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

Call this method to reload all the data that is used to construct the table, including cells, section headers and footers, index arrays, and so on. For efficiency, the table view redisplays only those rows that are visible. It adjusts offsets if the table shrinks as a result of the reload. The table view's delegate or data source calls this method when it wants the table view to completely reload its data. It should not be called in the methods that insert or delete rows, especially within an animation block implemented with calls to beginUpdates and endUpdates

According to apples documentation, reloadData only reloads visible cells. This could be a problem if you are not using cell identifiers properly.

This still could be a threading issue. Check to see if you're running on the main thread before calling reloadData, and if you're not, run a dispatch_sync on the main queue.

If you try to run dispatch_anything on the main queue when you're already on the main queue the app will quit.