这是我的Gradle文件：

apply plugin: 'com.android.library'
 
android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"
 
    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'),'proguard-rules.pro'
        }
    }
}
 
dependencies {
    compile fileTree(include: ['*.jar'],dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'me.zhanghai.android.materialprogressbar:library:1.1.4'
    compile 'com.android.support:design:23.1.1'
}

你可以看到,我已经添加了import com.android.support:design:23.1.1,但结果我得到错误：

error: package android.support.design.R does not exist

如何解决这个问题？