This just change your Theme to Theme.AppCompat and it looks darker.
Refer that android:theme="@style/Theme.AppCompat" to this in your Manifest:
android:theme="@style/AppTheme">
So, do your stuffs in values -> Styles.xml.
Here is the Styles after that changes, you can customize that activity here too:
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>
</resources>
And about that Transparent, like i said you should use something like these stuffs:
in your Layout:
android:background="@android:color/transparent"
or:
How to create Transparent Activity in Android?