refact(Android): allow for different fragment types inside ScreenCont…

…ainer (software-mansion#1887)

## Description

This PR is laying out ground work under not-so-distant Android modal &
bottom sheet implementation.

Currently `ScreenContainer<T: ScreenFragment>: ViewGroup` (and thus
`ScreenStack: ScreenContainer<ScreenStackFragment>`) operates on
`ScreenFragment: Fragment` objects, making it impossible to use any
other `Fragment` subclass with the stack (only single inheritance is
possible on JVM).

This PR changes the situation by introducing `ScreenFragmentWrapper`
interface which both:

1. holds the reference to underlaying `Fragment`
2. provides additional API previously directly attached to the
`ScreenFragment`

Also introduced `ScreenStackFragmentWrapper` extends
`ScreenFragmentWrapper` with API previously attached to
`ScreenStackFragment`.

Thereafter by implementing such interface by the fragment subclass
itself we can have both of worlds:

1. Customized fragment behaviour
2. Implementation of all methods required for fragment<->container
communication.

Disclaimer: *I have decided to split "Android modals PR" into few
smaller ones to reduce its size and complexity. I won't use "stack PR"
technique to spare myself whole bunch of rebasing & conflict resolving.*

## Changes

1. `ScreenContainer` is no longer parameterized with `T:
ScreenFragment`. It uses `ScreenFragmentWrapper` as screen-primitve base
type now.
2. Our fragment types `ScreenFragment` & `ScreenStackFragment` now
implement `ScreenFragmentWrapper` & `ScreenStackFragmentWrapper`
interfaces respectively.
3. `ScreenContainer` has access to the fragments it operates on
(fragment API) via `ScreenFragmentWrapper.fragment` property.
4. Our custom methods previously implemented directly on `Fragment`
subclass are exposed via the new interfaces so `ScreenContainer` still
has access to them.

## Test code and steps to reproduce

See that test examples build & CI passes.

I did some manual testing in our example apps & didn't notice any
regression.

## Checklist

- [x] Ensured that CI passes

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

@@ -0,0 +1,7 @@
+package com.swmansion.rnscreens
+
+import androidx.fragment.app.Fragment
+
+interface FragmentHolder {
+    val fragment: Fragment
+}

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

@@ -9,15 +9,18 @@ import android.view.ViewGroup
 import android.view.WindowManager
 import android.webkit.WebView
 import androidx.core.view.children
+import androidx.fragment.app.Fragment
 import com.facebook.react.bridge.GuardedRunnable
 import com.facebook.react.bridge.ReactContext
 import com.facebook.react.uimanager.UIManagerModule
 
 @SuppressLint("ViewConstructor")
 class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(context) {
+    val fragment: Fragment?
+        get() = fragmentWrapper?.fragment
 
-    var fragment: ScreenFragment? = null
-    var container: ScreenContainer<*>? = null
+    var fragmentWrapper: ScreenFragmentWrapper? = null
+    var container: ScreenContainer? = null
     var activityState: ActivityState? = null
         private set
     private var mTransitioning = false
@@ -150,7 +153,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
             else -> ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED
         }
 
-        fragment?.let { ScreenWindowTraits.setOrientation(this, it.tryGetActivity()) }
+        fragmentWrapper?.let { ScreenWindowTraits.setOrientation(this, it.tryGetActivity()) }
     }
 
