Align radio buttons by their checkradio

Question

I'm using two radio buttons inside a radiogroup one below the other. THe upper button has as text "to" and the other has "from". What I want is that both will be in the center but they will be aligned by their checkradio. I tried this :

<RadioGroup
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:id="@+id/rgroup_pk"
                android:gravity="center">

                <RadioButton
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:id="@+id/rbtn_to"
                    android:text="@string/title_to"
                    android:checked="true"
                    android:gravity="center|center_vertical" />


                <RadioButton
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:id="@+id/rbtn_from"
                    android:text="@string/title_from"
                    android:gravity="center|center_vertical" />

            </RadioGroup>

THis makes the buttons stay in the vertical and horizontal center, but because of their text has different size what it shows is this (if "x" is the checkradio):

                   X to
                  X from

And what I want is this:

                   x to
                   x from

Answer 1

Include the RadioButtons in a RelativeLayout.

    <RadioGroup
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/rgroup_pk"
        android:gravity="center">

        <RelativeLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center|center_vertical">

            <RadioButton
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:id="@+id/rbtn_to"
                 android:text="TO"
                 android:checked="true"/>

            <RadioButton
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:id="@+id/rbtn_from"
                 android:text="FROM"
                 android:layout_below="@+id/rbtn_to"/>
        </RelativeLayout>
    </RadioGroup>

Notice the android:layout_below="@+id/rbtn_to". This, as the name suggest, places the second RadioButton below the first and not overlap it like is normal in a RelativeLayout.