在1.17最新的Flutter版本中，Flutter对Android启动界面做了一点调整。众所周知，Flutter启动界面分为两部分：

第一部分是，Activity的LaunchTheme，这一部分是Android启动时的启动界面。

第二部分是，Flutter启动时的NormalTheme，这部分是Flutter启动时的启动界面。

两者在AndroidManifest.xml，都有配置，如下：

在1.17的Flutter创建的项目中，LaunchTheme和NormalTheme都放在了styles.xml了，这样就方便一起配置了（这部分跟以前的版本有所区别）。

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Theme applied to the Android Window while the process is starting -->
    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
        <!-- Show a splash screen on the activity. Automatically removed when
             Flutter draws its first frame -->
        <item name="android:windowBackground">@drawable/launch_background</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:color/white</item>
    </style>
</resources>

现在我们要修改启动白屏界面，就只要在styles.xml中进行配置了。比如，我这里改成如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- Theme applied to the Android Window while the process is starting -->
    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
        <!-- Show a splash screen on the activity. Automatically removed when
             Flutter draws its first frame -->
        <item name="android:windowBackground">@drawable/launch_background</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:color/white</item>
    </style> -->

    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
        <item name="android:windowBackground">@drawable/launch_background</item>
    </style>
</resources>