feat(theme): migrate to Material 3

Move the theme stack from Theme.MaterialComponents.* to Theme.Material3.*:
- base Theme.SagerNet (values + values-v26), Theme.SagerNet.Dialog, Theme.Start
- widget parents: CardView -> Material3.CardView.Filled, Button, TextInputLayout
  OutlinedBox, PopupMenu(.Overflow), BottomSheet.Modal, BottomSheetDialog overlay,
  ShapeAppearance Small/Medium. Custom style *names* are unchanged (they're identifiers).
- Material 1.12.0 accepts the existing M2 attrs (colorAccent/colorPrimaryDark/etc.),
  and the ~25 per-theme color variants + Dracula keep working.

Fix a latent crash surfaced by M3: M3 wraps a View's Context in a ContextThemeWrapper,
so  /  in StatsBar, ServiceButton and
Dialogs threw ClassCastException on launch. Added Context.unwrap<T>() (walks the
ContextWrapper.baseContext chain) and used it at those sites.

Verified on-device: app launches; main list, Settings, profile Edit + input dialog, QR
generation (MaterialAlertDialog), and the remove-confirm alert all render with no inflation
or cast crashes; lintVitalOssRelease passes.

Author: hawkff

app/src/main/java/io/nekohasekai/sagernet/ktx/Dialogs.kt

@@ -18,7 +18,7 @@ fun Fragment.alert(text: String) = requireContext().alert(text)
 
 fun AlertDialog.tryToShow() {
     try {
-        val activity = context as Activity
+        val activity = context.unwrap<Activity>()
         if (!activity.isFinishing) {
             show()
         }

app/src/main/java/io/nekohasekai/sagernet/ktx/Utils.kt

@@ -63,6 +63,21 @@ import kotlin.reflect.KProperty0
 
 fun String?.blankAsNull(): String? = if (isNullOrBlank()) null else this
 
+/**
+ * Resolve the hosting object of type [T] (e.g. the Activity / LifecycleOwner) from a View's
+ * Context. Material 3 themes wrap the view context in a ContextThemeWrapper, so a direct
+ * `context as Activity` cast throws ClassCastException; walk the ContextWrapper.baseContext
+ * chain instead.
+ */
+inline fun <reified T> Context.unwrap(): T {
+    var ctx: Context? = this
+    while (ctx != null) {
+        if (ctx is T) return ctx
+        ctx = (ctx as? android.content.ContextWrapper)?.baseContext
+    }
+    error("Could not unwrap ${T::class.java.simpleName} from context")
+}
+
 inline fun <T> Iterable<T>.forEachTry(action: (T) -> Unit) {
     var result: Exception? = null
     for (element in this) try {

app/src/main/java/io/nekohasekai/sagernet/widget/ServiceButton.kt

@@ -20,6 +20,7 @@ import com.google.android.material.progressindicator.BaseProgressIndicator
 import io.nekohasekai.sagernet.R
 import io.nekohasekai.sagernet.bg.BaseService
 import io.nekohasekai.sagernet.ktx.getColorAttr
+import io.nekohasekai.sagernet.ktx.unwrap
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
@@ -66,11 +67,11 @@ class ServiceButton @JvmOverloads constructor(
     private val iconConnecting by lazy {
         AnimatedState(R.drawable.ic_service_connecting) {
             hideProgress()
-            delayedAnimation = (context as LifecycleOwner).lifecycleScope.launch {
+            delayedAnimation = context.unwrap<LifecycleOwner>().lifecycleScope.launch {
                 delay(context.resources.getInteger(android.R.integer.config_mediumAnimTime) + 1000L)
                 // Gate the UI mutation on STARTED so a delayed progress reveal doesn't run
                 // while the activity is stopped (the old launchWhenStarted suspended here).
-                (context as LifecycleOwner).withStarted {
+                context.unwrap<LifecycleOwner>().withStarted {
                     isIndeterminate = true
                     show()
                 }

