파이어베이스 realtime datatbase 데이터에 안뜹니다.

안녕하세요. firebase 데이터 추가 강의 듣고 있습니다.

실행에 오류는 없는데 눌러도 데이터에 변화가 없습니다.

class ContentListActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_content_list)

        // Write a message to the database
        val database = Firebase.database
        val myRef = database.getReference("contents")

        myRef.push().setValue(
            ContentModel("title1", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2FblYPPY%2Fbtq66v0S4wu%2FRmuhpkXUO4FOcrlOmVG4G1%2Fimg.png", "https://philosopher-chan.tistory.com/1235?category=941578")
        )
        myRef.push().setValue(
            ContentModel("title2", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2FznKK4%2Fbtq665AUWem%2FRUawPn5Wwb4cQ8BetEwN40%2Fimg.png", "https://philosopher-chan.tistory.com/1236?category=941578")
        )
        myRef.push().setValue(
            ContentModel("title3", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2Fbtig9C%2Fbtq65UGxyWI%2FPRBIGUKJ4rjMkI7KTGrxtK%2Fimg.png", "https://philosopher-chan.tistory.com/1237?category=941578")
        )

        val rv : RecyclerView = findViewById(R.id.rv) //리사이클 뷰 생성
        // 데이터 삽입
        val items = ArrayList<ContentModel>()
        items.add(ContentModel("title1", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2FblYPPY%2Fbtq66v0S4wu%2FRmuhpkXUO4FOcrlOmVG4G1%2Fimg.png", "https://philosopher-chan.tistory.com/1235?category=941578"))
        items.add(ContentModel("title2", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2FznKK4%2Fbtq665AUWem%2FRUawPn5Wwb4cQ8BetEwN40%2Fimg.png", "https://philosopher-chan.tistory.com/1236?category=941578"))
        items.add(ContentModel("title3", "https://img1.daumcdn.net/thumb/R1280x0/?scode=mtistory2&fname=https%3A%2F%2Fblog.kakaocdn.net%2Fdn%2Fbtig9C%2Fbtq65UGxyWI%2FPRBIGUKJ4rjMkI7KTGrxtK%2Fimg.png", "https://philosopher-chan.tistory.com/1237?category=941578"))

        val rvAdapter = ContentRVAdapter(baseContext, items) //어뎁터 생성
        rv.adapter = rvAdapter

        rv.layoutManager = GridLayoutManager(this, 2)


        rvAdapter.itemClick = object : ContentRVAdapter.ItemClick{
            override fun onClick(view: View, position: Int) {

                Toast.makeText(baseContext, items[position].title, Toast.LENGTH_LONG).show()

                val intent = Intent(this@ContentListActivity, ContentShowActivity::class.java)

                //url 넘겨주기
                intent.putExtra("url", items[position].webUrl)
                startActivity(intent)
            }
        }
    }
}