问单选按钮在选择单选按钮时，使单选按钮外圈的颜色与颜色不同。

EN

<RadioButton
    android:id="@+id/radio_button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:checked="true"
    android:buttonTint="OUTER_CIRCLE_COLOR_CODE"/>

android:button="@drawable/rb_bg"

<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true" android:drawable="@drawable/button_selected"/>
<item android:state_checked="false" android:drawable="@drawable/button_unselected"/>
</selector>

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

<item>
    <shape android:shape="oval">
        <solid android:color="@color/divider_color" />
    </shape>
</item>

<item android:bottom="1dp">
    <shape android:shape="oval">
        <solid android:color="@android:color/white" />
    </shape>
</item>

<item
    android:bottom="4dp"
    android:left="4dp"
    android:right="4dp"
    android:top="4dp">
    <shape android:shape="oval">
        <size
            android:width="16dp"
            android:height="16dp" />
        <solid android:color="@color/blue" />
    </shape>
</item>

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item>
    <shape android:shape="oval">
        <solid android:color="@color/divider_color"/>
    </shape>
</item>
<item
    android:bottom="1dp">
    <shape android:shape="oval">
        <size android:height="24dp" android:width="24dp"/>
        <solid android:color="@android:color/white"/>
    </shape>
</item>