Our app records data for filling out reports. After continuously entering data, the appearance and disappearance of the software keyboard slows down considerably, making the app unusable.
This occurs when the ipa file is built with Xcode 6 (SDK 8.3). If we build the ipa file with the same code in Xcode 5 (SDK 7.1), the problem does not occur.
When app is experiencing the performance issues, they immediately go away if we connect a hardware keyboard through bluetooth, and come back when we disconnect the keyboard. This is how we determined that it was the actual keyboard and not just when the text field receives focus.
The issue occurs whether we are using the default iOS keyboard or a third party keyboard.
This issue is occurring in the version of the app that is currently available in the app store, so it wasn't rejected by the app reviewers.
We have profiled the code using Time instrument. We see _CfxNotificationPost growing. The response to keyboard events start at 17ms, 120ms, 300ms, 900ms for every incremental test. We have looked at memory leaks and eliminated memory leaks.
As far as code, the problem occurs throughout the app, but an example of somewhere that we see the issue is here:
[self.siteLocationTextField resignFirstResponder]
It also happens if the user manually closes the keyboard by tapping the button on the keyboard to dismiss it.