问找不到PreferenceScreen类

EN

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
        <PreferenceCategory
                android:title="First Category">
                <CheckBoxPreference
....

com.android.layoutlib.bridge.MockView cannot be cast to android.view.ViewGroup
Exception details are logged in Window > Show View > Error Log
The following classes could not be found:
- PreferenceCategory (Fix Build Path, Edit XML)
- PreferenceScreen (Fix Build Path, Edit XML)