feat(Android, Tabs): Add special effects to bottom tabs on Android

android/src/main/java/com/swmansion/rnscreens/ScreenContainer.kt

@@ -243,6 +243,15 @@ open class ScreenContainer(
         transaction.commitNowAllowingStateLoss()
     }
 
+    fun notifyScreenDetached(screen: Screen) {
+        if (context is ReactContext) {
+            val surfaceId = UIManagerHelper.getSurfaceId(context)
+            UIManagerHelper
+                .getEventDispatcherForReactTag(context as ReactContext, screen.id)
+                ?.dispatchEvent(ScreenDismissedEvent(surfaceId, screen.id))
+        }
+    }
+
     fun notifyTopDetached() {
         val top = topScreen as Screen
         if (context is ReactContext) {

android/src/main/java/com/swmansion/rnscreens/ScreenStack.kt

@@ -109,6 +109,22 @@ class ScreenStack(
         super.removeScreenAt(index)
     }
 
+    // When there is more then one active screen on stack,
+    // pops the screen, so that only one remains
+    // Returns true when any screen was popped
+    // When there was only one screen on stack returns false
+    fun popToRoot(): Boolean {
+        val rootIndex = screenWrappers.indexOfFirst { it.screen.activityState != Screen.ActivityState.INACTIVE }
+        val lastActiveIndex = screenWrappers.indexOfLast { it.screen.activityState != Screen.ActivityState.INACTIVE }
+        if (rootIndex >= 0 && lastActiveIndex > rootIndex) {
+            for (screenIndex in (rootIndex + 1)..lastActiveIndex) {
+                notifyScreenDetached(screenWrappers[screenIndex].screen)
+            }
+            return true
+        }
+        return false
+    }
+
     override fun removeAllScreens() {
         dismissedWrappers.clear()
         super.removeAllScreens()

android/src/main/java/com/swmansion/rnscreens/gamma/helpers/ViewFinder.kt

@@ -0,0 +1,41 @@
+package com.swmansion.rnscreens.gamma.helpers
+
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ScrollView
+import androidx.core.view.isNotEmpty
+import com.swmansion.rnscreens.ScreenStack
+
+object ViewFinder {
+    fun findScrollViewInFirstDescendantChain(view: View): ScrollView? {
+        var currentView: View? = view
+
+        while (currentView != null) {
+            if (currentView is ScrollView) {
+                return currentView
+            } else if (currentView is ViewGroup && currentView.isNotEmpty()) {
+                currentView = currentView.getChildAt(0)
+            } else {
+                break
+            }
+        }
+
+        return null
+    }
+
+    fun findScreenStackInFirstDescendantChain(view: View): ScreenStack? {
+        var currentView: View? = view
+
+        while (currentView != null) {
+            if (currentView is ScreenStack) {
+                return currentView
+            } else if (currentView is ViewGroup && currentView.isNotEmpty()) {
+                currentView = currentView.getChildAt(0)
+            } else {
+                break
+            }
+        }
+
+        return null
+    }
+}

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

@@ -68,6 +68,9 @@ class TabScreen(
         updateMenuItemAttributesIfNeeded(oldValue, newValue)
     }
 
+    var shouldUseRepeatedTabSelectionScrollToTopSpecialEffect: Boolean = true
+    var shouldUseRepeatedTabSelectionPopToRootSpecialEffect: Boolean = true
+
     private fun <T> updateMenuItemAttributesIfNeeded(
         oldValue: T,
         newValue: T,

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

@@ -133,10 +133,28 @@ class TabScreenViewManager :
         value: Boolean,
     ) = Unit
 
+    @ReactProp(name = "specialEffects")
     override fun setSpecialEffects(
         view: TabScreen,
         value: ReadableMap?,
-    ) = Unit
+    ) {
+        var scrollToTop = true
+        var popToRoot = true
+        if (value?.hasKey("repeatedTabSelection") ?: false) {
+            value.getMap("repeatedTabSelection")?.let { repeatedTabSelectionConfig ->
+                if (repeatedTabSelectionConfig.hasKey("scrollToTop")) {
+                    scrollToTop =
+                        repeatedTabSelectionConfig.getBoolean("scrollToTop")
+                }
+                if (repeatedTabSelectionConfig.hasKey("popToRoot")) {
+                    popToRoot =
+                        repeatedTabSelectionConfig.getBoolean("popToRoot")
+                }
+            }
+        }
+        view.shouldUseRepeatedTabSelectionPopToRootSpecialEffect = popToRoot
+        view.shouldUseRepeatedTabSelectionScrollToTopSpecialEffect = scrollToTop
+    }
 
     override fun setOverrideScrollViewContentInsetAdjustmentBehavior(
         view: TabScreen,

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

@@ -16,6 +16,7 @@ import com.facebook.react.uimanager.ThemedReactContext
 import com.google.android.material.bottomnavigation.BottomNavigationView
 import com.swmansion.rnscreens.BuildConfig
 import com.swmansion.rnscreens.gamma.helpers.FragmentManagerHelper
+import com.swmansion.rnscreens.gamma.helpers.ViewFinder
 import com.swmansion.rnscreens.gamma.helpers.ViewIdGenerator
 import com.swmansion.rnscreens.safearea.EdgeInsets
 import com.swmansion.rnscreens.safearea.SafeAreaProvider
@@ -92,7 +93,29 @@ class TabsHost(
         }
     }
 
