1.在drawable文件下，新建seletor，作為button的背景，這裏我用的是兩個圓角的shape

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/shape_btn_cycle_normal"/>
    <item android:state_pressed="true" android:drawable="@drawable/shape_btn_cycle_press"
 
/>
</selector>

　　shape_btn_cycle_normal

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        android:bottomLeftRadius="20dp"
        android:bottomRightRadius="20dp"
        android:topLeftRadius
 
="20dp"
        android:topRightRadius="20dp"/>
    <solid android:color="@color/colorWhite"/>

</shape>

　　shape_btn_cycle_press

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        
 
android:bottomLeftRadius="20dp"
        android:bottomRightRadius="20dp"
        android:topLeftRadius="20dp"
        android:topRightRadius="20dp"/>
    <solid android:color="@color/colorGray"/>

</shape>

　　2.在drawable-v21下，新建同selector名的ripple，如上，我的selector是selector_btn_cycle_bg,這裏drawable-v21下新建selector_btn_cycle_bg.xml

<?xml version="1.0" encoding="utf-8"?>
<ripple xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="@color/colorGray"> //選中的水波紋的顏色
    <item android:drawable="@drawable/shape_btn_cycle_normal"/>//未選中的背景狀態

</ripple>

android 水波紋效果實現