selector设置按钮或者一些点击控件在点击时的效果

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

    <item android:drawable="@drawable/ic_toc_white_24dp" android:state_pressed="true"/>
    <item android:drawable="@drawable/ic_toc_black_24dp" android:state_focused="false" android:state_pressed="false"/>
    <item android:drawable="@drawable/ic_toc_white_24dp"  android:state_focused="true"/>
    <item android:drawable="@drawable/ic_toc_black_24dp" android:state_focused="false"/>

</selector>