Why is the EditText not showing in android?

I am completely new to android. The EditText is not showing up in the graphical layout.

xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <EditText 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="text"
        android:ems="10"
        />

</LinearLayout>

There is also a little yellow underline after ''. When I put my mouse cursor on it, it says nothing. I couldn't find the answer I was looking for. The graphical layout looks less brighter than the original, and is as follows:

And no I haven't run the program yet. Plz.