[Android] Content doesn't resize when tab bar visibility changes (tabBarHidden)

[JJalit]

Before submitting a new issue

• I tested using the latest version of the library, as the bug might be already fixed.
• I tested using a supported version of react native.
• I checked for possible duplicate issues, with possible answers.

Bug summary

On Android, when tabBarHidden is toggled to true, the native bottom navigation view is set to GONE and its space is reclaimed at the native level, but the React content does not grow to fill it. The screen keeps its old height, leaving a blank strip at the bottom exactly the height of the tab bar. Bottom-anchored elements (position: 'absolute', bottom: 0) end up floating ~80dp above the actual bottom of the screen. Toggling back to visible has the same problem in reverse until something else triggers a relayout.

I tracked it down to the layout listener in RCTTabView.kt. The size-change guard compares the bounds of the whole container (ReactBottomNavigationView), but when only the tab bar visibility changes, the container keeps the exact same size — only the inner layoutHolder grows or shrinks:

post {
  addOnLayoutChangeListener { _, left, top, right, bottom, _, _, _, _ ->
    val newWidth = right - left      // container size — unchanged when tab bar is hidden
    val newHeight = bottom - top

    onTabBarMeasuredListener?.invoke(...)

    if (newWidth != lastReportedSize?.width || newHeight != lastReportedSize?.height) {
      // never reached in this case, so onNativeLayoutListener doesn't fire
      onNativeLayoutListener?.invoke(dpWidth, dpHeight)
      lastReportedSize = Size(newWidth, newHeight)
    }
  }
}

Two problems compound here:

1. The guard compares the container size, while the value actually reported to JS is the layoutHolder size. When the tab bar is hidden, the container stays the same but layoutHolder changes, so the guard filters the update out.
2. The listener is attached to the container, and OnLayoutChangeListener only fires when that view's own bounds change — which they don't in this scenario. So even the callback itself may not run.

As a result onNativeLayout never reaches the JS side, setMeasuredDimensions keeps the stale height, and the children rendered by TabView stay at the old size.

Verified on an emulator with uiautomator dump: after hiding the tab bar, the native layoutHolder grows to full screen height (2400px on my device), while the React subtree inside it stays at the previous 2126px.

iOS is not affected.

Library version

1.4.0

Environment info

System:
  OS: macOS 26.5.2
  CPU: (18) arm64 Apple M5 Pro
Binaries:
  Node: 24.13.0
  Yarn: 3.6.4
  npm: 11.6.2
npmPackages:
  react: 19.2.3
  react-native: 0.86.0
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Steps to reproduce

1. Android app using createNativeBottomTabNavigator (New Architecture).
2. Render a screen with a bottom-anchored view, e.g. an action bar with position: 'absolute', bottom: 0.
3. Toggle tabBarHidden to true (typical case: entering a selection/edit mode).
4. The tab bar disappears, but the bottom-anchored view stays where the tab bar's top edge used to be, with an empty strip below it.

Tested on an Android 16 emulator (arm64), RN 0.86, and reproduced consistently.

Reproducible sample code

const [hidden, setHidden] = useState(false);

<TabView tabBarHidden={hidden} ...>
  {/* screen content */}
  <View style={{ position: 'absolute', bottom: 0, left: 0, right: 0, height: 56 }}>
    <Button title="toggle" onPress={() => setHidden(v => !v)} />
  </View>
</TabView>

I have a fix working locally (report the layoutHolder size instead, and also listen to layoutHolder layout changes so the visibility-toggle case is caught). Will open a PR.