activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout ...
    <LinearLayout ...
    
        <Button
            android:id="@+id/share_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="Share content" />
            
            ...
    </LinearLayout>
</RelativeLayout>