How to alignment the center position of the button in Android?

How to alignment the center position of the button in Android?

In the XML layout, can able to set the center postion by using the "android:layout_gravity", the sample XML code as below,

<button android:text="ClickMe" 
    android:id="@+id/btClick" 
    android:layout_width="100px" 
    android:gravity="center_vertical|center_horizontal" 
    android:layout_height="wrap_content" 
    android:layout_gravity="center_vertical|center_horizontal|center" >
</button>

Attribute usage,

• android:gravity   >  align the text
• android:layout_gravity > align the layout position of the element 
• android:layout_width > width of the button
• android:layout_height > hight of the button ( wrag_content sense autoresize by using text )