包不存在android studio

Question

尝试执行以下代码行时出现以下错误。

import com.example.albert.helper.SessionManager;

错误：（15,33）错误：包com.example.albert.helper不存在

apply plugin: 'com.android.library'

android {
    compileSdkVersion 21
    buildToolsVersion '21.0.0'

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_7
        targetCompatibility JavaVersion.VERSION_1_7
    }
}

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