when I am using my own background theme for spinner it is stretching icon.

my spinner code is:
<Spinner android:id="@+id/spinnerCategory" style="@style/spinner"
android:entries="@array/category_array" android:prompt="@string/category_prompt"
android:background="@drawable/spinner" />
my spinner.xml is:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_window_focused="false" android:state_enabled="true"
android:drawable="@drawable/btn_dropdown_normal" />
<item android:state_pressed="true" android:drawable="@drawable/btn_dropdown_pressed" />
<item android:state_focused="true" android:state_enabled="true"
android:drawable="@drawable/btn_dropdown_selected" />
<item android:state_enabled="true" android:drawable="@drawable/btn_dropdown_normal" />
</selector>
and images I copied from the sdk 4.
How can I stop spinner icon stretching?
I had the same problem. I just hard-coded the height of spinner to somewhere near about 48-50 dip.