R.layout.activity_main

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="org.androidtown.myselector.MainActivity">

    <Button
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginTop="171dp"
        android:id="@+id/button"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:background="@drawable/arrow_left_selector" />

    <!--백그라운드에 xml 을 지정한다.-->


</RelativeLayout>

arrow_left_selector.xml 

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

<!--    버튼을 눌렀을 경우-->
    <item
        android:state_pressed="true"
        android:drawable="@drawable/arrow_left_clicked"
        />

    <!--정상적인경우-->
    <item
        android:drawable="@drawable/arrow_left_normal"
        />

</selector>

​​​​​​​