<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <!-- solid表示远的填充色 -->
    <solid android:color="@color/colorPrimary" />
    <!-- stroke则代表远的边框线 -->
    <stroke
        android:width="1dp"
        android:color="@color/colorPrimary" />
    <!-- size控制高宽 -->
    <size
        android:height="20dp"
        android:width="20dp" />
</shape>