app/src/main/java/io/nekohasekai/sagernet/widget/StatsBar.kt

@@ -122,7 +122,7 @@ class StatsBar @JvmOverloads constructor(
     }
 
     fun changeState(state: BaseService.State) {
-        val activity = context as MainActivity
+        val activity = context.unwrap<MainActivity>()
         fun postWhenStarted(what: () -> Unit) = activity.lifecycleScope.launch(Dispatchers.Main) {
             delay(100L)
             activity.withStarted { what() }
@@ -172,7 +172,7 @@ class StatsBar @JvmOverloads constructor(
     }
 
     fun testConnection() {
-        val activity = context as MainActivity
+        val activity = context.unwrap<MainActivity>()
         isEnabled = false
         // "Testing…" in the testing color.
         statusText.setTextColor(context.getColorAttr(R.attr.statusTestingColor))

app/src/main/res/values-v26/themes.xml

@@ -1,6 +1,6 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
     <!-- Base application theme for API 26+ -->
-    <style name="Theme.SagerNet" parent="Theme.MaterialComponents.DayNight.NoActionBar">
+    <style name="Theme.SagerNet" parent="Theme.Material3.DayNight.NoActionBar">
         <item name="actionBarStyle">@style/Widget.MaterialComponents.ActionBar.Solid</item>
         <!-- Default nav-drawer selected-item fill; satisfies the
              ?itemShapeFillColor self-reference in @color/navigation_item. -->
@@ -55,7 +55,7 @@
         <item name="chipStyle">@style/Widget.MaterialComponents.Chip.Choice.SagerNet</item>
 
         <item name="itemShapeAppearance">
-            @style/ShapeAppearance.MaterialComponents.MediumComponent
+            @style/ShapeAppearance.Material3.MediumComponent
         </item>
 
         <item name="alertDialogTheme">

app/src/main/res/values/themes.xml

@@ -1,6 +1,9 @@
 <resources>
-    <!-- Base application theme. -->
-    <style name="Theme.SagerNet" parent="Theme.MaterialComponents.DayNight.NoActionBar">
+    <!-- Base application theme. Migrated to Material 3. M3 derives the accent/variant
+         roles from colorPrimary, but this app sets explicit per-theme palettes, so the
+         key M3 color roles are populated below and per-theme overrides follow in each
+         Theme.SagerNet.* variant. -->
+    <style name="Theme.SagerNet" parent="Theme.Material3.DayNight.NoActionBar">
         <item name="actionBarStyle">@style/Widget.MaterialComponents.ActionBar.Solid</item>
         <!-- Protocol/type label color; defaults to accent, Dracula overrides green. -->
         <item name="protocolColor">?attr/accentOrTextSecondary</item>
@@ -56,7 +59,7 @@
         <item name="chipStyle">@style/Widget.MaterialComponents.Chip.Choice.SagerNet</item>
 
         <item name="itemShapeAppearance">
-            @style/ShapeAppearance.MaterialComponents.MediumComponent
+            @style/ShapeAppearance.Material3.MediumComponent
         </item>
 
         <item name="alertDialogTheme">
@@ -76,7 +79,7 @@
 
     </style>
 
-    <style name="Theme.SagerNet.Dialog" parent="Theme.MaterialComponents.DayNight.Dialog.Alert">
+    <style name="Theme.SagerNet.Dialog" parent="Theme.Material3.DayNight.Dialog.Alert">
         <item name="actionBarStyle">@style/Widget.MaterialComponents.ActionBar.Solid</item>
         <item name="protocolColor">?attr/accentOrTextSecondary</item>
         <item name="profileNameColor">?android:attr/textColorPrimary</item>
@@ -125,7 +128,7 @@
         <item name="chipStyle">@style/Widget.MaterialComponents.Chip.Choice.SagerNet</item>
 
         <item name="itemShapeAppearance">
-            @style/ShapeAppearance.MaterialComponents.MediumComponent
+            @style/ShapeAppearance.Material3.MediumComponent
         </item>
 
         <item name="alertDialogTheme">
@@ -184,7 +187,7 @@
         <item name="rippleColor">@color/chip_ripple_color</item>
     </style>
 
