cellForRowAtIndexPath：被立即调用，而numberOfRowsInSection：不被调用

Question

I've encountered this issue a few times after the reloadData method on a UITableView is invoked, and I haven't figured out why?

This is a problem because if the data of table view is updated, the tableview will unnecessarily query the cell on a non-existent row. It is non-existent, because the numberOfRowsInSection: somehow is not called before this is happening.

Is it affected by how the reloadData method is being invoked? (It is invoked on the main thread, not anywhere else).

Update:

cellForRowAtIndexPath: could be invoked by other means such as querying visibleCells. It may be the case that this isn't part of reloadData.

Answer 1

调用此方法以重新加载用于构造表的所有数据，包括单元格，节的页眉和页脚，索引数组等。 为了提高效率，表视图仅重新显示那些可见的行。 如果表由于重新加载而缩小，则会调整偏移量。 当表视图的委托或数据源希望表视图完全重新加载其数据时，将调用此方法。 不应在插入或删除行的方法中调用它，尤其是在通过调用beginUpdates和endUpdates实现的动画块中

根据apples文档，reloadData仅重新加载可见的单元格。 如果您没有正确使用单元格标识符，则可能会出现问题。

这仍然可能是线程问题。 在调用reloadData之前，检查是否在主线程上运行，如果不是，请在主队列上运行dispatch_sync。

如果您已经在主队列中时尝试在主队列上运行dispatch_anything，则该应用程序将退出。