Hi Aankin_wang,
According to ROS community support guidelines Support - ROS Wiki this question should be better asked in http://answers.ros.org
Please do not post questions on the discourse.ros.org they should go to ROS Answers.
ROS Discourse is for news and general interest discussions. ROS Answers provides a forum which can be filtered by tags to make sure the relevant people are included and not overload everyone.
Best regards,
Martin