Addresses fragments tracking and different bugs/warnings

Summary:
^

After this change lands, it is safe to remove most of the Stetho fragment support types.

Reviewed By: LukeDefeo

Differential Revision: D39460121

fbshipit-source-id: 0e7d4ce71e828ee7bc9c6e945b8fe27dbd6f08f8

android/plugins/litho/src/main/java/com/facebook/flipper/plugins/uidebugger/litho/LithoObserver.kt

@@ -9,8 +9,8 @@ package com.facebook.flipper.plugins.uidebugger.litho
 
 import android.util.Log
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.TreeObserver
 import com.facebook.flipper.plugins.uidebugger.core.Context
+import com.facebook.flipper.plugins.uidebugger.observers.TreeObserver
 import com.facebook.flipper.plugins.uidebugger.observers.TreeObserverBuilder
 import com.facebook.litho.LithoView
 

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/ActivityTracker.kt

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.core
+
+import android.annotation.SuppressLint
+import android.app.Activity
+import android.app.Application
+import android.os.Build
+import android.os.Bundle
+import java.lang.ref.WeakReference
+import java.lang.reflect.Field
+import java.lang.reflect.Method
+
+object ActivityTracker : Application.ActivityLifecycleCallbacks {
+  interface ActivityStackChangedListener {
+    fun onActivityAdded(activity: Activity, stack: List<Activity>)
+    fun onActivityStackChanged(stack: List<Activity>)
+    fun onActivityDestroyed(activity: Activity, stack: List<Activity>)
+  }
+
+  private val activities: MutableList<WeakReference<Activity>> = mutableListOf()
+  private val trackedActivities: MutableSet<Int> = mutableSetOf()
+  private var activityStackChangedListener: ActivityStackChangedListener? = null
+
+  fun setActivityStackChangedListener(listener: ActivityStackChangedListener?) {
+    activityStackChangedListener = listener
+  }
+
+  fun start(application: Application) {
+    initialiseActivities()
+    application.registerActivityLifecycleCallbacks(this)
+  }
+
+  private fun trackActivity(activity: Activity) {
+    if (trackedActivities.contains(System.identityHashCode(activity))) {
+      return
+    }
+
+    trackedActivities.add(System.identityHashCode(activity))
+    activities.add(WeakReference<Activity>(activity))
+
+    FragmentTracker.trackFragmentsOfActivity(activity)
+
+    activityStackChangedListener?.onActivityAdded(activity, this.activitiesStack)
+    activityStackChangedListener?.onActivityStackChanged(this.activitiesStack)
+  }
+
+  private fun untrackActivity(activity: Activity) {
+    trackedActivities.remove(System.identityHashCode(activity))
+    val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
+
+    while (activityIterator.hasNext()) {
+      if (activityIterator.next().get() === activity) {
+        activityIterator.remove()
+      }
+    }
+
+    FragmentTracker.untrackFragmentsOfActivity(activity)
+
+    activityStackChangedListener?.onActivityDestroyed(activity, this.activitiesStack)
+    activityStackChangedListener?.onActivityStackChanged(this.activitiesStack)
+  }
+
+  override fun onActivityCreated(activity: Activity, bundle: Bundle?) {
+    trackActivity(activity)
+  }
+
+  override fun onActivityStarted(activity: Activity) {
+    trackActivity(activity)
+  }
+
+  override fun onActivityResumed(activity: Activity) {}
+
+  override fun onActivityPaused(activity: Activity) {}
+
+  override fun onActivityStopped(activity: Activity) {}
+
+  override fun onActivitySaveInstanceState(activity: Activity, bundle: Bundle) {}
+
+  override fun onActivityDestroyed(activity: Activity) {
+    untrackActivity(activity)
+  }
+
+  val activitiesStack: List<Activity>
+    get() {
+      val stack: MutableList<Activity> = ArrayList(activities.size)
+      val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
+      while (activityIterator.hasNext()) {
+        val activity: Activity? = activityIterator.next().get()
+        if (activity == null) {
+          activityIterator.remove()
+        } else {
+          stack.add(activity)
+        }
+      }
+      return stack
+    }
+
+  @SuppressLint("PrivateApi", "DiscouragedPrivateApi")
+  fun initialiseActivities() {
+    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
+      return
+    }
+
+    try {
+      val activityThreadClass: Class<*> = Class.forName("android.app.ActivityThread")
+      val currentActivityThreadMethod: Method =
+          activityThreadClass.getMethod("currentActivityThread")
+      val currentActivityThread: Any? = currentActivityThreadMethod.invoke(null)
+
+      currentActivityThread?.let { activityThread ->
+        val mActivitiesField: Field = activityThreadClass.getDeclaredField("mActivities")
+        mActivitiesField.isAccessible = true
+        val mActivities = mActivitiesField.get(activityThread) as android.util.ArrayMap<*, *>
+        for (record in mActivities.values) {
+          val recordClass: Class<*> = record.javaClass
+          val activityField: Field = recordClass.getDeclaredField("activity")
+          activityField.isAccessible = true
+
+          val activity = activityField.get(record)
+          if (activity != null && activity is Activity) {
+            trackActivity(activity)
+          }
+        }
+      }
+    } catch (e: Exception) {}
+  }
+}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/ApplicationRef.kt

