我终于找到了问题所在.该项目使用 Android Annotations，我已将其生成的源文件夹包含在我的 build.gradle 文件中.

I finally found out what the problem was. The project uses Android Annotations, and I had included its generated sources folder in my build.gradle file.

当 Gradle 再次尝试生成源时，会因为类重复而失败.

When Gradle tried to generate the sources again, it would fail because of the duplicated classes.

这是正确的 build.gradle:

Here's the correct build.gradle:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}
apply plugin: 'android'

dependencies {
    compile fileTree(dir: 'libs/main', include: '*.jar')
    compile project(':Libraries:LibProject1')
    compile project(':Libraries:LibProject2')
    compile project(':Libraries:LibProject3')
    compile project(':Libraries:LibProject4')
}

android {
    compileSdkVersion "Google Inc.:Google APIs:19"
    buildToolsVersion "19.0.1"

    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src/main/java', 'src-gen/main/java']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
        }
    }
}