how to align text vertically center in android

Your TextView Attributes need to be something like,

<TextView ... 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_vertical|right" ../>

Now, Description why these need to be done,

 android:layout_width="match_parent"
 android:layout_height="match_parent"

Makes your TextView to match_parent or fill_parent if You don’t want to be it like, match_parent you have to give some specified values to layout_height so it get space for vertical center gravity. android:layout_width="match_parent" necessary because it align your TextView in Right side so you can recognize respect to Parent Layout of TextView.

Now, its about android:gravity which makes the content of Your TextView alignment. android:layout_gravity makes alignment of TextView respected to its Parent Layout.

Update:

As below comment says use fill_parent instead of match_parent. (Problem in some device.)