检索项目的父项时出错:找不到与给定名称相匹配的资源 'android:Theme.Material.Light'

Error retrieving parent for item: No resource found that matches the given name 'android:Theme.Material.Light'

我在 styles.xml 中收到此错误:

Error retrieving parent for item: No resource found that matches the given name 'android:Theme.Material.Light'.

清单中:

<uses-sdk
    android:minSdkVersion="16"
    android:targetSdkVersion="21" />

Android SDK 管理器:

我更新了所有 api 21 和额外内容。

正在订购和出口:

values-v21/styles.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="AppTheme" parent="android:Theme.Material.Light">

        <item name="android:colorPrimary">@color/primary</item>
        <item name="android:colorPrimaryDark">@color/primary_dark</item>
        <item name="android:colorAccent">@color/accent</item>
        <item name="android:textColorPrimary">@color/text_primary</item>
        <item name="android:textColor">@color/text_secondary</item>
        <item name="android:navigationBarColor">@color/primary_dark</item>

    </style>
</resources>  

控制台:

E:\workspace\WelcomeToL\app\src\main\res\values-v21\styles.xml:3: error: Error retrieving parent for item: No resource found that matches the given name 'android:Theme.Material.Light'.

E:\workspace\WelcomeToL\app\src\main\res\values-v21\styles.xml:7: error: Error: No resource found that matches the given name: attr 'android:colorAccent'.
 
E:\workspace\WelcomeToL\app\src\main\res\values-v21\styles.xml:5: error: Error: No resource found that matches the given name: attr 'android:colorPrimary'.
 
E:\workspace\WelcomeToL\app\src\main\res\values-v21\styles.xml:6: error: Error: No resource found that matches the given name: attr 'android:colorPrimaryDark'.

E:\workspace\WelcomeToL\app\src\main\res\values-v21\styles.xml:10: error: Error: No resource found that matches the given name: attr 'android:navigationBarColor'.

我不知道为什么这个错误仍然occurs.Anybody可以帮助我this.Thank你。

Error retrieving parent for item: No resource found that matches the given name 'android:Theme.Material.Light'.

Material.Light 项目主题需要 API 级别 21。为从 Properties->Android->Project Build TargetAPI 21 的项目设置 Project Build Target