在android studio中出现意外的顶级异常

我试图编写一个简单的Android应用程序，我收到此错误消息 . 请帮助

错误：任务'：app：dexDebug'的执行失败 .

com.android.ide.common.internal.LoggedErrorException：无法运行命令：D：\ Users \ user \ AppData \ Local \ Android \ sdk \ build-tools \ 21.1.2 \ dx.bat --dex --no -optimize --output C：\ Users \ user \ Desktop \ SocialNetworking \ app \ build \ intermediates \ dex \ debug --input-list = C：\ Users \ user \ Desktop \ SocialNetworking \ app \ build \ intermediates \ tmp \ dex \ debug \ inputList.txt错误代码：2输出：UNEXPECTED TOP-LEVEL EXCEPTION：com.android.dex.DexException：多个dex文件定义Lbolts / AggregateException;在com.android.dx.merge.DexMerger.readSortableTypes（DexMerger.java:596）在com.android.dx.merge.DexMerger.getSortedTypes（DexMerger.java:554）在com.android.dx.merge.DexMerger.mergeClassDefs （DexMerger.java:535）在com.android.dx.merge.DexMerger.mergeDexes（DexMerger.java:171）在com.android.dx.merge.DexMerger.merge（DexMerger.java:189）在com.android . dx.command.dexer.Main.mergeLibraryDexBuffers在com.android.dx.command.dexer.Main（Main.java:454）在com.android.dx.command.dexer.Main.runMonoDex（Main.java:303） . 在com.android.dx.command.Main.main（Main.java:106）的com.android.dx.command.dexer.Main.main（Main.java:215）运行（Main.java:246）

我的gradle构建如下

apply plugin: 'com.android.application'

android {
compileSdkVersion 21
buildToolsVersion "21.1.2"

defaultConfig {
    applicationId "jason.orchid.com.socialnetworking"
    minSdkVersion 19
    targetSdkVersion 21
    versionCode 1
    versionName "1.0"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}
repositories { mavenCentral() }

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:21.0.3'
compile 'com.android.support:support-v4:21.0.3'
compile 'com.parse.bolts:bolts-android:1.1.4'
compile 'com.facebook.android:facebook-android-sdk:3.23.0'
compile 'com.parse.bolts:bolts-android:1.+'
compile fileTree(dir: 'libs', include: 'Parse-*.jar')
}