feature: implemented native splash and remove custom flutter splash feature

Author: fulleni

android/app/src/main/res/drawable-night-v21/background.png

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item>
+        <bitmap android:gravity="fill" android:src="@drawable/background"/>
+    </item>
+</layer-list>

android/app/src/main/res/drawable-night-v21/launch_background.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item>
+        <bitmap android:gravity="fill" android:src="@drawable/background"/>
+    </item>
+</layer-list>

android/app/src/main/res/drawable-night/background.png

@@ -1,12 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Modify this file to customize your launch splash screen -->
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:drawable="?android:colorBackground" />
-
-    <!-- You can insert your own image assets here -->
-    <!-- <item>
-        <bitmap
-            android:gravity="center"
-            android:src="@mipmap/launch_image" />
-    </item> -->
+    <item>
+        <bitmap android:gravity="fill" android:src="@drawable/background"/>
+    </item>
 </layer-list>

android/app/src/main/res/drawable-night/launch_background.xml

@@ -1,12 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Modify this file to customize your launch splash screen -->
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:drawable="@android:color/white" />
-
-    <!-- You can insert your own image assets here -->
-    <!-- <item>
-        <bitmap
-            android:gravity="center"
-            android:src="@mipmap/launch_image" />
-    </item> -->
+    <item>
+        <bitmap android:gravity="fill" android:src="@drawable/background"/>
+    </item>
 </layer-list>

android/app/src/main/res/drawable-v21/background.png

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is on -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:forceDarkAllowed">false</item>
+        <item name="android:windowFullscreen">false</item>
+        <item name="android:windowDrawsSystemBarBackgrounds">false</item>
+        <item name="android:windowLayoutInDisplayCutoutMode">shortEdges</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+         
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

android/app/src/main/res/drawable-v21/launch_background.xml

@@ -5,6 +5,10 @@
         <!-- Show a splash screen on the activity. Automatically removed when
              the Flutter engine draws its first frame -->
         <item name="android:windowBackground">@drawable/launch_background</item>
+        <item name="android:forceDarkAllowed">false</item>
+        <item name="android:windowFullscreen">false</item>
+        <item name="android:windowDrawsSystemBarBackgrounds">false</item>
+        <item name="android:windowLayoutInDisplayCutoutMode">shortEdges</item>
     </style>
     <!-- Theme applied to the Android Window as soon as the process has started.
          This theme determines the color of the Android Window while your