Попробуйте вот так
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imageView2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:contentDescription="@string/app_name"
android:minHeight="250dp"
android:layout_above="@+id/tvText"
android:src="@drawable/kid" />
<TextView
android:id="@+id/tvText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:background="@color/colorAccent"
android:text="@string/large_text" />
</RelativeLayout>
OUTPUT
Когда большой текст
![enter image description here](https://i.stack.imgur.com/yA9to.png)
Когда маленький текст
![enter image description here](https://i.stack.imgur.com/Xn1kx.png)
UPDATE
<string name="large_text">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce pulvinar nec justo id bibendum.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce pulvinar nec justo id bibendum.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce pulvinar nec justo id bibendum.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce pulvinar nec justo id bibendum.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce pulvinar nec justo id bibendum.Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis bibendum mattis risus eget pulvinar. Praesent commodo erat enim, id congue sem tristique vitae. Proin vitae accumsan justo, ut imperdiet tellus. Mauris neque nibh, hendrerit id tortor vel, congue sagittis odio. Morbi elementum lobortis maximus. Etiam sit amet porttitor massa. Fusce sed magna quis arcu tincidunt finibus vitae id erat. Pellentesque massa mi, imperdiet eget accums</string> <!-- TODO: Remove or change this placeholder text -->
<string name="small_text">Hello World Lorem ipsum dolor sit amet, consectetur adipiscing elit
Hello World Lorem ipsum dolor sit amet, consectetur adipiscing elit
Hello World Lorem ipsum dolor sit amet, consectetur adipiscing elit</string>