如何在android中定制PreferenceCategory的样式？

我希望更改PreferenceCategory的边框和PreferenceCategory标题的字体，我该怎么做？谢谢

顺便说一句，我找到了一些源代码。但我不知道format=“reference”的定义在哪里

？

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:robobunny="http://robobunny.com"
    android:key="AppPreference"
    android:summary="@string/PreferenceSummary"
    android:title="@string/Preference" >

     <PreferenceCategory android:title="@string/PreferenceCallCategory">         
        <ListPreference
          android:key="CallOption"
          android:defaultValue="OnlyAddress"       
          android:entries="@array/CallAndSMSOption"
          android:entryValues="@array/CallAndSMSOption_values"       
          android:title="@string/CallOptionTitle"
          android:summary="@string/CallOptionSummary"        
          android:layout="@layout/caller_custom_preference_layout"  
        />         
   </PreferenceCategory>             
</PreferenceScreen>




<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2006 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
-->

<!-- Layout used for PreferenceCategory in a PreferenceActivity. -->
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    style="?android:attr/listSeparatorTextViewStyle"
    android:id="@+android:id/title"
/>


<attr name="listSeparatorTextViewStyle" format="reference" />