I'm experiencing a major delay with my FlatList component with a header when I introduced RN 0.45, and I think it may be a bug or performance regression. I have about ~110 items in the list. I created an expo snack to easily show what is happening:

https://snack.expo.io/rJwjIi6Sb

Line 53 is commented out.

If you load the app in iOS simulator or on an iPhone using Expo's QR code, you'll be able to immediately press on a list item and get an alert.

If you uncomment line 53 to add the search bar back to the header, and you should experience a pretty significant delay on first load (I count about 2-3 seconds on my iPhone 6) before the alert will fire off.

It seems that you can put literally anything in the header to cause this to happen. This doesn't happen in my 0.44 RN app (Expo SDK v17) using the same code.

If anyone has trouble reproducing this or you aren't getting the same experience described above, let me know. And if for some reason I'm doing something wrong that may be causing this, I'm all ears.