通过这个字段

 ${project.rootProject.projectDir}";

如项目根build.gradle中：

// Top-level build file where you can add configuration options common to all sub-projects/modules.buildscript {repositories {google()mavenCentral()// jcenter() // keeped as anchor, will be removed soon}dependencies {classpath 'com.android.tools.build:gradle:8.0.2'// NOTE: Do not place your application dependencies here; they belong// in the individual module build.gradle files}ext {// 定义全局变量，常用于版本管理// 变量在子模块的build.gradle中直接以： $NAME 的形式调用RootProjectDir = "${project.rootProject.projectDir}".replace("\\", "/")}
}apply from: NATIVE_DIR +"/build.gradle"

app的build.gradle中：

android {defaultConfig {...}...println  "Root project2:   ${RootProjectDir}";
}

输出：