fix: sync activity background to theme

Author: lisonge

app/src/main/kotlin/li/songe/gkd/ui/style/Theme.kt

@@ -20,6 +20,7 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.toArgb
 import androidx.core.view.WindowInsetsControllerCompat
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -72,6 +73,10 @@ fun AppTheme(
                 isAppearanceLightStatusBars = !darkTheme
             }
         }
+        val bg = colorScheme.background.toArgb()
+        LaunchedEffect(darkTheme, bg) {
+            activity.window.decorView.setBackgroundColor(bg)
+        }
     }
 
     val isTalkbackEnabledFlow = remember {

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

@@ -1,6 +1,8 @@
 <resources>
 
-    <style name="AppTheme" parent="android:Theme.Material.Light.NoActionBar" />
+    <style name="AppTheme" parent="android:Theme.Material.Light.NoActionBar">
+        <item name="android:windowBackground">@android:color/transparent</item>
+    </style>
 
     <style name="SplashScreenTheme" parent="Theme.SplashScreen">
         <item name="windowSplashScreenAnimatedIcon">