默认图标识竖直的三个省略号
修改成自定义图标
需要修改主题Theme
<style name="AppTheme" parent="AppBaseTheme">
<item name="android:actionOverflowButtonStyle">@style/Action_OverflowButtonStyle</item>
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
</style>
<style name="Action_OverflowButtonStyle" >
<item name="android:src">@drawable/actionbar_add_icon</item>
</style>
大功告成