托盘分级插件未上载工件

我使用bintray gradle插件在bintray上上传java工件。我从示例中编写了这段代码,它成功地创建了包和版本,但files目录中并没有文件。我这里遗漏了什么??

bintray {
    user = 'user name'
    key = 'my key'
    pkg {
        repo = 'androids'
        name = 'name'
        licenses = ['Apache-2.0']
        vcsUrl = 'https://github.com/bintray/gradle-bintray-plugin.git'
        version {
            name = 'version'
            desc = 'Gradle Bintray Plugin 1.0 final'
            released  = new Date()
            vcsTag = '1.3.0'
            attributes = ['gradle-plugin': 'com.use.less:com.use.less.gradle:gradle-useless-plugin']
        }

        filesSpec {
            from 'build/libs'
            into 'standalone_files/level1'
        }
    }

}