用于UITableView的NSFetchedResultsController在插入更改时滚动到顶部

Question

我有一个UITableView，它由NSFetchedResultsController备份。我想滚动到的tableView的隐藏行作为被插入表后的搜索栏上方，即

-> row created 
-> row inserted 
-> row insert animation finished 
-> **scroll to top hiding search controller** 

知道如果行已交锋的唯一方法是看NSFetchedResultsControllerDelegate API controller:didChangeObject:atIndexPath:forChangeType:newIndexPath。

Answer 1

我会使用CATransaction得到通知时UITableView成品动画：

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller { 
    [CATransaction begin]; 
    [CATransaction setCompletionBlock:^{ 
     if(self.shouldScrollToTop) { 
      [self.tableView setContentOffset:CGPointZero animated:YES]; 
     } 
     self.shouldScrollToTop = NO; 
    }]; 

    [self.tableView beginUpdates]; 
} 

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { 
    [self.tableView endUpdates]; 

    [CATransaction commit]; 
} 

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { 
    switch(type) { 
     case NSFetchedResultsChangeInsert: 
      [self.tableView insertRowsAtIndexPaths:@[ newIndexPath ] withRowAnimation:UITableViewRowAnimationAutomatic]; 

      self.shouldScrollToTop = YES; 
      break; 
    } 
}