在style或自定义theme(v21)中添加如下：
<item name="android:colorControlHighlight">#20000000</item>
并在item_roll.xml中加入：
android:clickable="true"
android:background="?attr/selectableItemBackground"
问题产生原因：
“It turns out this is working as intended. The standard Material theme colorControlHighlight value is #40ffffff. So on a white background, this will not show up. Changing the highlight color to something else works, and/or changing the background color of the object.”
————————stackoverflow
也就是说Material Theme的colorcontrolHighlight默认值是#40ffffff。在白色背景下动画效果并不会显现。解决方法是将背景颜色改变，或者更改Hightlight color。
AppCompat tinting attributs:
First, you should take a look to appCompat lib article there and to different attributs you can set:
colorPrimary: The primary branding color for the app. By default, this is the color applied to the action bar background.
colorPrimaryDark: Dark variant of the primary branding color. By default, this is the color applied to the status bar (via statusBarColor) and navigation bar (via navigationBarColor).
colorAccent: Bright complement to the primary branding color. By default, this is the color applied to framework controls (via colorControlActivated).
colorControlNormal: The color applied to framework controls in their normal state.
colorControlActivated: The color applied to framework controls in their activated (ex. checked, switch on) state.
colorControlHighlight: The color applied to framework control highlights (ex. ripples, list selectors).
colorButtonNormal: The color applied to framework buttons in their normal state.
colorSwitchThumbNormal: The color applied to framework switch thumbs in their normal state. (switch off)