错误：
W/FlutterActivityAndFragmentDelegate(10811): A splash screen was provided to Flutter, but this is deprecated. See flutter.dev/go/android-splash-migration for migration steps.
解决：
AndroidManifest.xml文件，注释掉以下内容即可。
<meta-data
android:name="io.flutter.embedding.android.SplashScreenDrawable"
android:resource="@drawable/launch_background"
/>