android画空心圆

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <padding
        android:left="2dp"
        android:top="1dp"
        android:right="2dp"
        android:bottom="1dp" />
    <solid android:color="#00ffffff"/>
    <stroke
        android:width="2dp"
        android:color="#339933" />
    <size android:width="15dp"
        android:height="15dp" />

</shape>