Question

因此，人们对此特定事件的大多数问题是在发生动画时scrollViewDidScroll触发。我的情况正好相反。我认为scrollViewDidScroll不应该在我的案件中解雇。

让我进一步解释。

我正在使用scrollViewDidScroll中的动画，这一直很有效，直到我将UITableView移动到UIView类中。

- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
   // Animation code here.
   NSLog(@"scrollViewDidScroll");
}

- (void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
   NSLog(@"scrollViewDidEndDecelerating");
   NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
   [_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
}

这提供了一种平滑的滚动体验，可以快速回到上一个表格行。由于scrollViewDidScroll，控制台可以验证scrollToRowAtIndexPath事件是否正在触发。

控制台：

2014-03-31 22:21:43.346 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.379 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.429 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.462 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.479 Project[45843:a0b] scrollViewDidEndDecelerating
2014-03-31 22:21:43.496 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.513 Project[45843:a0b] scrollViewDidScroll
2014-03-31 22:21:43.529 Project[45843:a0b] scrollViewDidScroll

问题：

1。如何确保事件scrollViewDidScroll仅在用户交互时触发，而不是代码自动化？

2。是否有其他方法提供与scrollToRowAtIndexPath相同的功能而不触发scrollViewDidScroll？

Answer 1

I know this is a very old question. I just have been in a similar situation that I need to run some code only when the user is scrolling but not when I call scrollToRowAtIndexPath. I have found an easier solution for this using the scrollView variables dragging and decelerating.

we have 3 cases of scrolling here.

user is dragging
user just ended dragging and the tableview is decelrating
programmatically called scrollForRowAtIndexPath:

All of the cases above will trigger scrollViewDidScroll: but

user is dragging dragging is True and decelerating is False
user just ended dragging and the tableview is decelrating dragging is False and decelerating is True
programmatically called scrollForRowAtIndexPath: dragging is False and decelerating is False

So your code will be like something like this:

- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
    if (scrollView.dragging)
     {
       // Do what you want when user is dragging
     } else if (scrollView.decelerating) 
     {
       // Do what you want when table is decelerating after finished dragging
     } else 
     {
       // Do what you want when table is scrolling programmatically.
     }
}

Or if you want to just distinguish the scrolling progammatically

- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
    if (scrollView.dragging || scrollView.decelerating)
     {
       // Scrolling by the user
     } else 
     {
       // Scrolling by the code
     }
}

Answer 2

我发布问题后不久，我休息了一会儿，回过头来看问题并弄清楚了。应该尽快完成，而不是浪费几个小时。的Bleh！

解决方案很简单，设置一个bool标志，在任何编程滚动之前设置，然后在使用事件scrollViewDidEndScrollingAnimation完成动画后更改。

bool performingAutomatedScroll = false;

- (void) scrollViewDidScroll:(UIScrollView *)scrollView {

  // If we are scrolling because of code, don't use any animations.
  if (performingAutomatedScroll) return;

  // Animation code here.
}

- (void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView {

  performingAutomatedScroll = true;
  NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
  [_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
  [_myTableView reloadRowsAtIndexPaths:[_timeCarousel indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationNone];

}

- (void) scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {

  if (!decelerate) {
    performingAutomatedScroll = true;
    NSArray *indexPaths = [_myTableView indexPathsForVisibleRows];
    [_myTableView scrollToRowAtIndexPath:[indexPaths objectAtIndex:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
    [_myTableView reloadRowsAtIndexPaths:[_timeCarousel indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationNone];
  }

}

-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
  performingAutomatedScroll = false;
}

UITableView scrollViewDidScroll在动画上触发

2 个答案: