refactor: move most of the preferences activity into a fragment

AnkiDroid/src/main/AndroidManifest.xml

@@ -346,7 +346,7 @@
             android:configChanges="orientation|screenSize"
             android:exported="false" />
         <activity
-            android:name="com.ichi2.anki.preferences.Preferences"
+            android:name="com.ichi2.anki.preferences.PreferencesActivity"
             android:exported="false"
             android:configChanges="screenSize"
             >

AnkiDroid/src/main/java/com/ichi2/anki/CollectionHelper.kt

@@ -25,7 +25,6 @@ import androidx.core.content.edit
 import com.ichi2.anki.AnkiDroidFolder.AppPrivateFolder
 import com.ichi2.anki.exception.StorageAccessException
 import com.ichi2.anki.exception.UnknownDatabaseVersionException
-import com.ichi2.anki.preferences.Preferences
 import com.ichi2.anki.preferences.sharedPrefs
 import com.ichi2.libanki.Collection
 import com.ichi2.libanki.DB
@@ -47,7 +46,7 @@ object CollectionHelper {
      * This directory contains all AnkiDroid data and media for a given collection
      * Except the Android preferences, cached files and [MetaDB]
      *
-     * This can be changed by the [Preferences] screen
+     * This can be changed by the Preferences screen
      * to allow a user to access a second collection via the same AnkiDroid app instance.
      *
      * The path also defines the collection that the AnkiDroid API accesses

AnkiDroid/src/main/java/com/ichi2/anki/DeckPicker.kt

@@ -141,6 +141,7 @@ import com.ichi2.anki.pages.AnkiPackageImporterFragment
 import com.ichi2.anki.pages.CongratsPage
 import com.ichi2.anki.pages.CongratsPage.Companion.onDeckCompleted
 import com.ichi2.anki.preferences.AdvancedSettingsFragment
+import com.ichi2.anki.preferences.PreferencesActivity
 import com.ichi2.anki.preferences.sharedPrefs
 import com.ichi2.anki.receiver.SdCardReceiver
 import com.ichi2.anki.servicelayer.ScopedStorageService
@@ -788,7 +789,7 @@ open class DeckPicker :
                 convertDpToPixel(32F, this@DeckPicker).toInt()
             )
             positiveButton(R.string.open_settings) {
-                val settingsIntent = AdvancedSettingsFragment.getSubscreenIntent(this@DeckPicker)
+                val settingsIntent = PreferencesActivity.getIntent(this@DeckPicker, AdvancedSettingsFragment::class)
                 requestPathUpdateLauncher.launch(settingsIntent)
             }
         }

AnkiDroid/src/main/java/com/ichi2/anki/NavigationDrawerActivity.kt

@@ -41,7 +41,7 @@ import androidx.drawerlayout.widget.DrawerLayout
 import com.google.android.material.color.MaterialColors
 import com.google.android.material.navigation.NavigationView
 import com.ichi2.anki.dialogs.help.HelpDialog
-import com.ichi2.anki.preferences.Preferences
+import com.ichi2.anki.preferences.PreferencesActivity
 import com.ichi2.anki.preferences.sharedPrefs
 import com.ichi2.anki.workarounds.FullDraggableContainerFix
 import com.ichi2.compat.CompatHelper
@@ -357,10 +357,9 @@ abstract class NavigationDrawerActivity :
 
     /**
      * Opens AnkiDroid's Settings Screen.
-     * @see Preferences
      */
     protected fun openSettings() {
-        val intent = Intent(this, Preferences::class.java)
+        val intent = PreferencesActivity.getIntent(this)
         preferencesLauncher.launch(intent)
     }
 

AnkiDroid/src/main/java/com/ichi2/anki/preferences/AdvancedSettingsFragment.kt

@@ -16,7 +16,6 @@
 package com.ichi2.anki.preferences
 
 import android.content.ComponentName
-import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
 import androidx.appcompat.app.AlertDialog
@@ -142,10 +141,4 @@ class AdvancedSettingsFragment : SettingsFragment() {
             }
         }
     }
-
-    companion object {
-        fun getSubscreenIntent(context: Context): Intent {
-            return getSubscreenIntent(context, AdvancedSettingsFragment::class)
-        }
-    }
 }

AnkiDroid/src/main/java/com/ichi2/anki/preferences/CustomButtonsSettingsFragment.kt

@@ -15,8 +15,6 @@
  */
 package com.ichi2.anki.preferences
 
-import android.content.Context
-import android.content.Intent
 import androidx.annotation.VisibleForTesting
 import androidx.appcompat.app.AlertDialog
 import androidx.core.content.edit
@@ -59,10 +57,4 @@ class CustomButtonsSettingsFragment : SettingsFragment() {
     fun allKeys(): HashSet<String> {
         return allPreferences().mapTo(hashSetOf()) { it.key }
     }
-
-    companion object {
-        fun getSubscreenIntent(context: Context): Intent {
-            return getSubscreenIntent(context, CustomButtonsSettingsFragment::class)
-        }
-    }
 }

AnkiDroid/src/main/java/com/ichi2/anki/preferences/Preferences.kt

@@ -19,80 +19,73 @@
  ****************************************************************************************/
 package com.ichi2.anki.preferences
 
+import android.content.Context
+import android.content.Intent
 import android.os.Bundle
-import android.view.MenuItem
+import android.view.View
+import androidx.activity.OnBackPressedCallback
 import androidx.annotation.XmlRes
+import androidx.core.os.bundleOf
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.commit
 import androidx.preference.Preference
 import androidx.preference.PreferenceFragmentCompat
+import com.bytehamster.lib.preferencesearch.SearchConfiguration
 import com.bytehamster.lib.preferencesearch.SearchPreferenceResult
 import com.bytehamster.lib.preferencesearch.SearchPreferenceResultListener
 import com.google.android.material.appbar.AppBarLayout
 import com.google.android.material.appbar.CollapsingToolbarLayout
-import com.ichi2.anki.AnkiActivity
+import com.google.android.material.appbar.MaterialToolbar
 import com.ichi2.anki.R
+import com.ichi2.anki.SingleFragmentActivity
 import com.ichi2.anki.utils.isWindowCompact
-import com.ichi2.themes.setTransparentStatusBar
 import com.ichi2.utils.getInstanceFromClassName
 import timber.log.Timber
+import kotlin.reflect.KClass
 import kotlin.reflect.jvm.jvmName
 
-class Preferences :
-    AnkiActivity(),
+class PreferencesFragment :
+    Fragment(R.layout.preferences),
     PreferenceFragmentCompat.OnPreferenceStartFragmentCallback,
     SearchPreferenceResultListener {
 
-    override fun onCreate(savedInstanceState: Bundle?) {
-        super.onCreate(savedInstanceState)
-        setContentView(R.layout.preferences)
-        setTransparentStatusBar()
-
-        enableToolbar().setDisplayHomeAsUpEnabled(true)
-
-        // Load initial fragment if activity is being first created
-        if (savedInstanceState == null) {
-            loadInitialFragment()
-        }
-        supportFragmentManager.addOnBackStackChangedListener {
-            // Expand bar in new fragments if scrolled to top
-            val fragment = supportFragmentManager.findFragmentById(R.id.settings_container)
-                as? PreferenceFragmentCompat ?: return@addOnBackStackChangedListener
-            fragment.listView.post {
-                val viewHolder = fragment.listView?.findViewHolderForAdapterPosition(0)
-                val isAtTop = viewHolder != null && viewHolder.itemView.top >= 0
-                findViewById<AppBarLayout>(R.id.appbar).setExpanded(isAtTop, false)
+    private val onBackPressedCallback = object : OnBackPressedCallback(true) {
+        override fun handleOnBackPressed() {
+            if (childFragmentManager.backStackEntryCount > 0) {
+                childFragmentManager.popBackStack()
+            } else {
+                requireActivity().finish()
             }
-
-            val title = if (fragment is TitleProvider) fragment.title else ""
-            findViewById<CollapsingToolbarLayout>(R.id.collapsingToolbarLayout)?.title = title
-            supportActionBar?.title = title
         }
     }
 
