feat(android): prevent native tab selection in TabsContainer

When a tab has preventNativeSelection enabled, block native user taps
from selecting it. Returns false from OnItemSelectedListener to prevent
BottomNavigationView from updating its visual selection state, and emits
onTabSelectionPrevented event to JS via TabsContainerDelegate chain.

Author: kkafar

android/src/main/java/com/swmansion/rnscreens/gamma/tabs/container/TabsContainer.kt

@@ -361,6 +361,12 @@ internal class TabsContainer(
 
         val isRepeated = nextSelectedFragment === currSelectedFragment
 
+        // If this is user action we test whether it should be prevented before we progress the state.
+        if (!isRepeated && !isInExternalOperationContext && nextSelectedFragment.isPreventNativeSelectionEnabled) {
+            delegate.onNavStateUpdatePrevented(navState, nextSelectedFragment.requireScreenKey)
+            return false
+        }
+
         val stateChanged = updateSelectedFragment(nextSelectedFragment)
 
         val hasTriggeredSpecialEffect =

android/src/main/java/com/swmansion/rnscreens/gamma/tabs/container/TabsContainerDelegate.kt

@@ -32,4 +32,17 @@ internal interface TabsContainerDelegate {
         rejectedNavState: TabsNavState,
         reason: TabsNavStateUpdateRejectionReason,
     )
+
+    /**
+     * Called when a native user action (tap) attempts to select a tab that has
+     * [com.swmansion.rnscreens.gamma.tabs.screen.TabsScreen.preventNativeSelection] enabled.
+     * The navigation state remains unchanged.
+     *
+     * @param currentNavState The currently active navigation state that was kept.
+     * @param preventedScreenKey The screen key of the tab whose selection was prevented.
+     */
+    fun onNavStateUpdatePrevented(
+        currentNavState: TabsNavState,
+        preventedScreenKey: String
+    )
 }

android/src/main/java/com/swmansion/rnscreens/gamma/tabs/host/TabsHost.kt

@@ -182,6 +182,13 @@ class TabsHost(
         )
     }
 
+    override fun onNavStateUpdatePrevented(
+        currentNavState: TabsNavState,
+        preventedScreenKey: String
+    ) {
+        eventEmitter.emitOnTabSelectionPreventedEvent(currentNavState, preventedScreenKey)
+    }
+
     override fun didMountItems(uiManager: UIManager) {
         container.performContainerUpdateIfNeeded()
     }

android/src/main/java/com/swmansion/rnscreens/gamma/tabs/screen/TabsScreenFragment.kt

@@ -11,6 +11,7 @@ class TabsScreenFragment(
     internal val tabsScreen: TabsScreen,
 ) : Fragment() {
     internal val requireScreenKey: String by tabsScreen::requireScreenKey
+    internal val isPreventNativeSelectionEnabled: Boolean by tabsScreen::preventNativeSelection
 
     override fun onCreateView(
         inflater: LayoutInflater,
@@ -44,4 +45,5 @@ class TabsScreenFragment(
         // Handle theme change through RN's Appearance.setColorScheme
         tabsScreen.onFragmentConfigurationChange(this, newConfig)
     }
+
 }