@@ -9,68 +9,25 @@ package com.facebook.flipper.plugins.uidebugger.core
 
 import android.app.Activity
 import android.app.Application
-import android.os.Bundle
 import android.view.View
-import java.lang.ref.WeakReference
 
-class ApplicationRef(val application: Application) : Application.ActivityLifecycleCallbacks {
+class ApplicationRef(val application: Application) {
-  interface ActivityStackChangedListener {
+  init {
-    fun onActivityAdded(activity: Activity, stack: List<Activity>)
+    ActivityTracker.start(application)
-    fun onActivityStackChanged(stack: List<Activity>)
-    fun onActivityDestroyed(activity: Activity, stack: List<Activity>)
   }
 
-  val rootsResolver: RootViewResolver
+  val rootsResolver: RootViewResolver = RootViewResolver()
-  private val activities: MutableList<WeakReference<Activity>>
-  private var activityStackChangedlistener: ActivityStackChangedListener? = null
-
-  override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
-    activities.add(WeakReference<Activity>(activity))
-    activityStackChangedlistener?.onActivityAdded(activity, this.activitiesStack)
-    activityStackChangedlistener?.onActivityStackChanged(this.activitiesStack)
-  }
-  override fun onActivityStarted(activity: Activity) {}
-  override fun onActivityResumed(activity: Activity) {}
-  override fun onActivityPaused(activity: Activity) {}
-  override fun onActivityStopped(activity: Activity) {}
-  override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}
-  override fun onActivityDestroyed(activity: Activity) {
-    val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
-
-    while (activityIterator.hasNext()) {
-      if (activityIterator.next().get() === activity) {
-        activityIterator.remove()
-      }
-    }
-
-    activityStackChangedlistener?.onActivityDestroyed(activity, this.activitiesStack)
-    activityStackChangedlistener?.onActivityStackChanged(this.activitiesStack)
-  }
-
-  fun setActivityStackChangedListener(listener: ActivityStackChangedListener?) {
-    activityStackChangedlistener = listener
-  }
 
   val activitiesStack: List<Activity>
     get() {
-      val stack: MutableList<Activity> = ArrayList<Activity>(activities.size)
+      return ActivityTracker.activitiesStack
-      val activityIterator: MutableIterator<WeakReference<Activity>> = activities.iterator()
-      while (activityIterator.hasNext()) {
-        val activity: Activity? = activityIterator.next().get()
-        if (activity == null) {
-          activityIterator.remove()
-        } else {
-          stack.add(activity)
-        }
-      }
-      return stack
     }
 
   val rootViews: List<View>
     get() {
-      val roots = rootsResolver.listActiveRootViews()
+      val activeRootViews = rootsResolver.listActiveRootViews()
-      roots?.let { roots ->
+      activeRootViews?.let { roots ->
-        val viewRoots: MutableList<View> = ArrayList<View>(roots.size)
+        val viewRoots: MutableList<View> = ArrayList(roots.size)
         for (root in roots) {
           viewRoots.add(root.view)
         }
@@ -79,10 +36,4 @@ class ApplicationRef(val application: Application) : Application.ActivityLifecyc
 
       return emptyList()
     }
-
-  init {
-    rootsResolver = RootViewResolver()
-    application.registerActivityLifecycleCallbacks(this)
-    activities = ArrayList<WeakReference<Activity>>()
-  }
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/FragmentTracker.kt

