Transparent activity without one black line going across the screen?

I have created a real simple transparent activity by using a custom theme and color:

<style name="CustomTheme">
<item name="android:windowBackground">开发者_如何学编程@color/trans</item>
<item name="android:windowIsTranslucent">true</item>
</style>

<color name="trans">#00000000</color>

The only problem with this is when the activity starts one black line scrolls up the screen to the top. I assume this is the animation of the activity starting. Is there any way to change this so no line scrolls upwards?