     // Accepts one of 4 accessibility flags
@@ -167,7 +170,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetStatusBarAppearance()
             }
             mStatusBarStyle = statusBarStyle
-            fragment?.let { ScreenWindowTraits.setStyle(this, it.tryGetActivity(), it.tryGetContext()) }
+            fragmentWrapper?.let { ScreenWindowTraits.setStyle(this, it.tryGetActivity(), it.tryGetContext()) }
         }
 
     var isStatusBarHidden: Boolean?
@@ -177,7 +180,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetStatusBarAppearance()
             }
             mStatusBarHidden = statusBarHidden
-            fragment?.let { ScreenWindowTraits.setHidden(this, it.tryGetActivity()) }
+            fragmentWrapper?.let { ScreenWindowTraits.setHidden(this, it.tryGetActivity()) }
         }
 
     var isStatusBarTranslucent: Boolean?
@@ -187,7 +190,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetStatusBarAppearance()
             }
             mStatusBarTranslucent = statusBarTranslucent
-            fragment?.let {
+            fragmentWrapper?.let {
                 ScreenWindowTraits.setTranslucent(
                     this,
                     it.tryGetActivity(),
@@ -203,7 +206,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetStatusBarAppearance()
             }
             mStatusBarColor = statusBarColor
-            fragment?.let { ScreenWindowTraits.setColor(this, it.tryGetActivity(), it.tryGetContext()) }
+            fragmentWrapper?.let { ScreenWindowTraits.setColor(this, it.tryGetActivity(), it.tryGetContext()) }
         }
 
     var navigationBarColor: Int?
@@ -213,7 +216,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetNavigationBarAppearance()
             }
             mNavigationBarColor = navigationBarColor
-            fragment?.let { ScreenWindowTraits.setNavigationBarColor(this, it.tryGetActivity()) }
+            fragmentWrapper?.let { ScreenWindowTraits.setNavigationBarColor(this, it.tryGetActivity()) }
         }
 
     var isNavigationBarHidden: Boolean?
@@ -223,7 +226,7 @@ class Screen constructor(context: ReactContext?) : FabricEnabledViewGroup(contex
                 ScreenWindowTraits.applyDidSetNavigationBarAppearance()
             }
             mNavigationBarHidden = navigationBarHidden
-            fragment?.let {
+            fragmentWrapper?.let {
                 ScreenWindowTraits.setNavigationBarHidden(
                     this,
                     it.tryGetActivity(),

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

@@ -16,9 +16,9 @@ import com.facebook.react.modules.core.ChoreographerCompat
 import com.facebook.react.modules.core.ReactChoreographer
 import com.swmansion.rnscreens.Screen.ActivityState
 
-open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(context) {
+open class ScreenContainer(context: Context?) : ViewGroup(context) {
     @JvmField
-    protected val mScreenFragments = ArrayList<T>()
+    protected val mScreenFragments = ArrayList<ScreenFragmentWrapper>()
     @JvmField
     protected var mFragmentManager: FragmentManager? = null
     private var mIsAttached = false
@@ -34,7 +34,7 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
             layout(left, top, right, bottom)
         }
     }
-    private var mParentScreenFragment: ScreenFragment? = null
+    private var mParentScreenFragment: ScreenFragmentWrapper? = null
 
     override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
         var i = 0
@@ -87,14 +87,11 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
         performUpdatesNow()
     }
 
-    protected open fun adapt(screen: Screen): T {
-        @Suppress("UNCHECKED_CAST")
-        return ScreenFragment(screen) as T
-    }
+    protected open fun adapt(screen: Screen): ScreenFragmentWrapper = ScreenFragment(screen)
 
     fun addScreen(screen: Screen, index: Int) {
         val fragment = adapt(screen)
-        screen.fragment = fragment
+        screen.fragmentWrapper = fragment
         mScreenFragments.add(index, fragment)
         screen.container = this
         onScreenChanged()
@@ -119,6 +116,8 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
 
     fun getScreenAt(index: Int): Screen = mScreenFragments[index].screen
 
+    fun getScreenFragmentWrapperAt(index: Int): ScreenFragmentWrapper = mScreenFragments[index]
+
     open val topScreen: Screen?
         get() = mScreenFragments.firstOrNull { getActivityState(it) === ActivityState.ON_TOP }?.screen
 