@@ -0,0 +1,271 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.core
+
+import android.app.Activity
+import android.os.Build
+import android.os.Bundle
+import android.view.View
+import java.lang.ref.WeakReference
+
+object FragmentTracker {
+
+  class FragmentRef {
+    val supportFragment: WeakReference<androidx.fragment.app.Fragment>?
+    val frameworkFragment: WeakReference<android.app.Fragment>?
+    val isSupportFragment: Boolean
+
+    constructor(supportFragment: androidx.fragment.app.Fragment) {
+      this.supportFragment = WeakReference(supportFragment)
+      this.frameworkFragment = null
+      this.isSupportFragment = true
+    }
+
+    constructor(frameworkFragment: android.app.Fragment) {
+      this.supportFragment = null
+      this.frameworkFragment = WeakReference(frameworkFragment)
+      this.isSupportFragment = false
+    }
+
+    override fun hashCode(): Int {
+      if (isSupportFragment) {
+        val fragment = supportFragment?.get()
+        fragment?.let { f ->
+          return System.identityHashCode(f)
+        }
+      } else {
+        val fragment = frameworkFragment?.get()
+        fragment?.let { f ->
+          return System.identityHashCode(f)
+        }
+      }
+      return -1
+    }
+
+    override fun equals(other: Any?): Boolean {
+      if (this === other) return true
+      if (javaClass != other?.javaClass) return false
+
+      other as FragmentRef
+
+      if (isSupportFragment != other.isSupportFragment) return false
+      if (isSupportFragment && (supportFragment != other.supportFragment)) return false
+      else if (frameworkFragment != other.frameworkFragment) return false
+
+      return true
+    }
+
+    val view: View?
+      get() {
+        if (isSupportFragment) {
+          val fragment = supportFragment?.get()
+          fragment?.let { f ->
+            return f.view
+          }
+        } else {
+          val fragment = frameworkFragment?.get()
+          fragment?.let { f ->
+            return f.view
+          }
+        }
+
+        return null
+      }
+
+    override fun toString(): String {
+      if (isSupportFragment) {
+        val fragment = supportFragment?.get()
+        fragment?.let { f ->
+          return "$f"
+        }
+      } else {
+        val fragment = frameworkFragment?.get()
+        fragment?.let { f ->
+          return "$f"
+        }
+      }
+      return "unknown"
+    }
+  }
+
+  private val activityFragments: MutableMap<Int, MutableSet<FragmentRef>> = mutableMapOf()
+  private val viewFragment: MutableMap<Int, FragmentRef> = mutableMapOf()
+
+  private val supportLibraryLifecycleTracker =
+      object : androidx.fragment.app.FragmentManager.FragmentLifecycleCallbacks() {
+        override fun onFragmentAttached(
+            fm: androidx.fragment.app.FragmentManager,
+            f: androidx.fragment.app.Fragment,
+            context: android.content.Context
+        ) {
+          super.onFragmentAttached(fm, f, context)
+
+          f.activity?.let { activity ->
+            val fragmentRef = FragmentRef(f)
+            activityFragments[System.identityHashCode(activity)]?.add(fragmentRef)
+          }
+        }
+
+        override fun onFragmentViewCreated(
+            fm: androidx.fragment.app.FragmentManager,
+            f: androidx.fragment.app.Fragment,
+            v: View,
+            savedInstanceState: Bundle?
+        ) {
+          super.onFragmentViewCreated(fm, f, v, savedInstanceState)
+
+          val fragmentRef = FragmentRef(f)
+          viewFragment[System.identityHashCode(v)] = fragmentRef
+        }
+
+        override fun onFragmentViewDestroyed(
+            fm: androidx.fragment.app.FragmentManager,
+            f: androidx.fragment.app.Fragment
+        ) {
+          super.onFragmentViewDestroyed(fm, f)
+          for (entry in viewFragment) {
+            if (entry.value.supportFragment == f) {
+              viewFragment.remove(entry.key)
+              break
+            }
+          }
+        }
+
+        override fun onFragmentDetached(
+            fm: androidx.fragment.app.FragmentManager,
+            f: androidx.fragment.app.Fragment
+        ) {
+          super.onFragmentDetached(fm, f)
+
+          f.activity?.let { activity ->
+            val fragmentRef = FragmentRef(f)
+            activityFragments[System.identityHashCode(activity)]?.remove(fragmentRef)
+          }
+
+          f.view?.let { view -> viewFragment.remove(System.identityHashCode(view)) }
+        }
+      }
+
+  private var frameworkLifecycleTracker: Any? = null
+
+  fun trackFragmentsOfActivity(activity: Activity) {
+    activityFragments[System.identityHashCode(activity)] = mutableSetOf()
+    if (activity is androidx.fragment.app.FragmentActivity) {
+      activity.supportFragmentManager.registerFragmentLifecycleCallbacks(
+          supportLibraryLifecycleTracker, true)
+    } else {
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && frameworkLifecycleTracker != null) {
+        activity.fragmentManager.registerFragmentLifecycleCallbacks(
+            frameworkLifecycleTracker as android.app.FragmentManager.FragmentLifecycleCallbacks,
+            true)
+      }
+    }
+  }
+
+  fun untrackFragmentsOfActivity(activity: Activity) {
+    activityFragments[System.identityHashCode(activity)]?.let { fragments ->
+      fragments.forEach { f ->
+        f.view?.let { view -> viewFragment.remove(System.identityHashCode(view)) }
+      }
+    }
+    activityFragments.remove(System.identityHashCode(activity))
+
+    if (activity is androidx.fragment.app.FragmentActivity) {
+      activity.supportFragmentManager.unregisterFragmentLifecycleCallbacks(
+          supportLibraryLifecycleTracker)
+    } else {
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && frameworkLifecycleTracker != null) {
+        activity.fragmentManager.unregisterFragmentLifecycleCallbacks(
+            frameworkLifecycleTracker as android.app.FragmentManager.FragmentLifecycleCallbacks)
+      }
+    }
+  }
+
+  fun getFragment(view: View): Any? {
+    val key = System.identityHashCode(view)
+    val fragmentRef = viewFragment[key]
+
+    fragmentRef?.let { fragment ->
+      fragment.supportFragment?.get()?.let { f ->
+        return f
+      }
+
+      fragment.frameworkFragment?.get()?.let { f ->
+        return f
+      }
+    }
+
+    return null
+  }
+
+  fun getDialogFragments(activity: Activity): List<Any> {
+    val key = System.identityHashCode(activity)
+    val fragments = mutableListOf<Any>()
+
+    activityFragments[key]?.forEach { fragmentRef ->
+      fragmentRef.supportFragment?.get()?.let { fragment ->
+        if (androidx.fragment.app.DialogFragment::class.java.isInstance(fragment)) {
+          fragments.add(fragmentRef)
+        }
+      }
+      fragmentRef.frameworkFragment?.get()?.let { fragment ->
+        if (android.app.DialogFragment::class.java.isInstance(fragment)) {
+          fragments.add(fragmentRef)
+        }
+      }
+    }
+
+    return fragments
+  }
+
+  init {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O &&
+        Class.forName("android.app.FragmentManager\$FragmentLifecycleCallbacks") != null) {
+      frameworkLifecycleTracker =
+          object : android.app.FragmentManager.FragmentLifecycleCallbacks() {
+            override fun onFragmentAttached(
+                fm: android.app.FragmentManager?,
+                f: android.app.Fragment?,
+                context: android.content.Context?
+            ) {
+              super.onFragmentAttached(fm, f, context)
+              f?.let { fragment ->
+                val fragmentRef = FragmentRef(fragment)
+                activityFragments[System.identityHashCode(fragment.activity)]?.add(fragmentRef)
+              }
+            }
+
+            override fun onFragmentViewCreated(
+                fm: android.app.FragmentManager?,
+                f: android.app.Fragment?,
+                v: View?,
+                savedInstanceState: Bundle?
+            ) {
+              super.onFragmentViewCreated(fm, f, v, savedInstanceState)
+              if (f != null && v != null) {
+                val fragmentRef = FragmentRef(f)
+                viewFragment[System.identityHashCode(v)] = fragmentRef
+              }
+            }
+
+            override fun onFragmentDetached(
+                fm: android.app.FragmentManager?,
+                f: android.app.Fragment?
+            ) {
+              super.onFragmentDetached(fm, f)
+              f?.let { fragment ->
+                val fragmentRef = FragmentRef(fragment)
+                activityFragments[System.identityHashCode(fragment.activity)]?.remove(fragmentRef)
+
+                fragment.view?.let { view -> viewFragment.remove(System.identityHashCode(view)) }
+              }
+            }
+          }
+    }
+  }
+}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/LayoutTraversal.kt

