问导入android.support.v7.app无法解析

EN

    apply plugin: 'com.android.application'
    android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.example.android.effectivenavigation"
        minSdkVersion 14
        targetSdkVersion 14
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.1.1'
    compile 'com.android.support:support-v4:22.1.1'
}

    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.android.effectivenavigation"
        android:versionCode="1"
    android:versionName="1.0">

    <uses-sdk android:minSdkVersion="14" />

    <application android:label="@string/app_name"
        android:icon="@drawable/ic_launcher"
        android:theme="@android:style/Theme.Holo.Light.DarkActionBar">

        <activity android:name=".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>

        <activity android:name=".CollectionDemoActivity" android:label="@string/demo_collection" />

    </application>
</manifest>