本文轉自：http://blog.csdn.net/jiajiayouba/article/details/23887551
**1. contentSize: **The size of the content view. 其實就是scrollview可以滾動的區(qū)域肠牲，比如frame = (0 ,0 ,320 ,480) contentSize = (320 ,960)幼衰，代表你的scrollview可以上下滾動，滾動區(qū)域為frame大小的兩倍缀雳。
2.contentOffset:The point at which the origin of the content view is offset from the origin of the scroll view. 是scrollview當前顯示區(qū)域頂點相對于frame頂點的偏移量渡嚣，比如上個例子你拉到最下面，contentoffset就是(0 ,480)肥印，也就是y偏移了480
3. contentInset:The distance that the content view is inset from the enclosing scroll view.是scrollview的contentview的頂點相對于scrollview的位置识椰，例如你的contentInset = (0 ,100)，那么你的contentview就是從scrollview的(0 ,100)開始顯示
/* 上拉刷新一般實現(xiàn)代碼如下 */
//上拉加載更多
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
[_refreshHeaderView egoRefreshScrollViewDidEndDragging:scrollView];
float offset=scrollView.contentOffset.y;
float contentHeight=scrollView.contentSize.height;
float sub=contentHeight-offset;
if ((scrollView.height-sub)>20) {//如果上拉距離超過20p深碱，則加載更多數(shù)據(jù)
//[self loadMoreData];//此處在view底部加載更多數(shù)據(jù)
}
}