@@ -46,7 +46,7 @@ class LayoutTraversal(
           val childDescriptor =
               descriptorRegister.descriptorForClassUnsafe(child::class.java).asAny()
           childrenIds.add(childDescriptor.getId(child))
-          // if there is an active child then dont traverse it
+          // if there is an active child then don't traverse it
           if (activeChild == null) {
             stack.add(child)
           }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/LayoutVisitor.kt

@@ -11,7 +11,7 @@ import android.view.View
 import android.view.ViewGroup
 
 /** Layout Visitor traverses the entire view hierarchy from a given root. */
-class LayoutVisitor(val visitor: Visitor) {
+class LayoutVisitor(private val visitor: Visitor) {
   interface Visitor {
     fun visit(view: View)
   }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/core/RootViewResolver.kt

@@ -13,7 +13,6 @@ import android.view.WindowManager
 import java.lang.reflect.Field
 import java.lang.reflect.InvocationTargetException
 import java.lang.reflect.Modifier
-import java.util.ArrayList
 
 /**
  * Provides access to all root views in an application.
@@ -125,21 +124,23 @@ class RootViewResolver {
     var params: List<WindowManager.LayoutParams>? = null
     try {
       viewsField?.let { field ->
-        if (Build.VERSION.SDK_INT < 19) {
+        views =
-          val arr = field[windowManagerObj] as Array<View>
+            if (Build.VERSION.SDK_INT < 19) {
-          views = arr.toList()
+              val arr = field[windowManagerObj] as Array<View>
-        } else {
+              arr.toList()
-          views = field[windowManagerObj] as List<View>
+            } else {
-        }
+              field[windowManagerObj] as List<View>
+            }
       }
 
       paramsField?.let { field ->
-        if (Build.VERSION.SDK_INT < 19) {
+        params =
-          val arr = field[windowManagerObj] as Array<WindowManager.LayoutParams>
+            if (Build.VERSION.SDK_INT < 19) {
-          params = arr.toList() as List<WindowManager.LayoutParams>
+              val arr = field[windowManagerObj] as Array<WindowManager.LayoutParams>
-        } else {
+              arr.toList() as List<WindowManager.LayoutParams>
-          params = field[windowManagerObj] as List<WindowManager.LayoutParams>
+            } else {
-        }
+              field[windowManagerObj] as List<WindowManager.LayoutParams>
+            }
       }
     } catch (re: RuntimeException) {
       return null
@@ -150,12 +151,12 @@ class RootViewResolver {
     val roots = mutableListOf<RootView>()
     views?.let { views ->
       params?.let { params ->
-        for (i in views.indices) {
+        if (views.size == params.size) {
-          val view = views[i]
+          for (i in views.indices) {
-          // TODO  FIX, len(param) is not always the same as len(views) For now just use first
+            val view = views[i]
-
+            val param = params[i]
-          // params
+            roots.add(RootView(view, param))
-          roots.add(RootView(view, null))
+          }
         }
       }
     }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ActivityDescriptor.kt

