Fix position of Relativelayout in Activity

Question

Good afternoon.

I want to fix the position of two RelativeLayout on the screen, but when the user changes the text of the TextSwitcher the RelativeLayout the one it belongs to increases in size, and so the Jump button is moving up and down and would like to leave it in the same place. How can I fix this problem?

Follows the XML:

<LinearLayout 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:orientation="vertical"
    tools:context="br.com.emergencyonline.Introduction" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/introduction_emergency_online"
    android:paddingTop="30dp"
    android:layout_gravity="center" />

<RelativeLayout 
    android:id="@+id/rlDescriptions"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:padding="50dp"
    android:background="@color/button_material_light">

<TextSwitcher 
    android:id="@+id/tsIntroduction"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center" />

</RelativeLayout>

<RelativeLayout 
    android:id="@+id/rlPular"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@color/background_material_dark">

<Button 
    android:id="@+id/btnPular"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/jump" 
    android:gravity="center"
    android:layout_centerInParent="true"/>

</RelativeLayout> 

</LinearLayout>