Android Alert Dialog with extra background

Question

I recently migrated my app to Material Design and I stumbled upon this problem with my Alert Dialogs:

I'm applying the dialog style like this:

<item name="android:alertDialogTheme">@style/Theme.AlertDialog</item>

and Theme.AlertDialog looks like this:

<style name="Theme.AlertDialog" parent="Base.V14.Theme.AppCompat.Dialog">
    <item name="colorPrimary">@color/theme_primary</item>
    <item name="colorPrimaryDark">@color/theme_primary_dark</item>
    <item name="colorAccent">@color/theme_accent_dark</item>
</style>

This is happening on my Kitkat device and it works fine on Lollipop. Can you help me with getting rid of that outer background?

Answer 1

The point is here:

<style name="Theme.AlertDialog" parent="Base.V14.Theme.AppCompat.Dialog">
    ...
    <item name="colorPrimary">@color/theme_primary</item>
    <item name="colorPrimaryDark">@color/theme_primary_dark</item>
    <item name="colorAccent">@color/theme_accent_dark</item>
    ...
    <item name="android:windowBackground">@android:color/transparent</item>
    ...
</style>

Answer 2

As ironman told me here, be sure that you import the right class.

Right : import android.support.v7.app.AlertDialog;

Wrong : import android.app.AlertDialog;