@@ -9,7 +9,7 @@ package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import android.app.Activity
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
-import com.facebook.flipper.plugins.uidebugger.stetho.FragmentCompat
+import com.facebook.flipper.plugins.uidebugger.core.FragmentTracker
 
 object ActivityDescriptor : ChainedDescriptor<Activity>() {
 
@@ -24,30 +24,12 @@ object ActivityDescriptor : ChainedDescriptor<Activity>() {
   override fun onGetChildren(node: Activity, children: MutableList<Any>) {
     node.window?.let { window -> children.add(window) }
 
-    var fragments = getDialogFragments(FragmentCompat.supportInstance, node)
+    val fragments = FragmentTracker.getDialogFragments(node)
-    for (fragment in fragments) {
+    fragments.forEach { fragment -> children.add(fragment) }
-      children.add(fragment)
-    }
-
-    fragments = getDialogFragments(FragmentCompat.frameworkInstance, node)
-    for (fragment in fragments) {
-      children.add(fragment)
-    }
   }
 
   override fun onGetData(
       node: Activity,
       attributeSections: MutableMap<String, InspectableObject>
   ) {}
-
-  private fun getDialogFragments(
-      compat: FragmentCompat<*, *, *, *>?,
-      activity: Activity
-  ): List<Any> {
-    if (compat == null) {
-      return emptyList()
-    }
-
-    return compat.getDialogFragments(activity)
-  }
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ApplicationRefDescriptor.kt

@@ -8,14 +8,11 @@
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
 import android.app.Activity
-import android.util.Log
+import android.view.View
-import com.facebook.flipper.plugins.uidebugger.LogTag
 import com.facebook.flipper.plugins.uidebugger.core.ApplicationRef
-import com.facebook.flipper.plugins.uidebugger.core.RootViewResolver
 
 object ApplicationRefDescriptor : ChainedDescriptor<ApplicationRef>() {
 
-  val rootsLocal = RootViewResolver()
   override fun onGetActiveChild(node: ApplicationRef): Any? {
     return if (node.activitiesStack.isNotEmpty()) node.activitiesStack.last() else null
   }
@@ -34,27 +31,17 @@ object ApplicationRefDescriptor : ChainedDescriptor<ApplicationRef>() {
   override fun onGetChildren(node: ApplicationRef, children: MutableList<Any>) {
     val activeRoots = node.rootViews
 
-    Log.i(LogTag, rootsLocal.toString())
+    val added = mutableSetOf<View>()
-    activeRoots.let { roots ->
+    for (activity: Activity in node.activitiesStack) {
-      for (root in roots) {
+      children.add(activity)
-        var added = false
+      added.add(activity.window.decorView)
-        /**
+    }
-         * This code serves 2 purposes: 1.it picks up root views not tied to an activity (dialogs)
+
-         * 2. We can get initialized late and miss the first activity, it does seem that the root
+    // Picks up root views not tied to an activity (dialogs)
-         * view resolver is able to (usually ) get the root view regardless, with this we insert the
+    for (root in activeRoots) {
-         * root decor view without the activity. Ideally we wouldn't rely on this behaviour and find
+      if (!added.contains(root)) {
-         * a better way to track activities
+        children.add(root)
-         */
+        added.add(root)
-        for (activity: Activity in node.activitiesStack) {
-          if (activity.window.decorView == root) {
-            children.add(activity)
-            added = true
-            break
-          }
-        }
-        if (!added) {
-          children.add(root)
-        }
       }
     }
   }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/DescriptorRegister.kt

@@ -33,17 +33,22 @@ class DescriptorRegister {
       mapping.register(TextView::class.java, TextViewDescriptor)
       mapping.register(Button::class.java, ButtonDescriptor)
       mapping.register(ViewPager::class.java, ViewPagerDescriptor)
+      mapping.register(android.app.Fragment::class.java, FragmentFrameworkDescriptor)
+      mapping.register(androidx.fragment.app.Fragment::class.java, FragmentSupportDescriptor)
 
+      @Suppress("UNCHECKED_CAST")
       for (clazz in mapping.register.keys) {
-        val descriptor: NodeDescriptor<*>? = mapping.register[clazz]
+        val maybeDescriptor: NodeDescriptor<*>? = mapping.register[clazz]
-        descriptor?.let { descriptor ->
+        maybeDescriptor?.let { descriptor ->
           if (descriptor is ChainedDescriptor<*>) {
             val chainedDescriptor = descriptor as ChainedDescriptor<Any>
-            val superClass: Class<*> = clazz.getSuperclass()
+            val superClass: Class<*> = clazz.superclass
-            val superDescriptor: NodeDescriptor<*>? = mapping.descriptorForClass(superClass)
+            val maybeSuperDescriptor: NodeDescriptor<*>? = mapping.descriptorForClass(superClass)
-            // todo we should walk all the way up the superclass hierarchy?
+
-            if (superDescriptor is ChainedDescriptor<*>) {
+            maybeSuperDescriptor?.let { superDescriptor ->
-              chainedDescriptor.setSuper(superDescriptor as ChainedDescriptor<Any>)
+              if (superDescriptor is ChainedDescriptor<*>) {
+                chainedDescriptor.setSuper(superDescriptor as ChainedDescriptor<Any>)
+              }
             }
           }
         }
@@ -58,11 +63,17 @@ class DescriptorRegister {
   }
 
