如何使用Appcompat v7 21，工具栏和DrawerLayout动画汉堡到箭头

I am using the android.support.v7.widget.Toolbar with a android.support.v4.widget.DrawerLayout. It works fine, the Burger icon is shown when the Navigation Drawer is closed, and the Arrow icon is shown when the Drawer is open. I want to disable the drawer and animate the Burger icon into Arrow on some event in the app. I have tried to set the lock mode to closed, but the v7.app.ActionBarDrawerToggle is still showing the Burger and it opens the Drawer.I am using the android.support.v7.widget.Toolba