@@ -174,10 +173,10 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
         // Otherwise we expect to connect directly with root view and get root fragment manager
         if (parent is Screen) {
             checkNotNull(
-                parent.fragment?.let { screenFragment ->
-                    mParentScreenFragment = screenFragment
-                    screenFragment.registerChildScreenContainer(this)
-                    setFragmentManager(screenFragment.childFragmentManager)
+                parent.fragmentWrapper?.let { fragmentWrapper ->
+                    mParentScreenFragment = fragmentWrapper
+                    fragmentWrapper.addChildScreenContainer(this)
+                    setFragmentManager(fragmentWrapper.fragment.childFragmentManager)
                 }
             ) { "Parent Screen does not have its Fragment attached" }
         } else {
@@ -197,19 +196,19 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
             .setReorderingAllowed(true)
     }
 
-    private fun attachScreen(transaction: FragmentTransaction, screenFragment: ScreenFragment) {
-        transaction.add(id, screenFragment)
+    private fun attachScreen(transaction: FragmentTransaction, fragment: Fragment) {
+        transaction.add(id, fragment)
     }
 
-    private fun detachScreen(transaction: FragmentTransaction, screenFragment: ScreenFragment) {
-        transaction.remove(screenFragment)
+    private fun detachScreen(transaction: FragmentTransaction, fragment: Fragment) {
+        transaction.remove(fragment)
     }
 
-    private fun getActivityState(screenFragment: ScreenFragment): ActivityState? =
-        screenFragment.screen.activityState
+    private fun getActivityState(screenFragmentWrapper: ScreenFragmentWrapper): ActivityState? =
+        screenFragmentWrapper.screen.activityState
 
-    open fun hasScreen(screenFragment: ScreenFragment?): Boolean =
-        mScreenFragments.contains(screenFragment)
+    open fun hasScreen(screenFragmentWrapper: ScreenFragmentWrapper?): Boolean =
+        mScreenFragments.contains(screenFragmentWrapper)
 
     override fun onAttachedToWindow() {
         super.onAttachedToWindow()
@@ -246,7 +245,7 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
             }
         }
 
-        mParentScreenFragment?.unregisterChildScreenContainer(this)
+        mParentScreenFragment?.removeChildScreenContainer(this)
         mParentScreenFragment = null
 
         super.onDetachedFromWindow()
@@ -320,13 +319,13 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
                     "mFragmentManager is null when performing update in ScreenContainer"
                 }.fragments
             )
-            for (screenFragment in mScreenFragments) {
-                if (getActivityState(screenFragment) === ActivityState.INACTIVE &&
-                    screenFragment.isAdded
+            for (fragmentWrapper in mScreenFragments) {
+                if (getActivityState(fragmentWrapper) === ActivityState.INACTIVE &&
+                    fragmentWrapper.fragment.isAdded
                 ) {
-                    detachScreen(it, screenFragment)
+                    detachScreen(it, fragmentWrapper.fragment)
                 }
-                orphaned.remove(screenFragment)
+                orphaned.remove(fragmentWrapper.fragment)
             }
             if (orphaned.isNotEmpty()) {
                 val orphanedAry = orphaned.toTypedArray()
@@ -344,30 +343,30 @@ open class ScreenContainer<T : ScreenFragment>(context: Context?) : ViewGroup(co
 
             // attach newly activated screens
             var addedBefore = false
-            val pendingFront: ArrayList<T> = ArrayList()
+            val pendingFront: ArrayList<ScreenFragmentWrapper> = ArrayList()
 
