一、每次拖动都会调用的方法是
先调用一次
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
接着调用多次
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
最后拖动结束的时候调用
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
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二、每次拖动只有拖动很快才会调用的方法是
-
(void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
-
(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
总结：这两个方法不一定每次都会调用，还有需要注意调用的顺序
三、调用的顺序
快速滚动的例子：
2021-10-15 17:51:05.729940+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewWillBeginDragging=0.000000
2021-10-15 17:51:05.730912+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:51:05.755938+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:51:05.816167+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:51:05.867274+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:51:05.867910+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewWillEndDragging=0.000000
2021-10-15 17:51:05.868098+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidEndDragging=0.000000
2021-10-15 17:51:05.868300+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewWillBeginDecelerating=0.000000
2021-10-15 17:51:05.915003+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:51:05.976232+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
scrollViewDidEndDecelerating**=0.000000**
2021-10-15 17:51:08.601726+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidEndDecelerating=0.000000
****\
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慢速滚动的例子：
2021-10-15 17:55:43.454379+0800 dfcft-iphone-free[13773:215065] **发发发****scrollViewWillBeginDragging=**0.000000
2021-10-15 17:55:43.455001+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:55:43.485702+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewDidScroll=0.000000
2021-10-15 17:55:43.556315+0800 dfcft-iphone-free[13773:215065] **发发发****scrollViewDidScroll=**0.000000
2021-10-15 17:55:44.857680+0800 dfcft-iphone-free[13773:215065] 发发发scrollViewWillEndDragging=0.000000
2021-10-15 17:55:44.860091+0800 dfcft-iphone-free[13773:215065] **发发发****scrollViewDidEndDragging=**0.000000
****\
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