Unresolved reference when using a local jar in kotlin project

i am not good at english,so i use google translate for help.hope my meaning can be expressed clearly.

I am trying to import a jarfile which is created by myself in my project.I build a gradle project(kotlin jvm),add my local jar into gradle.build,find it in the <External Libraries>,but when i tried to import my classes,i got a "Unresolved reference" error,however,i can run my code.how can i fix it?many thx