-            for (screenFragment in mScreenFragments) {
-                val activityState = getActivityState(screenFragment)
-                if (activityState !== ActivityState.INACTIVE && !screenFragment.isAdded) {
+            for (fragmentWrapper in mScreenFragments) {
+                val activityState = getActivityState(fragmentWrapper)
+                if (activityState !== ActivityState.INACTIVE && !fragmentWrapper.fragment.isAdded) {
                     addedBefore = true
-                    attachScreen(it, screenFragment)
+                    attachScreen(it, fragmentWrapper.fragment)
                 } else if (activityState !== ActivityState.INACTIVE && addedBefore) {
                     // we detach the screen and then reattach it later to make it appear on front
-                    detachScreen(it, screenFragment)
-                    pendingFront.add(screenFragment)
+                    detachScreen(it, fragmentWrapper.fragment)
+                    pendingFront.add(fragmentWrapper)
                 }
-                screenFragment.screen.setTransitioning(transitioning)
+                fragmentWrapper.screen.setTransitioning(transitioning)
             }
 
             for (screenFragment in pendingFront) {
-                attachScreen(it, screenFragment)
+                attachScreen(it, screenFragment.fragment)
             }
 
             it.commitNowAllowingStateLoss()
         }
     }
 
     protected open fun notifyContainerUpdate() {
-        topScreen?.fragment?.onContainerUpdate()
+        topScreen?.fragmentWrapper?.onContainerUpdate()
     }
 }

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

@@ -8,27 +8,27 @@ import com.facebook.react.uimanager.ThemedReactContext
 import com.facebook.react.uimanager.ViewGroupManager
 
 @ReactModule(name = ScreenContainerViewManager.REACT_CLASS)
-class ScreenContainerViewManager : ViewGroupManager<ScreenContainer<*>>() {
+class ScreenContainerViewManager : ViewGroupManager<ScreenContainer>() {
     override fun getName(): String = REACT_CLASS
 
-    override fun createViewInstance(reactContext: ThemedReactContext): ScreenContainer<ScreenFragment> = ScreenContainer(reactContext)
+    override fun createViewInstance(reactContext: ThemedReactContext): ScreenContainer = ScreenContainer(reactContext)
 
-    override fun addView(parent: ScreenContainer<*>, child: View, index: Int) {
+    override fun addView(parent: ScreenContainer, child: View, index: Int) {
         require(child is Screen) { "Attempt attach child that is not of type RNScreens" }
         parent.addScreen(child, index)
     }
 
-    override fun removeViewAt(parent: ScreenContainer<*>, index: Int) {
+    override fun removeViewAt(parent: ScreenContainer, index: Int) {
         parent.removeScreenAt(index)
     }
 
-    override fun removeAllViews(parent: ScreenContainer<*>) {
+    override fun removeAllViews(parent: ScreenContainer) {
         parent.removeAllScreens()
     }
 
-    override fun getChildCount(parent: ScreenContainer<*>): Int = parent.screenCount
+    override fun getChildCount(parent: ScreenContainer): Int = parent.screenCount
 
-    override fun getChildAt(parent: ScreenContainer<*>, index: Int): View = parent.getScreenAt(index)
+    override fun getChildAt(parent: ScreenContainer, index: Int): View = parent.getScreenAt(index)
 
     override fun createShadowNodeInstance(context: ReactApplicationContext): LayoutShadowNode = ScreensShadowNode(context)
 

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

@@ -0,0 +1,21 @@
+package com.swmansion.rnscreens
+
+interface ScreenEventDispatcher {
+    fun canDispatchLifecycleEvent(event: ScreenFragment.ScreenLifecycleEvent): Boolean
+    fun updateLastEventDispatched(event: ScreenFragment.ScreenLifecycleEvent)
+
+    /**
+     * Dispatches given screen lifecycle event to JS using screen from given fragment `fragmentWrapper`
+     */
+    fun dispatchLifecycleEvent(event: ScreenFragment.ScreenLifecycleEvent, fragmentWrapper: ScreenFragmentWrapper)
+
+    /**
+     * Dispatches given screen lifecycle event from all non-empty child containers to JS
+     */
+    fun dispatchLifecycleEventInChildContainers(event: ScreenFragment.ScreenLifecycleEvent)
+
+    fun dispatchHeaderBackButtonClickedEvent()
+    fun dispatchTransitionProgressEvent(alpha: Float, closing: Boolean)
+
+    // Concrete dispatchers
+}