Integrerate Spark Streaming and Kafka, but get bad symbolic reference error - scala

Question

I am trying to integrate Spark streaming and Kafka. I wrote my source code in intellij idea IDE; the complier compiled the code without any error, but when I try to build the jar file, an error message is generated that shows:
Error:scalac: bad symbolic reference. A signature in KafkaUtils.class
refers to term kafka in package which is not available. It may
be completely missing from the current classpath, or the version on
the classpath might be incompatible with the version used when
compiling KafkaUtils.class.
I did research on google, many people say this is because of different versions between Scala version and spark_streaming_kafka jar file. But I have checked the version, they are the same.
Does someone know why this error happened?
Here are more details:
scala version : 2.10
spark streaming kafka jar version : spark_streaming_kafka_2.10-1.20.jar,spark_streaming_2.10-1.20.jar
My source code:
object Kafka {
def main(args: Array[String]) {
val master = "local[*]"
val zkQuorum = "localhost:2181"
val group = ""
val topics = "test"
val numThreads = 1
val conf = new SparkConf().setAppName("Kafka")
val ssc = new StreamingContext(conf, Seconds(2))
val topicpMap = topics.split(",").map((_, numThreads.toInt)).toMap
val lines = KafkaUtils.createStream(ssc, zkQuorum, group, topicpMap).map(_._2)
val words = lines.flatMap(_.split(" "))
words.print()
ssc.start()
ssc.awaitTermination()
}
}