custom edittext does not change in android

guys i cant seem to understand why my custom edittext does not change in virtual machine and on real device. but in the preview layout it changes. please help thanks in advance.

tetxbox.xml(res/drawable-hdpi/textbox.xml)

<?xml version="1.0" encoding="utf-8"?>

<item android:drawable="@drawable/textbox"></item>

---

activity_main.xml(res/layout/activity_main.xml)

    <EditText
        android:id="@+id/editTextUsername"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:ems="10"
        android:background="@drawable/textbox"
        android:paddingLeft="10dp"
        android:paddingRight="10dp"
        android:layout_marginBottom="5dp"
        android:hint="@string/etxt_username"
        android:inputType="text" >
    </EditText>