Flutter 黑屏问题，在启动页和Flutter页面之间黑屏。

解决方法：

在 AndroidManifest.xml 的 <activity> </activity> 中添加

<meta-data
    android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
    android:value="true" />
<meta-data
    android:name="io.flutter.embedding.android.SplashScreenDrawable"
    android:resource="@drawable/launch_background" />

完整 AndroidManifest.xml如下：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.demo.ts">
    <application
        android:name="io.flutter.app.FlutterApplication"
        android:icon="@mipmap/ic_launcher"
        android:label="demo"
        android:usesCleartextTraffic="true" >
        <activity
            android:name=".MainActivity"
         android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
            android:hardwareAccelerated="true"
            android:launchMode="singleTop"
            android:theme="@style/LaunchTheme"
            android:windowSoftInputMode="adjustResize">
            <meta-data
                android:name="io.flutter.app.android.SplashScreenUntilFirstFrame"
                android:value="true" />
            <meta-data
                android:name="io.flutter.embedding.android.SplashScreenDrawable"
                android:resource="@drawable/launch_background" />

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


        <!-- Don't delete the meta-data below.
             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
        <meta-data
            android:name="flutterEmbedding"
            android:value="2" />
    </application>
</manifest>