   fun <T> descriptorForClass(clazz: Class<T>): NodeDescriptor<T>? {
-    var clazz: Class<*> = clazz
+    var mutableClass: Class<*> = clazz
-    while (!register.containsKey(clazz)) {
+    while (!register.containsKey(mutableClass)) {
-      clazz = clazz.superclass
+      mutableClass = mutableClass.superclass
+    }
+
+    return if (register[clazz] != null) {
+      @Suppress("UNCHECKED_CAST")
+      register[clazz] as NodeDescriptor<T>
+    } else {
+      null
     }
-    return register[clazz] as NodeDescriptor<T>
   }
 
   fun <T> descriptorForClassUnsafe(clazz: Class<T>): NodeDescriptor<T> {

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/FragmentFrameworkDescriptor.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.descriptors
+
+import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
+
+object FragmentFrameworkDescriptor : ChainedDescriptor<android.app.Fragment>() {
+
+  override fun onGetId(node: android.app.Fragment): String {
+    return System.identityHashCode(node).toString()
+  }
+
+  override fun onGetName(node: android.app.Fragment): String {
+    return node.javaClass.simpleName
+  }
+
+  override fun onGetChildren(node: android.app.Fragment, children: MutableList<Any>) {
+    node.view?.let { view -> children.add(view) }
+  }
+
+  override fun onGetData(
+      node: android.app.Fragment,
+      attributeSections: MutableMap<String, InspectableObject>
+  ) {}
+}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/FragmentSupportDescriptor.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.flipper.plugins.uidebugger.descriptors
+
+import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
+
+object FragmentSupportDescriptor : ChainedDescriptor<androidx.fragment.app.Fragment>() {
+
+  override fun onGetId(node: androidx.fragment.app.Fragment): String {
+    return System.identityHashCode(node).toString()
+  }
+
+  override fun onGetName(node: androidx.fragment.app.Fragment): String {
+    return node.javaClass.simpleName
+  }
+
+  override fun onGetChildren(node: androidx.fragment.app.Fragment, children: MutableList<Any>) {
+    node.view?.let { view -> children.add(view) }
+  }
+
+  override fun onGetData(
+      node: androidx.fragment.app.Fragment,
+      attributeSections: MutableMap<String, InspectableObject>
+  ) {}
+}

android/src/main/java/com/facebook/flipper/plugins/uidebugger/descriptors/ViewGroupDescriptor.kt

@@ -7,7 +7,6 @@
 
 package com.facebook.flipper.plugins.uidebugger.descriptors
 
-import android.app.Fragment
 import android.os.Build
 import android.view.View
 import android.view.ViewGroup
@@ -16,7 +15,7 @@ import com.facebook.flipper.plugins.uidebugger.common.EnumMapping
 import com.facebook.flipper.plugins.uidebugger.common.Inspectable
 import com.facebook.flipper.plugins.uidebugger.common.InspectableObject
 import com.facebook.flipper.plugins.uidebugger.common.InspectableValue
-import com.facebook.flipper.plugins.uidebugger.stetho.FragmentCompat
+import com.facebook.flipper.plugins.uidebugger.core.FragmentTracker
 
 object ViewGroupDescriptor : ChainedDescriptor<ViewGroup>() {
 
@@ -32,8 +31,8 @@ object ViewGroupDescriptor : ChainedDescriptor<ViewGroup>() {
     val count = node.childCount - 1
     for (i in 0..count) {
       val child: View = node.getChildAt(i)
-      val fragment = getAttachedFragmentForView(child)
+      val fragment = FragmentTracker.getFragment(child)
-      if (fragment != null && !FragmentCompat.isDialogFragment(fragment)) {
+      if (fragment != null) {
         children.add(fragment)
       } else children.add(child)
     }
@@ -63,19 +62,4 @@ object ViewGroupDescriptor : ChainedDescriptor<ViewGroup>() {
                   "LAYOUT_MODE_CLIP_BOUNDS" to ViewGroupCompat.LAYOUT_MODE_CLIP_BOUNDS,
                   "LAYOUT_MODE_OPTICAL_BOUNDS" to ViewGroupCompat.LAYOUT_MODE_OPTICAL_BOUNDS,
               )) {}
-
-  private fun getAttachedFragmentForView(v: View): Any? {
-    return try {
-      val fragment = FragmentCompat.findFragmentForView(v)
-      var added = false
-      if (fragment is Fragment) {
-        added = fragment.isAdded
-      } else if (fragment is androidx.fragment.app.Fragment) {
-        added = fragment.isAdded
-      }
-      if (added) fragment else null
-    } catch (e: RuntimeException) {
-      null
-    }
-  }
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/ApplicationTreeObserver.kt

@@ -10,13 +10,12 @@ package com.facebook.flipper.plugins.uidebugger.observers
 import android.util.Log
 import android.view.View
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.TreeObserver
 import com.facebook.flipper.plugins.uidebugger.core.ApplicationRef
 import com.facebook.flipper.plugins.uidebugger.core.Context
 import com.facebook.flipper.plugins.uidebugger.core.RootViewResolver
 
