376.333333,self.contentBG.width:376.464000,0
0.999653
index:0,floor(tmpOffsetX):0.000000
index:1,round(tmpOffsetX):1.000000
index:1,ceil(tmpOffsetX):1.000000
6个0
2个0

***以上出现误差这时候分页索引应该用四舍五入round来取 *