<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="center"
    android:columnCount="3"
    android:orientation="horizontal" >

    <Button
        android:id="@+id/button1"
        android:text="1"
        android:layout_column="0"
        android:layout_gravity="bottom|left"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button2"
        android:text="2"
        android:layout_column="1"
        android:layout_gravity="bottom|center"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button3"
        android:text="3"
        android:layout_column="2"
        android:layout_gravity="bottom|right"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>


    <Button
        android:id="@+id/button4"
        android:text="4"
        android:layout_column="0"
        android:layout_gravity="bottom|left"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button5"
        android:text="5"
        android:layout_column="1"
        android:layout_gravity="bottom|center"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button6"
        android:text="6"
        android:layout_column="2"
        android:layout_gravity="center|right"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button7"
        android:text="7"
        android:layout_column="0"
        android:layout_gravity="bottom|left"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button8"
        android:text="8"
        android:layout_column="1"
        android:layout_gravity="bottom|center"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>

    <Button
        android:id="@+id/button9"
        android:text="9"
        android:layout_column="2"
        android:layout_gravity="bottom|right"
        style="@style/Widget.AppCompat.Button.Borderless.Colored"
        android:layout_margin="@dimen/default_margin"
        android:padding="@dimen/default_padding"
        android:background="@color/AoDcolor"
        android:textColor="@color/white"/>
</GridLayout>