Trouble aligning "Text View" widget to the center of the android screen.

When I click and drag the "text view" widget into the graphical layout, much like the video, some green cross hairs appear. However when I release the mouse button in the center, the "text view" widget returns to the upper left corner of the layout.

I noticed that in the video the xml used is:

android:layout_center_InParent = "true"

Where as mine is displayed:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="fill" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.crystalball.MainActivity$PlaceholderFragment" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="TextView" />

</RelativeLayout>

I've tried editing the xml but it doesn't seem to change the position of my "text view" widget or my "button" widget. Any idea what I'm doing wrong? Many thanks!

-Jeff