 /**
- * responsible for observing the activity stack and managing the subscription to the top most
+ * Responsible for observing the activity stack and managing the subscription to the top most
  * content view (decor view)
  */
 class ApplicationTreeObserver(val context: Context) : TreeObserver<ApplicationRef>() {
@@ -48,6 +47,7 @@ class ApplicationTreeObserver(val context: Context) : TreeObserver<ApplicationRe
   }
 
   override fun unsubscribe() {
-    context.applicationRef.setActivityStackChangedListener(null)
+    // Not entirely sure this will ever happen or be needed.
+    // context.applicationRef.setActivityStackChangedListener(null)
   }
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/DecorViewTreeObserver.kt

@@ -11,7 +11,6 @@ import android.util.Log
 import android.view.View
 import android.view.ViewTreeObserver
 import com.facebook.flipper.plugins.uidebugger.LogTag
-import com.facebook.flipper.plugins.uidebugger.TreeObserver
 import com.facebook.flipper.plugins.uidebugger.core.Context
 
 typealias DecorView = View

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/ObserverFactory.kt

@@ -7,11 +7,9 @@
 
 package com.facebook.flipper.plugins.uidebugger.observers
 
-import com.facebook.flipper.plugins.uidebugger.TreeObserver
 import com.facebook.flipper.plugins.uidebugger.core.Context
 
 interface TreeObserverBuilder<T> {
-
   fun canBuildFor(node: Any): Boolean
   fun build(context: Context): TreeObserver<T>
 }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/TreeObserver.kt

@@ -5,11 +5,11 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-package com.facebook.flipper.plugins.uidebugger
+package com.facebook.flipper.plugins.uidebugger.observers
 
 import android.util.Log
+import com.facebook.flipper.plugins.uidebugger.LogTag
 import com.facebook.flipper.plugins.uidebugger.core.Context
-import com.facebook.flipper.plugins.uidebugger.observers.SubtreeUpdate
 
 /*
 Stateful class that manages some subtree in the UI Hierarchy.
@@ -75,7 +75,7 @@ abstract class TreeObserver<T> {
   }
 
   fun cleanUpRecursive() {
-    Log.i(LogTag, "Cleaning up observer ${this}")
+    Log.i(LogTag, "Cleaning up observer $this")
     children.values.forEach { it.cleanUpRecursive() }
     unsubscribe()
     children.clear()

android/src/main/java/com/facebook/flipper/plugins/uidebugger/stetho/AccessibilityUtil.kt

@@ -44,7 +44,7 @@ object AccessibilityUtil {
    * @param node The [AccessibilityNodeInfoCompat] to evaluate
    * @return `true` if it meets the criterion for producing spoken feedback
    */
-  fun isSpeakingNode(node: AccessibilityNodeInfoCompat?, view: View?): Boolean {
+  private fun isSpeakingNode(node: AccessibilityNodeInfoCompat?, view: View?): Boolean {
     if (node == null || view == null) {
       return false
     }
@@ -69,7 +69,7 @@ object AccessibilityUtil {
    * @param node The [AccessibilityNodeInfoCompat] to evaluate
    * @return `true` if it has any non-actionable speaking descendants within its subtree
    */
-  fun hasNonActionableSpeakingDescendants(
+  private fun hasNonActionableSpeakingDescendants(
       node: AccessibilityNodeInfoCompat?,
       view: View?
   ): Boolean {
@@ -79,10 +79,7 @@ object AccessibilityUtil {
     val viewGroup = view as ViewGroup
     val count = viewGroup.childCount - 1
     for (i in 0..count) {
-      val childView = viewGroup.getChildAt(i)
+      val childView = viewGroup.getChildAt(i) ?: continue
-      if (childView == null) {
-        continue
-      }
       val childNode = AccessibilityNodeInfoCompat.obtain()
       try {
         ViewCompat.onInitializeAccessibilityNodeInfo(childView, childNode)
@@ -107,7 +104,7 @@ object AccessibilityUtil {
    * @param node The [AccessibilityNodeInfoCompat] to evaluate
    * @return `true` if it is possible to gain accessibility focus
    */
-  fun isAccessibilityFocusable(node: AccessibilityNodeInfoCompat?, view: View?): Boolean {
+  private fun isAccessibilityFocusable(node: AccessibilityNodeInfoCompat?, view: View?): Boolean {
     if (node == null || view == null) {
       return false
     }

android/src/main/java/com/facebook/flipper/plugins/uidebugger/stetho/FragmentCompat.kt

@@ -47,6 +47,7 @@ abstract class FragmentCompat<
         }
         return field
       }
+
     private var hasSupportFragment = false
     init {
       hasSupportFragment = tryGetClassForName("androidx.fragment.app.Fragment") != null

android/src/main/java/com/facebook/flipper/plugins/uidebugger/stetho/FragmentCompatFramework.kt

@@ -56,7 +56,7 @@ class FragmentCompatFramework :
   }
 
   override fun forFragmentManager():
-      FragmentManagerAccessorViaReflection<FragmentManager, Fragment>? {
+      FragmentManagerAccessorViaReflection<FragmentManager, Fragment> {
     return fragmentManagerAccessor
   }
 
