PreferenceScreen theme

Question

I set preference to preference screen.

The main screen is fine, but sub-screens are dark and I can't see the title of elements, only blue descriptions.

If I scroll down, the theme is changed to light.

I have tried adding android:background="AppTheme" to preferencescreen element, but nothing happened.

edit (Meph):

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">


        <!-- Network screen  -->

        <PreferenceScreen
                android:title="@string/pref_network_screen"
                android:key="prefNetworkScreen">
                android:background="@style/AppTheme">
                <CheckBoxPreference
                        android:title="@string/pref_network_update"
                        android:defaultValue="false"
                        android:summary="@string/pref_network_update_description"
                        android:key="prefUpdate" />
                <ListPreference
                        android:title="@string/pref_network_type"
                        android:summary="@string/pref_network_type_description"
                        android:key="prefNetworkType"
                        android:defaultValue="1"
                        android:entries="@array/prefNetworkArray"
                        android:entryValues="@array/prefNetworkValues" />
         </PreferenceScreen>




        <!-- Network screen  -->   

        <PreferenceScreen
            android:title="@string/pref_network_screen"
            android:key="prefNetworkScreen">
            <CheckBoxPreference
                    android:title="@string/pref_network_update"
                    android:defaultValue="false"
                    android:summary="@string/pref_network_update_description"
                    android:key="prefUpdate" />
            <ListPreference
                    android:title="@string/pref_network_type"
                    android:summary="@string/pref_network_type_description"
                    android:key="prefNetworkType"
                    android:defaultValue="1"
                    android:entries="@array/prefNetworkArray"
                    android:entryValues="@array/prefNetworkValues" />
         </PreferenceScreen>
</PreferenceScreen>

and styles.xml:

<resources>

    <style name="AppTheme" parent="android:Theme.Light" />

</resources>