res/drawable/ic_notification_block.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
Copyright (C) 2019 The Android Open Source Project

   Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

         http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
-->
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/back">
        <shape android:shape="oval">
            <solid
                android:color="@android:color/transparent" />
            <size
                android:height="48dp"
                android:width="48dp"/>
            <stroke android:width="1dp"
                    android:color="@color/notification_block_color"/>
        </shape>
    </item>
    <item
        android:id="@+id/fore"
        android:gravity="center">
        <vector
            android:height="24dp"
            android:width="24dp"
            android:viewportHeight="24"
            android:viewportWidth="24">
            <path
                android:fillColor="@color/notification_block_color"
                android:pathData="M12.0,2.0C6.48,2.0 2.0,6.48 2.0,12.0s4.48,10.0 10.0,10.0 10.0,-4.48 10.0,-10.0S17.52,2.0 12.0,2.0zM4.0,12.0c0.0,-4.42 3.58,-8.0 8.0,-8.0 1.85,0.0 3.5,0.63 4.9,1.69L5.69,16.9C4.63,15.55 4.0,13.85 4.0,12.0zm8.0,8.0c-1.85,0.0 -3.55,-0.63 -4.9,-1.69L18.31,7.1C19.37,8.45 20.0,10.15 20.0,12.0c0.0,4.42 -3.58,8.0 -8.0,8.0z"/>
        </vector>
    </item>
</layer-list>