Why my activity can't import DaoMaster.java gennerated by greendao

I created by this post,I genarate the Entity,Dao,DaoMaster and DaoSession ,but I can't import these class? How can I do this?My android project has a java module in android studio,I generated the src-gem in my android project,and I can't add the src folder as java sources folder.

build.gradle

android {

    sourceSets {
        main {
            java.srcDirs = ['src/main/java','src-gem']
        }
    }
}

It's work.