Gradle build error in comman line for Android Studio app projects

I saw someone met the same problem on StackOverflow. Fortunately,  I found out how to make it work. So leave some notes here:
1. upgrade Gradle version to 1.6
2. Afterward, running "gradle build --stacktrace", you will see that ANDROID_HOME environment variable is required to be set up.
3. on Mac, add following line to your ~/.bash_profile
export ANDROID_HOME="/Applications/Android Studio.app/sdk/"

Now it should work like a charm!