错误：任务＆＃39;：app：transformClassesWithDexForDebug＆＃39;执行失败。 ＆GT; COM

Question

我收到此错误，我不知道如何修复它。我有java 7.提前谢谢你。我是新手编写的，我根本没有任何过去的经验，我已经完成了非常基本的纸上编程但仍然如此。另外我还需要做些什么才能在android模拟器中测试这个应用程序？感谢

 <activity
    android:name=".activity.MainActivity"
    android:configChanges="orientation|keyboardHidden|screenSize"
    android:label="@string/app_name"
    android:noHistory="true"
    android:screenOrientation="portrait" >
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>
<meta-data
    android:name="com.indooratlas.android.sdk.API_KEY"
    android:value="c24c139a-0fd8-4072-b92d-440f1369a413"/>
<meta-data
    android:name="com.indooratlas.android.sdk.API_SECRET"
        android:value="jU)0v5VVdUGfpE69DUS!zLmqVhA1wiPNymesYonp6XSArIshOSfYKbhJP9v6zIpdl8U9hOhrgQiPWYYjwSWUjgjDlbi44MNu0P52dwglirV0qTAWFfY7sj)ClhXp80i1"/>
</application>

apply plugin: 'com.android.application'

android {
compileSdkVersion 21
buildToolsVersion "21.1.2"

defaultConfig {
    applicationId "com.lightcurb.example"
minSdkVersion 18
targetSdkVersion 21
versionCode 9
versionName "1.0.0"
}
buildTypes {
    release {
    minifyEnabled false
    proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-         rules.pro'
        }
    }
}

repositories {
mavenCentral()
flatDir {
    dirs 'libs'
    }
}

dependencies {
compile 'com.indooratlas.android:indooratlas-android-sdk:2.0.2-beta@aar'
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.radiusnetworks:AndroidIBeaconLibrary:0.7.7@aar'
compile 'com.lightcurb.sdk:LightcurbSDK:1.0.1@aar'
}
repositories{
maven {
    url "http://indooratlas-ltd.bintray.com/mvn-public"
   }
}

gulp.task('watch', function() {
    gulp.watch('./src/**/*.js', ['js']);
});

gulp.task('watch', function() {
    gulp.watch('./src/*.js', ['js']);
    gulp.watch('./src/dir1/**/*.js', ['js']);
    gulp.watch('./src/dir2/**/*.js', ['js']);
});