优化

app/src/main/res/drawable/ic_launcher4.xml

@@ -3,9 +3,6 @@
     android:height="108dp"
     android:viewportWidth="108"
     android:viewportHeight="108">
-    <path
-        android:pathData="M0,0h108v108h-108z"
-        android:fillColor="#FFFFFF" />
     <path
         android:pathData="M55.659,79.068c-1.258,0 -2.521,-0.094 -3.753,-0.279c-0.773,-0.115 -1.307,-0.838 -1.19,-1.611s0.841,-1.311 1.612,-1.191c1.093,0.164 2.214,0.248 3.331,0.248c12.261,0 22.235,-9.975 22.235,-22.235c0,-12.26 -9.975,-22.234 -22.235,-22.234c-10.531,0 -19.695,7.479 -21.79,17.781c-0.155,0.768 -0.902,1.262 -1.671,1.107c-0.767,-0.156 -1.263,-0.904 -1.106,-1.672c2.361,-11.618 12.693,-20.051 24.567,-20.051c13.823,0 25.069,11.246 25.069,25.068C80.729,67.822 69.482,79.068 55.659,79.068z"
         android:fillColor="#568FCC" />

app/src/main/res/drawable/ic_launcher4_b.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:pathData="M0,0h108v108h-108z"
+        android:fillColor="#FFFFFF" />
+</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -2,4 +2,5 @@
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
     <background android:drawable="@drawable/ic_launcher1_b" />
     <foreground android:drawable="@drawable/ic_launcher1" />
+    <monochrome android:drawable="@drawable/ic_launcher4" />
 </adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/launcher4.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@color/md_grey_50" />
+    <background android:drawable="@drawable/ic_launcher4_b" />
     <foreground android:drawable="@drawable/ic_launcher4" />
 </adaptive-icon>