button:gravity="right" is not working

button:gravity="right" is not working

i am desinging a xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.05"
android:background="#000000"
android:orientation="horizontal" >
<Button
android:id="@+id/btncancel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="left|center"
android:background="#CCCCCC"
android:text="Cancel" />
<Button
android:id="@+id/btnadd"
android:layout_width="82dp"
android:layout_height="wrap_content"
android:gravity="right"
android:background="#3399FF"
android:text="Add" />
</LinearLayout>
</LinearLayout>
for button "Add" android:gravity=right is not working.i have give a
layout:margin,then only its moving right.can anyone help me out.