ScrollView is a scrolling container used when content exceeds the screen dimensions. A typical implementation appears as follows:

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white" >
    <LinearLayout
        android:id="@+id/content_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >
        <TextView
            android:id="@+id/first_text"
            android:layout_width="match_parent"
            android:background="@color/gray"
            android:layout_height="match_parent"
            android:text="Sample Text" />
    </LinearLayout>
</ScrollView>

In this scenario, the ScrollView (white background) occupies the full height, but the inner TextView (gray background) does not expand accordingly. Despite setting layout_height="match_parent" on the TextView, it fails to fill the available space. This occurs because the immediate child of ScrollView (LinearLayout) has its height set to wrap_content, which constrains the TextView's height.

To resolve this, add android:fillViewport="true" to the ScrollView declaration:

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true" >

This attribute ensures that the ScrollView expands its content to fill the viweport when the content is smaller than the container.