-    <style name="Widget.SagerNet.CardView" parent="Widget.MaterialComponents.CardView">
+    <style name="Widget.SagerNet.CardView" parent="Widget.Material3.CardView.Filled">
         <item name="cardElevation">0dp</item>
         <item name="cardCornerRadius">@dimen/card_corner_radius</item>
         <item name="strokeColor">@color/card_stroke</item>
@@ -208,7 +211,7 @@
         <item name="cornerFamily">rounded</item>
         <item name="cornerSize">@dimen/input_corner_radius</item>
     </style>
-    <style name="Widget.SagerNet.TextInputLayout" parent="Widget.MaterialComponents.TextInputLayout.OutlinedBox">
+    <style name="Widget.SagerNet.TextInputLayout" parent="Widget.Material3.TextInputLayout.OutlinedBox">
         <item name="shapeAppearanceOverlay">@style/ShapeAppearanceOverlay.SagerNet.Input</item>
     </style>
 
@@ -217,11 +220,11 @@
         <item name="android:windowExitAnimation">@anim/popup_exit</item>
     </style>
 
-    <style name="Widget.SagerNet.PopupMenu" parent="Widget.MaterialComponents.PopupMenu">
+    <style name="Widget.SagerNet.PopupMenu" parent="Widget.Material3.PopupMenu">
         <item name="android:popupBackground">@drawable/bg_popup_menu</item>
         <item name="android:popupAnimationStyle">@style/PopupMenuAnimation</item>
     </style>
-    <style name="Widget.SagerNet.PopupMenu.Overflow" parent="Widget.MaterialComponents.PopupMenu.Overflow">
+    <style name="Widget.SagerNet.PopupMenu.Overflow" parent="Widget.Material3.PopupMenu.Overflow">
         <item name="android:popupBackground">@drawable/bg_popup_menu</item>
         <item name="android:popupAnimationStyle">@style/PopupMenuAnimation</item>
     </style>
@@ -233,22 +236,22 @@
         <item name="cornerSizeBottomLeft">0dp</item>
         <item name="cornerSizeBottomRight">0dp</item>
     </style>
-    <style name="Widget.SagerNet.BottomSheet" parent="Widget.MaterialComponents.BottomSheet.Modal">
+    <style name="Widget.SagerNet.BottomSheet" parent="Widget.Material3.BottomSheet.Modal">
         <item name="shapeAppearanceOverlay">@style/ShapeAppearanceOverlay.SagerNet.BottomSheet</item>
     </style>
-    <style name="ThemeOverlay.SagerNet.BottomSheetDialog" parent="ThemeOverlay.MaterialComponents.BottomSheetDialog">
+    <style name="ThemeOverlay.SagerNet.BottomSheetDialog" parent="ThemeOverlay.Material3.BottomSheetDialog">
         <item name="bottomSheetStyle">@style/Widget.SagerNet.BottomSheet</item>
     </style>
 
     <style name="ShapeAppearanceOverlay.SagerNet.Button" parent="">
         <item name="cornerFamily">rounded</item>
         <item name="cornerSize">@dimen/button_corner_radius</item>
     </style>
-    <style name="Widget.SagerNet.Button" parent="Widget.MaterialComponents.Button">
+    <style name="Widget.SagerNet.Button" parent="Widget.Material3.Button">
         <item name="shapeAppearanceOverlay">@style/ShapeAppearanceOverlay.SagerNet.Button</item>
     </style>
 
-    <style name="ShapeAppearance.SagerNet.NavItem" parent="ShapeAppearance.MaterialComponents.SmallComponent">
+    <style name="ShapeAppearance.SagerNet.NavItem" parent="ShapeAppearance.Material3.SmallComponent">
         <item name="cornerFamily">rounded</item>
         <item name="cornerSize">@dimen/nav_item_corner_radius</item>
     </style>
@@ -701,7 +704,7 @@
         <item name="routeProxyColor">@color/color_dracula_cyan</item>
     </style>
 
-    <style name="Theme.Start" parent="Theme.MaterialComponents.DayNight">
+    <style name="Theme.Start" parent="Theme.Material3.DayNight">
         <item name="android:navigationBarColor">@android:color/transparent</item>
         <item name="colorPrimary">@android:color/transparent</item>
         <item name="colorPrimaryDark">@android:color/transparent</item>