+    private inner class SpecialEffectsHandler {
+        fun handleRepeatedTabSelection(): Boolean {
+            val contentView = [email protected]
+            val selectedTabFragment = [email protected]
+            if (selectedTabFragment.tabScreen.shouldUseRepeatedTabSelectionPopToRootSpecialEffect) {
+                val screenStack = ViewFinder.findScreenStackInFirstDescendantChain(contentView)
+                if (screenStack != null && screenStack.popToRoot()) {
+                    return true
+                }
+            }
+            if (selectedTabFragment.tabScreen.shouldUseRepeatedTabSelectionScrollToTopSpecialEffect) {
+                val scrollView = ViewFinder.findScrollViewInFirstDescendantChain(contentView)
+                if (scrollView != null && scrollView.scrollY > 0) {
+                    scrollView.smoothScrollTo(scrollView.scrollX, 0)
+                    return true
+                }
+            }
+            return false
+        }
+    }
+
     private val containerUpdateCoordinator = ContainerUpdateCoordinator()
+    private val specialEffectsHandler = SpecialEffectsHandler()
 
     private val wrappedContext =
         ContextThemeWrapper(
@@ -128,6 +151,9 @@ class TabsHost(
 
     private val tabScreenFragments: MutableList<TabScreenFragment> = arrayListOf()
 
+    private val currentFocusedTab: TabScreenFragment
+        get() = checkNotNull(tabScreenFragments.find { it.tabScreen.isFocusedTab }) { "[RNScreens] No focused tab present" }
+
     private var lastAppliedUiMode: Int? = null
 
     private var isLayoutEnqueued: Boolean = false
@@ -226,8 +252,10 @@ class TabsHost(
         bottomNavigationView.setOnItemSelectedListener { item ->
             RNSLog.d(TAG, "Item selected $item")
             val fragment = getFragmentForMenuItemId(item.itemId)
-            val tabKey = fragment?.tabScreen?.tabKey ?: "undefined"
-            eventEmitter.emitOnNativeFocusChange(tabKey)
+            if (fragment != currentFocusedTab || !specialEffectsHandler.handleRepeatedTabSelection()) {
+                val tabKey = fragment?.tabScreen?.tabKey ?: "undefined"
+                eventEmitter.emitOnNativeFocusChange(tabKey)
+            }
             true
         }
     }
@@ -334,8 +362,7 @@ class TabsHost(
     }
 
     private fun updateSelectedTab() {
-        val newFocusedTab =
-            checkNotNull(tabScreenFragments.find { it.tabScreen.isFocusedTab }) { "[RNScreens] No focused tab present" }
+        val newFocusedTab = currentFocusedTab
 
         check(requireFragmentManager.fragments.size <= 1) { "[RNScreens] There can be only a single focused tab" }
         val oldFocusedTab = requireFragmentManager.fragments.firstOrNull()

apps/src/tests/TestBottomTabs/index.tsx

@@ -38,11 +38,11 @@ const TAB_CONFIGS: TabConfiguration[] = [
         ios: {
           type: 'sfSymbol',
           name: 'house.fill',
-        }, 
+        },
         android: {
           type: 'imageSource',
           imageSource: require('../../../assets/variableIcons/icon_fill.png'),
-        }
+        },
       },
       selectedIcon: {
         type: 'sfSymbol',
@@ -105,11 +105,11 @@ const TAB_CONFIGS: TabConfiguration[] = [
         ios: {
           type: 'templateSource',
           templateSource: require('../../../assets/variableIcons/icon.png'),
-        }, 
+        },
         android: {
           type: 'drawableResource',
           name: 'sym_call_missed',
-        }
+        },
       },
       selectedIcon: {
         type: 'templateSource',
@@ -148,7 +148,7 @@ const TAB_CONFIGS: TabConfiguration[] = [
         shared: {
           type: 'imageSource',
           imageSource: require('../../../assets/variableIcons/icon.png'),
-        }
+        },
       },
       selectedIcon: {
         type: 'imageSource',
@@ -171,8 +171,8 @@ const TAB_CONFIGS: TabConfiguration[] = [
         },
         android: {
           type: 'drawableResource',
-          name: 'custom_home_icon'
-        }
+          name: 'custom_home_icon',
+        },
       },
       selectedIcon: {
         type: 'sfSymbol',
@@ -181,6 +181,11 @@ const TAB_CONFIGS: TabConfiguration[] = [
       title: 'Tab4',
       systemItem: 'search', // iOS specific
       badgeValue: '123',
+      specialEffects: {
+        repeatedTabSelection: {
+          popToRoot: false,
+        },
+      },
     },
     component: Tab4,
   },

apps/src/tests/TestBottomTabs/tabs/Tab4.tsx

@@ -64,7 +64,7 @@ export function Tab4() {
         <Stack.Screen
           name="Screen1"
           component={Screen1}
-          options={{ headerTransparent: true }}
+          options={{ headerTransparent: false }}
         />
         <Stack.Screen
           name="Screen2"

src/components/bottom-tabs/BottomTabsScreen.types.ts

@@ -467,12 +467,16 @@ export interface BottomTabsScreenProps {
    * `popToRoot` has priority over `scrollToTop`.
    *
    * @default All special effects are enabled by default.
-   *
-   * @platform ios
    */
   specialEffects?: {
     repeatedTabSelection?: {
+      /**
+       * @default true
+       */
       popToRoot?: boolean;
+      /**
+       * @default true
+       */
       scrollToTop?: boolean;
     };
   };