`measure` or `onLayout` returns `0` on android if view is in `Modal`

[buschco]

Description

onLayout and useLayoutEffect with measure gives me wrong values if View is in a Modal, but is correct on iOS.

Steps to reproduce

1. measure a View inside and outside of a Modal with measure or onLayout
2. See difference between iOS and android at the View inside the Modal

React Native Version

0.79.4

Affected Platforms

Runtime - Android

Output of npx @react-native-community/cli info

info Fetching system and libraries information...
System:
  OS: macOS 15.5
  CPU: (14) arm64 Apple M4 Pro
  Memory: 213.98 MB / 48.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 18.20.5
    path: ~/.nvm/versions/node/v18.20.5/bin/node
  Yarn:
    version: 1.22.22
    path: ~/.nvm/versions/node/v18.20.5/bin/yarn
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v18.20.5/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/colin/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23339.11.2421.12550806
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.15
    path: /Users/colin/.sdkman/candidates/java/current/bin/javac
  Ruby:
    version: 3.3.6
    path: /Users/colin/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.0
    wanted: 18.0.0
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.4
    wanted: 0.79.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: true

info React Native v0.80.1 is now available (your project is running on v0.79.4).
info Changelog: https://github.com/facebook/react-native/releases/tag/v0.80.1
info Diff: https://react-native-community.github.io/upgrade-helper/?from=0.79.4&to=0.80.1
info For more info, check out "https://reactnative.dev/docs/upgrading?os=macos".

Stacktrace or Logs

Connection established to app='com.reproducerapp' on device='sdk_gphone_arm64 - 11 - API 30'.

MANDATORY Reproducer

https://github.com/buschco/react-native-flow/tree/measure-in-modal

Screenshots and Videos

Screen.Recording.2025-07-05.at.10.59.33.mov

[buschco]

Just tested react-native@0.80.1 with the same results https://github.com/buschco/react-native-repro-80

[buschco]

A possible workaround: Introduce a second visible state that is set to true by the Modals onShow callback:

  const [visible, setVisible] = useState(false);
  const [visibleFr, setVisibleFr] = useState(false);

  return (
    <>
      <Modal
        visible={visible}
        onShow={() => setVisibleFr(true)}
      >
          {visibleFr && <Content />} // <- layout calculations will now work on android