@@ -75,7 +75,7 @@ class FragmentCompatFramework :
     val fragmentManagerAccessor = forFragmentManager()
     var addedFragments: List<Any?>? = null
     try {
-      addedFragments = fragmentManagerAccessor?.getAddedFragments(fragmentManager)
+      addedFragments = fragmentManagerAccessor.getAddedFragments(fragmentManager)
     } catch (e: Exception) {}
 
     if (addedFragments != null) {
@@ -99,7 +99,7 @@ class FragmentCompatFramework :
     }
 
     val activityAccessor = forFragmentActivity()
-    val fragmentManager = activityAccessor?.getFragmentManager(activity) ?: return null
+    val fragmentManager = activityAccessor.getFragmentManager(activity) ?: return null
 
     return findFragmentForViewInFragmentManager(fragmentManager, view)
   }
@@ -111,7 +111,7 @@ class FragmentCompatFramework :
     val fragmentManagerAccessor = forFragmentManager()
     var fragments: List<Any>? = null
     try {
-      fragments = fragmentManagerAccessor?.getAddedFragments(fragmentManager)
+      fragments = fragmentManagerAccessor.getAddedFragments(fragmentManager)
     } catch (e: Exception) {}
 
     if (fragments != null) {

android/src/main/java/com/facebook/flipper/plugins/uidebugger/stetho/FragmentCompatSupportLib.kt

@@ -25,19 +25,19 @@ class FragmentCompatSupportLib :
   override val fragmentActivityClass: Class<FragmentActivity>
     get() = FragmentActivity::class.java
 
-  override fun forFragment(): FragmentAccessorSupportLib? {
+  override fun forFragment(): FragmentAccessorSupportLib {
     return fragmentAccessor
   }
 
-  override fun forDialogFragment(): DialogFragmentAccessorSupportLib? {
+  override fun forDialogFragment(): DialogFragmentAccessorSupportLib {
     return dialogFragmentAccessor
   }
 
-  override fun forFragmentManager(): FragmentManagerAccessor<FragmentManager, Fragment>? {
+  override fun forFragmentManager(): FragmentManagerAccessor<FragmentManager, Fragment> {
     return fragmentManagerAccessor
   }
 
-  override fun forFragmentActivity(): FragmentActivityAccessorSupportLib? {
+  override fun forFragmentActivity(): FragmentActivityAccessorSupportLib {
     return fragmentActivityAccessor
   }
 
@@ -48,12 +48,12 @@ class FragmentCompatSupportLib :
 
     val activityAccessor = forFragmentActivity()
     val fragmentManager =
-        activityAccessor?.getFragmentManager(activity as FragmentActivity) ?: return emptyList()
+        activityAccessor.getFragmentManager(activity as FragmentActivity) ?: return emptyList()
 
     val fragmentManagerAccessor = forFragmentManager()
     var addedFragments: List<Any?>? = null
     try {
-      addedFragments = fragmentManagerAccessor?.getAddedFragments(fragmentManager)
+      addedFragments = fragmentManagerAccessor.getAddedFragments(fragmentManager)
     } catch (e: Exception) {}
 
     if (addedFragments != null) {
@@ -78,7 +78,7 @@ class FragmentCompatSupportLib :
 
     val activityAccessor = forFragmentActivity()
     val fragmentManager =
-        activityAccessor?.getFragmentManager(activity as FragmentActivity) ?: return null
+        activityAccessor.getFragmentManager(activity as FragmentActivity) ?: return null
 
     return findFragmentForViewInFragmentManager(fragmentManager, view)
   }
@@ -90,7 +90,7 @@ class FragmentCompatSupportLib :
     val fragmentManagerAccessor = forFragmentManager()
     var fragments: List<Any>? = null
     try {
-      fragments = fragmentManagerAccessor?.getAddedFragments(fragmentManager)
+      fragments = fragmentManagerAccessor.getAddedFragments(fragmentManager)
     } catch (e: Exception) {}
 
     if (fragments != null) {
@@ -112,17 +112,13 @@ class FragmentCompatSupportLib :
     }
 
     val fragmentAccessor = forFragment()
-    fragmentAccessor?.let { accessor ->
+    if (fragmentAccessor.getView(fragment as Fragment) === view) {
-      if (accessor.getView(fragment as Fragment) === view) {
+      return fragment
-        return fragment
-      }
-      val childFragmentManager = accessor.getChildFragmentManager(fragment as Fragment)
-      return if (childFragmentManager != null) {
-        findFragmentForViewInFragmentManager(childFragmentManager, view)
-      } else null
     }
-
+    val childFragmentManager = fragmentAccessor.getChildFragmentManager(fragment as Fragment)
-    return null
+    return if (childFragmentManager != null) {
+      findFragmentForViewInFragmentManager(childFragmentManager, view)
+    } else null
   }
 
   open class FragmentAccessorSupportLib : FragmentAccessor<Fragment, FragmentManager> {
@@ -161,7 +157,7 @@ class FragmentCompatSupportLib :
 
   class FragmentActivityAccessorSupportLib :
       FragmentActivityAccessor<FragmentActivity, FragmentManager> {
-    override fun getFragmentManager(activity: FragmentActivity): FragmentManager? {
+    override fun getFragmentManager(activity: FragmentActivity): FragmentManager {
       return activity.supportFragmentManager
     }
   }