增加启动图

android/app/src/main/AndroidManifest.xml

@@ -59,6 +59,14 @@
             <meta-data
                 android:name="io.flutter.embedding.android.NormalTheme"
                 android:resource="@style/NormalTheme" />
+            <!-- Displays an Android View that continues showing the launch screen
+                 Drawable until Flutter paints its first frame, then this splash
+                 screen fades out. A splash screen is useful to avoid any visual
+                 gap between the end of Android's launch screen and the painting of
+                 Flutter's first frame. -->
+            <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" />

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

@@ -1,12 +0,0 @@
-<?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> -->
-</layer-list>

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

@@ -1,12 +1,8 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!-- Modify this file to customize your launch splash screen -->
+<?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>
+    <item>
         <bitmap
-            android:gravity="center"
-            android:src="@mipmap/launch_image" />
-    </item> -->
+            android:gravity="fill"
+            android:src="@drawable/launch_image" />
+    </item>
 </layer-list>