VirtualizedList- inefficient function passing for CellRenderer

• Review the documentation
• Search for existing issues
• Use the latest React Native release - using version 0.55.2 did not see any changes to the FlatListComponent since that version.

Environment

Run react-native info in your terminal and paste its contents here.

Environment:
  OS: Windows 10
  Node: 8.11.1
  Yarn: 0.21.3
  npm: 5.8.0
  Watchman: Not Found
  Xcode: N/A
  Android Studio: Version  3.0.0.0 AI-171.4408382

Packages: (wanted => installed)
  react: 16.3.1 => 16.3.1
  react-native: ^0.55.2 => 0.55.4

Description

I used the npm package why-did-you-update to help optimize my components and prevent re-renders. However there is a re-render that I cannot control. This happens for every item in the list. My gues

CellRenderer.props: Changes are in functions only. Possibly avoidable re-render?
Functions before: {onLayout: ƒ}
Functions after: {onLayout: ƒ}

It seems this is caused by an anonymous function at https://github.com/facebook/react-native/blob/d756d94b3a7e2812f17f549c57767ac63734b49c/Libraries/Lists/VirtualizedList.js#L691

I propose that this function be defined on the class to prevent unnecessary re-renders.

Il callback segnalato si trova in Libraries/Lists/VirtualizedList.js, alla riga collegata. Inizia da lì e usa why-did-you-update con il caso descritto di FlatList e CellRenderer per verificare se il rerendering causato solo dalla funzione è evitabile. Il lavoro è completato quando il callback non causa più questi rerendering non necessari di CellRenderer senza modificare il comportamento della lista.