-    /**
-     * Starts the first fragment for the [Preferences] activity,
-     * which by default is [HeaderFragment].
-     * The initial fragment may be overridden by putting the java class name
-     * of the fragment on an intent extra with the key [INITIAL_FRAGMENT_EXTRA]
-     */
-    private fun loadInitialFragment() {
-        val fragmentClassName = intent?.getStringExtra(INITIAL_FRAGMENT_EXTRA)
-        val initialFragment = if (fragmentClassName == null) {
-            if (resources.isWindowCompact()) HeaderFragment() else GeneralSettingsFragment()
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        view.findViewById<MaterialToolbar>(R.id.toolbar)
+            .setNavigationOnClickListener { onBackPressedCallback.handleOnBackPressed() }
+
+        requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner, onBackPressedCallback)
+
+        // Load initial subscreen if activity is being first created
+        if (savedInstanceState == null) {
+            loadInitialSubscreen()
         } else {
-            try {
-                getInstanceFromClassName<Fragment>(fragmentClassName)
-            } catch (e: Exception) {
-                throw RuntimeException("Failed to load $fragmentClassName", e)
+            childFragmentManager.findFragmentById(R.id.settings_container)?.let {
+                setFragmentTitleOnToolbar(it)
             }
         }
-        supportFragmentManager.commit {
-            // In tablets, show the headers fragment at the lateral navigation container
-            if (!resources.isWindowCompact()) {
-                replace(R.id.lateral_nav_container, HeaderFragment())
+
+        childFragmentManager.addOnBackStackChangedListener {
+            val fragment = childFragmentManager.findFragmentById(R.id.settings_container)
+                ?: return@addOnBackStackChangedListener
+
+            setFragmentTitleOnToolbar(fragment)
+
+            // Expand bar in new fragments if scrolled to top
+            (fragment as? PreferenceFragmentCompat)?.listView?.post {
+                val viewHolder = fragment.listView?.findViewHolderForAdapterPosition(0)
+                val isAtTop = viewHolder != null && viewHolder.itemView.top >= 0
+                view.findViewById<AppBarLayout>(R.id.appbar).setExpanded(isAtTop, false)
             }
-            replace(R.id.settings_container, initialFragment, initialFragment::class.java.name)
         }
     }
 
@@ -101,49 +94,91 @@ class Preferences :
         pref: Preference
     ): Boolean {
         // avoid reopening the same fragment if already active
-        val currentFragment = supportFragmentManager.findFragmentById(R.id.settings_container)
+        val currentFragment = childFragmentManager.findFragmentById(R.id.settings_container)
             ?: return true
         if (pref.fragment == currentFragment::class.jvmName) return true
 
-        val fragment = supportFragmentManager.fragmentFactory.instantiate(
-            classLoader,
+        val fragment = childFragmentManager.fragmentFactory.instantiate(
+            requireActivity().classLoader,
             pref.fragment ?: return true
         )
         fragment.arguments = pref.extras
-        supportFragmentManager.commit {
+        childFragmentManager.commit {
             replace(R.id.settings_container, fragment, fragment::class.jvmName)
             addToBackStack(null)
         }
         return true
     }
 
-    override fun onOptionsItemSelected(item: MenuItem): Boolean {
-        if (item.itemId == android.R.id.home) {
-            if (resources.isWindowCompact()) {
-                onBackPressedDispatcher.onBackPressed()
-            } else {
-                finish()
-            }
-        }
-        return true
-    }
-
-    // ----------------------------------------------------------------------------
-    // Class methods
-    // ----------------------------------------------------------------------------
-
     override fun onSearchResultClicked(result: SearchPreferenceResult) {
         val fragment = getFragmentFromXmlRes(result.resourceFile) ?: return
 
-        supportFragmentManager.popBackStack() // clear the search fragment from the backstack
-        supportFragmentManager.commit {
+        parentFragmentManager.popBackStack() // clear the search fragment from the backstack
+        childFragmentManager.commit {
             replace(R.id.settings_container, fragment, fragment.javaClass.name)
             addToBackStack(fragment.javaClass.name)
         }
 
