"sources.mk" not updated after import existed directory

[jack_zmh]

Hello, I started a project from an imported SDK example with MCUXpresso V10.3. It was been built successfully before I added exist source files. After adding some exist source files in to the project by Import-->Files System, I meet the problem "undefined reference to xxx". I have added referred directory in "Include paths". I checked "sources.mk", in the SUBDIRS section, the referred directory named "CANopen" isn't included. How can I  manage this?

[jack_zmh · Accepted solution]

I have solved this problem by converting "folder" to "source folder" after search on google.

"In order to do this in Eclipse, you should get in your project's properties, then expand C/C++ general -> Paths and Symbols -> Sources tab. Then click the Add Folder button, and choose the normal folders you wish to include as "source folders."