hi FatmingWang2,
you could add your lib by Project Properties> linker.
add lib directory to Project Properties>Linker> General>Additional Library Directories
add the lib to Project Properties>Linker>Input>Additional Dependencies.
It might be possible that you’re linking against two different STLs at once. I’ve successfully used the GPG library in the Hello World Demo project with the following settings:
C/C++ → General → Additional Include Directories = \android\include
Linker → General → Additional Library Directories = \android\lib\gnustl\armeabi-v7a
Linker → Input → Additional Dependencies = gpg;z
Note that I’m using the prebuilt library from the gnustl folder because my General → STL Type property is set by default to GNU libstdc++ Static.