drawable 参考链接

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--
    android:width：边框的宽度
    android:dashGap：虚线间距宽度
    android:dashWidth：虚线宽度
    -->
    <stroke
        android:width="1dp"
        android:color="@android:color/darker_gray"
        android:dashWidth="5dp"
        android:dashGap="10dp" />
</shape>

效果图

带下划线的背景

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <item>
        <shape>
            <solid android:color="@color/purple_200" />
        </shape>
    </item>
    <item android:bottom="5dp">
        <shape>
            <solid android:color="@color/white" />
        </shape>
    </item>
</layer-list>

效果图

button / textColor selector

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="@android:color/holo_blue_light" android:state_pressed="true" />
    <item android:color="@android:color/holo_blue_light" android:state_checked="true" />
    <item android:color="@android:color/holo_blue_light" android:state_selected="true" />
    <item android:color="@android:color/holo_red_light" />
</selector>