on keyboard dismiss react native code example
Example: keyboard close when typing react native
It's because the ListHeaderComponent from the FlatList is being re-render each time you change the state. I'm not sure to see a quick solution to fix in this context of usage.
Even though if you have the possibility to use HeaderComponent instead I would recommend you do that: https://snack.expo.io/@jeremdsgn/modalize-issue
I'm closing this issue