Android-啓動頁「android:windowBackground」變型？

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@android:color/white" />
    <item>
        <bitmap
            android:gravity="bottom"
            android:scaleType="centerCrop"
            android:src="@drawable/bg_splash"
            android:tileMode="disabled" />
    </item>
</layer-list>

    <style name="main_splash_activity_style" parent="Theme.AppCompat">
        <item name="android:windowBackground">@drawable/main_bitmap_splash_bg</item>
        <item name="android:windowFullscreen">true</item>
        <!--<item name="android:windowIsTranslucent">false</item>-->
        <!--<item name="windowActionBar">false</item>-->
        <!--<item name="android:windowDisablePreview">true</item>-->
        <!--<item name="android:windowContentOverlay">@null</item>-->
        <item name="windowNoTitle">true</item>
    </style>

<activity
            android:name=".activity.SplashActivity"
            android:screenOrientation="portrait"
            android:theme="@style/main_splash_activity_style">
</activity>