Fix: Settings title stuck when backing out of sub-menus

.claude/.gitignore

@@ -1,3 +1,4 @@
 settings.local.json
 tmp/
 worktrees/
+scheduled_tasks.lock

app/src/main/java/eu/darken/sdmse/main/ui/settings/SettingsFragment.kt

@@ -1,9 +1,10 @@
 package eu.darken.sdmse.main.ui.settings
 
 import android.os.Bundle
-import android.os.Parcelable
 import android.view.View
 import androidx.appcompat.widget.Toolbar
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentManager
 import androidx.fragment.app.viewModels
 import androidx.preference.Preference
 import androidx.preference.PreferenceFragmentCompat
@@ -14,7 +15,6 @@ import eu.darken.sdmse.common.uix.Fragment2
 import eu.darken.sdmse.common.uix.ToolbarHost
 import eu.darken.sdmse.common.viewbinding.viewBinding
 import eu.darken.sdmse.databinding.SettingsFragmentBinding
-import kotlinx.parcelize.Parcelize
 
 @AndroidEntryPoint
 class SettingsFragment : Fragment2(R.layout.settings_fragment),
@@ -27,93 +27,67 @@ class SettingsFragment : Fragment2(R.layout.settings_fragment),
     override val toolbar: Toolbar
         get() = ui.toolbar
 
-    private val screens = ArrayList<Screen>()
-
-    @Parcelize
-    data class Screen(
-        val fragmentClass: String,
-        val screenTitle: String?,
-        val screenSubtitle: String? = null,
-    ) : Parcelable
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        // Drive the toolbar from fragment lifecycle + fragment arguments.
+        // We can't trust childFragmentManager.backStackEntryCount inside the resumed
+        // callback: on Android 16's predictive-back path, the new fragment becomes
+        // RESUMED before the back stack has actually been decremented, so reading
+        // the count here would give a stale value.
+        childFragmentManager.registerFragmentLifecycleCallbacks(
+            object : FragmentManager.FragmentLifecycleCallbacks() {
+                override fun onFragmentResumed(fm: FragmentManager, f: Fragment) {
+                    if (f.id == R.id.content_frame && view != null) {
+                        syncToolbarForFragment(f)
+                    }
+                }
+            },
+            false,
+        )
+    }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         EdgeToEdgeHelper(requireActivity()).apply {
             insetsPadding(ui.root, left = true, right = true)
             insetsPadding(ui.appbarlayout, top = true)
         }
 
-        childFragmentManager.addOnBackStackChangedListener {
-            val backStackCnt = childFragmentManager.backStackEntryCount
-            val newScreenInfo = when {
-                backStackCnt < screens.size -> {
-                    // We popped the backstack, restore the underlying screen infos
-                    // If there are none left, we are at the index again
-                    screens.removeLastOrNull()
-                    screens.lastOrNull() ?: Screen(
-                        fragmentClass = SettingsIndexFragment::class.qualifiedName!!,
-                        screenTitle = getString(eu.darken.sdmse.common.R.string.general_settings_title)
-                    )
-                }
-
-                else -> {
-                    // We added the current fragment to the stack, the new fragment's infos were already set, do nothing.
-                    null
-                }
-            }
-
-            newScreenInfo?.let { setCurrentScreenInfo(it) }
+        if (savedInstanceState == null
+            && childFragmentManager.findFragmentById(R.id.content_frame) == null
+        ) {
+            childFragmentManager
+                .beginTransaction()
+                .add(R.id.content_frame, SettingsIndexFragment())
+                .commit()
         }
 
-        if (savedInstanceState == null) {
-            val currentFragment = childFragmentManager.findFragmentById(R.id.content_frame)
-            if (currentFragment == null) {
-                childFragmentManager
-                    .beginTransaction()
-                    .add(R.id.content_frame, SettingsIndexFragment())
-                    .commit()
-            }
-        } else {
-            @Suppress("DEPRECATION")
-            savedInstanceState.getParcelableArrayList<Screen>(BKEY_SCREEN_INFOS)?.let {
-                screens.addAll(it)
-            }
-        }
-
-        // Always restore toolbar title from current screen state (handles NavComponent view recreation)
-        screens.lastOrNull()?.let { setCurrentScreenInfo(it) }
+        // Sync on first view creation AND on NavComponent view recreation.
+        childFragmentManager.findFragmentById(R.id.content_frame)?.let { syncToolbarForFragment(it) }
 
         ui.toolbar.setNavigationOnClickListener { requireActivity().onBackPressedDispatcher.onBackPressed() }
 
         super.onViewCreated(view, savedInstanceState)
     }
 
-    override fun onSaveInstanceState(outState: Bundle) {
-        super.onSaveInstanceState(outState)
-        outState.putParcelableArrayList(BKEY_SCREEN_INFOS, screens)
-    }
-
     override fun onPreferenceStartFragment(caller: PreferenceFragmentCompat, pref: Preference): Boolean {
-        val screenInfo = Screen(
-            fragmentClass = pref.fragment!!,
-            screenTitle = pref.title?.toString(),
-            screenSubtitle = ui.toolbar.title?.toString(),
-        )
-
-        val args = Bundle().apply {
-            putAll(pref.extras)
-            putString(BKEY_SCREEN_TITLE, screenInfo.screenTitle)
-        }
+        val title = pref.title?.toString().orEmpty()
 
         @Suppress("DEPRECATION")
         val fragment = childFragmentManager.fragmentFactory
             .instantiate(this::class.java.classLoader!!, pref.fragment!!)
             .apply {
-                arguments = args
+                arguments = Bundle().apply {
+                    putAll(pref.extras)
+                    putString(BKEY_SCREEN_TITLE, title)
+                }
                 setTargetFragment(caller, 0)
             }
 
-        setCurrentScreenInfo(screenInfo)
-        screens.add(screenInfo)
+        // Update toolbar synchronously before commit so the title matches the transition.
+        setToolbar(
+            title = title,
+            subtitle = getString(eu.darken.sdmse.common.R.string.general_settings_title),
+        )
 
         childFragmentManager.beginTransaction().apply {
             replace(R.id.content_frame, fragment)
@@ -123,16 +97,27 @@ class SettingsFragment : Fragment2(R.layout.settings_fragment),
         return true
     }
 
-
-    private fun setCurrentScreenInfo(info: Screen) {
-        ui.toolbar.apply {
-            title = info.screenTitle
-            subtitle = info.screenSubtitle
+    private fun syncToolbarForFragment(f: Fragment) {
+        val screenTitle = f.arguments?.getString(BKEY_SCREEN_TITLE)
+        if (screenTitle != null) {
+            setToolbar(
+                title = screenTitle,
+                subtitle = getString(eu.darken.sdmse.common.R.string.general_settings_title),
+            )
+        } else {
+            setToolbar(
+                title = getString(eu.darken.sdmse.common.R.string.general_settings_title),
+                subtitle = null,
+            )
         }
     }
 
+    private fun setToolbar(title: String?, subtitle: String?) {
+        ui.toolbar.title = title
+        ui.toolbar.subtitle = subtitle
+    }
+
     companion object {
         private const val BKEY_SCREEN_TITLE = "preferenceScreenTitle"
-        private const val BKEY_SCREEN_INFOS = "preferenceScreenInfos"
     }
 }