Fix Shell page transition color blinking on Android

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellContentFragment.cs

@@ -9,6 +9,8 @@
 using AndroidX.Core.View;
 using AndroidX.Fragment.App;
 using Google.Android.Material.AppBar;
+using Microsoft.Maui.Controls.Handlers.Compatibility;
+using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Platform;
 using AndroidAnimation = Android.Views.Animations.Animation;
 using AnimationSet = Android.Views.Animations.AnimationSet;
@@ -136,6 +138,11 @@ public override AView OnCreateView(LayoutInflater inflater, ViewGroup container,
 
 			_root = inflater.Inflate(Controls.Resource.Layout.shellcontent, null).JavaCast<CoordinatorLayout>();
 
+			// Set theme-aware background color immediately to prevent white flash during transitions.
+			// The CoordinatorLayout is inflated without a background color, which can cause
+			// white flash during fragment transitions when using dark theme.
+			_root.SetBackgroundColor(ShellRenderer.DefaultBottomNavigationViewBackgroundColor.ToPlatform());
+
 			MauiWindowInsetListener.SetupViewWithLocalListener(_root);
 
 			var shellContentMauiContext = _shellContext.Shell.Handler.MauiContext.MakeScoped(layoutInflater: inflater, fragmentManager: ChildFragmentManager);

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellItemRenderer.cs

@@ -13,6 +13,7 @@
 using Google.Android.Material.Navigation;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
+using Microsoft.Maui.Controls.Handlers.Compatibility;
 using Microsoft.Maui.Graphics;
 using AColor = Android.Graphics.Color;
 using AView = Android.Views.View;
@@ -76,6 +77,14 @@ public override AView OnCreateView(LayoutInflater inflater, ViewGroup container,
 			_navigationArea = PlatformInterop.CreateNavigationBarArea(context, _outerLayout);
 			_bottomView = PlatformInterop.CreateNavigationBar(context, Resource.Attribute.bottomNavigationViewStyle, _outerLayout, this);
 
+			// Set theme-aware background colors immediately to prevent white flash during transitions.
+			// The BottomNavigationView is created with Color.WHITE in PlatformInterop.java, but the
+			// correct theme-aware color should be applied immediately before any UI is rendered.
+			// We also set the navigation area background to prevent white flash during fragment transitions.
+			var themeAwareBackgroundColor = ShellRenderer.DefaultBottomNavigationViewBackgroundColor.ToPlatform();
+			_bottomView.SetBackgroundColor(themeAwareBackgroundColor);
+			_navigationArea.SetBackgroundColor(themeAwareBackgroundColor);
+
 			if (ShellItem is null)
 				throw new InvalidOperationException("Active Shell Item not set. Have you added any Shell Items to your Shell?");
 

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellSectionRenderer.cs

@@ -16,6 +16,8 @@
 using Google.Android.Material.AppBar;
 using Google.Android.Material.Tabs;
 using Microsoft.Extensions.Logging;
+using Microsoft.Maui.Controls.Handlers.Compatibility;
+using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Platform;
 using AToolbar = AndroidX.AppCompat.Widget.Toolbar;
 using AView = Android.Views.View;
@@ -102,6 +104,12 @@ public override AView OnCreateView(LayoutInflater inflater, ViewGroup container,
 
 			var context = Context;
 			var root = PlatformInterop.CreateShellCoordinatorLayout(context);
+
+			// Set theme-aware background color immediately to prevent white flash during transitions.
+			// The CoordinatorLayout is created without a background, which can cause white flash
+			// during fragment transitions when using dark theme.
+			root.SetBackgroundColor(ShellRenderer.DefaultBottomNavigationViewBackgroundColor.ToPlatform());
+
 			var appbar = PlatformInterop.CreateShellAppBar(context, Resource.Attribute.appBarLayoutStyle, root);
 
 			MauiWindowInsetListener.SetupViewWithLocalListener(root);