         Timber.i("Highlighting key '%s' on %s", result.key, fragment)
         result.highlight(fragment as PreferenceFragmentCompat)
     }
+
+    private fun setFragmentTitleOnToolbar(fragment: Fragment) {
+        val title = if (fragment is TitleProvider) fragment.title else getString(R.string.settings)
+
+        view?.findViewById<CollapsingToolbarLayout>(R.id.collapsingToolbarLayout)?.title = title
+        view?.findViewById<MaterialToolbar>(R.id.toolbar)?.title = title
+    }
+
+    /**
+     * Starts the first settings fragment, which by default is [HeaderFragment].
+     * The initial fragment may be overridden by putting the java class name
+     * of the fragment on an intent extra with the key [INITIAL_FRAGMENT_EXTRA]
+     */
+    private fun loadInitialSubscreen() {
+        val fragmentClassName = arguments?.getString(INITIAL_FRAGMENT_EXTRA)
+        val initialFragment = if (fragmentClassName == null) {
+            if (resources.isWindowCompact()) HeaderFragment() else GeneralSettingsFragment()
+        } else {
+            try {
+                getInstanceFromClassName<Fragment>(fragmentClassName)
+            } catch (e: Exception) {
+                throw RuntimeException("Failed to load $fragmentClassName", e)
+            }
+        }
+        childFragmentManager.commit {
+            // In big screens, show the headers fragment at the lateral navigation container
+            if (!resources.isWindowCompact()) {
+                replace(R.id.lateral_nav_container, HeaderFragment())
+            }
+            replace(R.id.settings_container, initialFragment, initialFragment::class.java.name)
+        }
+    }
+}
+
+/**
+ * Host activity for [PreferencesFragment].
+ *
+ * Only necessary because [SearchConfiguration] demands an activity that implements
+ * [SearchPreferenceResultListener].
+ */
+class PreferencesActivity : SingleFragmentActivity(), SearchPreferenceResultListener {
+    override fun onSearchResultClicked(result: SearchPreferenceResult) {
+        val fragment = supportFragmentManager.findFragmentByTag(FRAGMENT_TAG)
+        if (fragment is SearchPreferenceResultListener) {
+            fragment.onSearchResultClicked(result)
+        }
+    }
+
+    companion object {
+        fun getIntent(context: Context, initialFragment: KClass<out SettingsFragment>? = null): Intent {
+            val arguments = bundleOf(INITIAL_FRAGMENT_EXTRA to initialFragment?.jvmName)
+            return Intent(context, PreferencesActivity::class.java).apply {
+                putExtra(FRAGMENT_NAME_EXTRA, PreferencesFragment::class.jvmName)
+                putExtra(FRAGMENT_ARGS_EXTRA, arguments)
+            }
+        }
+    }
 }
 
 interface TitleProvider {

AnkiDroid/src/main/java/com/ichi2/anki/preferences/SettingsFragment.kt

@@ -15,8 +15,6 @@
  */
 package com.ichi2.anki.preferences
 
-import android.content.Context
-import android.content.Intent
 import android.content.SharedPreferences
 import android.os.Bundle
 import androidx.annotation.VisibleForTesting
@@ -31,8 +29,6 @@ import com.ichi2.anki.analytics.UsageAnalytics
 import com.ichi2.preferences.DialogFragmentProvider
 import timber.log.Timber
 import java.lang.NumberFormatException
-import kotlin.reflect.KClass
-import kotlin.reflect.jvm.jvmName
 
 abstract class SettingsFragment :
     PreferenceFragmentCompat(),
@@ -132,12 +128,6 @@ abstract class SettingsFragment :
     }
 
     companion object {
-        @JvmStatic // Using protected members which are not @JvmStatic in the superclass companion is unsupported yet
-        protected fun getSubscreenIntent(context: Context, fragmentClass: KClass<out SettingsFragment>): Intent {
-            return Intent(context, Preferences::class.java)
-                .putExtra(INITIAL_FRAGMENT_EXTRA, fragmentClass.jvmName)
-        }
-
         /**
          * Converts a preference value to a numeric number that
          * can be reported to analytics, since analytics events only accept

AnkiDroid/src/main/res/layout/preferences.xml

@@ -22,7 +22,7 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:fitsSystemWindows="true"
-    tools:context=".preferences.Preferences">
+    tools:context=".preferences.PreferencesFragment">
 
     <com.google.android.material.appbar.AppBarLayout
         android:id="@+id/appbar"
@@ -45,7 +45,7 @@
                 app:layout_collapseMode="pin"
                 app:navigationContentDescription="@string/abc_action_bar_up_description"
                 app:navigationIcon="?attr/homeAsUpIndicator"
-                tools:title="@string/settings"/>
+                app:title="@string/settings"/>
 
         </com.google.android.material.appbar.CollapsingToolbarLayout>