Android Studio "kann nicht resolove symbol "Theme""

Bin ich mit android studio 0.8.4
wenn ich verlängern @style/Theme.AppCompat.Light -, android-studio, sagt can't resolove symbol 'Theme' mit Roter Schrift gefärbt Theme. aber wenn ich dieses Projekt, es läuft auch gut. Ich kann nicht wissen, wie dieses problem zu lösen. belows sind meine codes.

styles.xml

<resources>
    <!-- the theme applied to the application or activity -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    </style>
</resources>

bauen.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 20
    buildToolsVersion "20.0.0"

    defaultConfig {
        applicationId "kr.co.hiworks.office"
        minSdkVersion 9
        targetSdkVersion 19
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    lintOptions {
        disable 'InvalidPackage'
    }

    packagingOptions {
        exclude 'META-INF/services/javax.annotation.processing.Processor'
    }

}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:support-v4:19.+'
    compile 'com.android.support:appcompat-v7:19.+'
    compile 'com.jakewharton:butterknife:5.1.1'
    compile 'com.nineoldandroids:library:2.4.0'
    compile 'com.mcxiaoke.volley:library:1.0.6'
    compile 'com.github.satyan:sugar:1.3'
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="kr.co.hiworks.office" >

    <application
        android:name=".BaseApplication"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <meta-data android:name="DATABASE" android:value="hiworks_office.db" />
        <meta-data android:name="VERSION" android:value="1" />
        <meta-data android:name="QUERY_LOG" android:value="true" />
        <meta-data android:name="DOMAIN_PACKAGE_NAME" android:value="kr.hiworks.office.models" />
        <activity
            android:name=".activities.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>