강의를 듣고 응용해봤는데 질문있습니다

강의의 게시판 만들기 부분을 실습하고 나서 게시글 양식으로 만드셨던 board_list_item.xml을 이렇게 변경해봤습니다. 나머지 글들은 강의에서 하던대로 따라해서 불러와지는게 되는데 제가 추가한 저 초록색사진은 글을 작성할때 즉 강의 상의 코드인 BoardWriteActivity.kt에서 사진이 첨부되면 그 첨부된 사진이 저 초록색사진에 같이 업로드 되게끔 만들고 싶습니다. 저 사진의 id값은 preview입니다.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".Sell">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="?attr/colorPrimary"
            android:minHeight="?attr/actionBarSize"
            android:theme="?attr/actionBarTheme"
            app:titleTextColor="@color/white"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="판매글 작성"
                android:textSize="23sp"
                android:textStyle="bold"/>
        </androidx.appcompat.widget.Toolbar>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:orientation="vertical">

            <EditText
                android:id="@+id/et_newtitle"
                android:layout_width="330dp"
                android:layout_height="50dp"
                android:layout_marginLeft="20dp"
                android:layout_marginTop="70dp"
                android:gravity="center"
                android:maxLength="15" />

            <EditText
                android:id="@+id/et_originalname"
                android:layout_width="330dp"
                android:layout_height="50dp"
                android:layout_marginLeft="20dp"
                android:layout_marginTop="20dp"
                android:gravity="center"
                android:hint="※주의 : 책 제목 그대로 써주세요 ※"
                android:maxLength="100" />

            <EditText
                android:id="@+id/et_price"
                android:layout_width="330dp"
                android:layout_height="50dp"
                android:hint="숫자 옆에 원을 붙여주세요"
                android:layout_marginLeft="20dp"
                android:layout_marginTop="20dp"
                android:gravity="center"
                android:maxLength="10" />

            <ImageView
                android:id="@+id/imageupload"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:src="@drawable/baseline_add_black_48dp"
                android:layout_marginTop="30dp"
                />

            <EditText
                android:id="@+id/et_newdetail"
                android:layout_width="334dp"
                android:layout_height="260dp"
                android:layout_marginLeft="20dp"
                android:layout_marginTop="30dp"
                android:layout_marginBottom="10dp"
                android:background="@drawable/boxline"
                android:ems="10"
                android:gravity="top"
                android:hint="내용을 입력하세요."
                android:maxHeight="200dp"
                android:maxLength="200" />

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="96dp"
                android:layout_marginBottom="60dp"
                android:gravity="center"
                android:orientation="horizontal"
                android:paddingTop="30dp">

                <Button
                    android:id="@+id/upload"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginRight="50dp"
                    android:text="올리기" />

                <Button
                    android:id="@+id/cancel"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="취소" />

            </LinearLayout>

        </LinearLayout>

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:id="@+id/newtitle"
                android:layout_width="35dp"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="90dp"
                android:text="제목"
                android:textSize="16sp" />

            <TextView
                android:id="@+id/newname"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="12dp"
                android:layout_marginTop="160dp"
                android:text="상품명"
                android:textSize="15sp" />

            <TextView
                android:id="@+id/price"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="10dp"
                android:layout_marginTop="235dp"
                android:text="판매가격"
                android:textSize="13sp" />

            <TextView
                android:id="@+id/newpicture"
                android:layout_width="35dp"
                android:layout_height="17dp"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="300dp"
                android:text="사진"
                android:textSize="16sp" />

            <TextView
                android:id="@+id/newdetail"
                android:layout_width="35dp"
                android:layout_height="28dp"
                android:layout_marginLeft="15dp"
                android:layout_marginTop="370dp"
                android:text="내용"
                android:textSize="16sp" />

        </FrameLayout>

    </FrameLayout>



</ScrollView>

package com.example.joonggo2

import android.content.Intent
import android.graphics.Bitmap
import android.graphics.drawable.BitmapDrawable
import android.net.Uri
import android.os.Bundle
import android.provider.MediaStore
import android.util.Log
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.bumptech.glide.Glide
import com.example.joonggo2.databinding.ActivityBoardInsideBinding
import com.example.joonggo2.databinding.ActivityMainBinding
import com.example.joonggo2.databinding.ActivityMifBinding
import com.example.joonggo2.databinding.ActivitySellBinding
import com.google.firebase.ktx.Firebase
import com.google.firebase.storage.ktx.storage
import java.io.ByteArrayOutputStream


class Sell : AppCompatActivity() {
    private lateinit var binding: ActivitySellBinding
    private val TAG = Sell::class.java.simpleName
    val storage = Firebase.storage
    private var isImageUpload = false



    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivitySellBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.upload.setOnClickListener{
            val title = binding.etNewtitle.text.toString()
            val originalname = binding.etOriginalname.text.toString()
            val price = binding.etPrice.text.toString()
            val content = binding.etNewdetail.text.toString()
            val uid = FBAuth.getUid()
            val time = FBAuth.getTime()

            Log.d(TAG, title)
            Log.d(TAG, content)

            val key = FBRef.writein.push().key.toString()

            FBRef.writein
                .child(key)
                .setValue(BoardModel(title, originalname, price, content, uid, time))

            Toast.makeText(this,"게시물이 업로드 되었습니다.", Toast.LENGTH_LONG).show()

            if(isImageUpload == true) {
                imageUpload(key)
            }



            val intent = Intent(this, AfterLoginmain::class.java)
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
            startActivity(intent)

        }

        binding.cancel.setOnClickListener {
        val intent = Intent(this, AfterLoginmain::class.java)
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
            startActivity(intent)



        }

        binding.imageupload.setOnClickListener {
            val gallery = Intent(Intent.ACTION_PICK, MediaStore.Images.Media.INTERNAL_CONTENT_URI)
            startActivityForResult(gallery, 100)
            isImageUpload = true
        }

    }

    private fun imageUpload(key : String) {
// Get the data from an ImageView as bytes
        val storageRef = storage.reference
        val mountainsRef = storageRef.child(key + ".png")
        val imageView = binding.imageupload
        imageView.isDrawingCacheEnabled = true
        imageView.buildDrawingCache()
        val bitmap = (imageView.drawable as BitmapDrawable).bitmap
        val baos = ByteArrayOutputStream()
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos)
        val data = baos.toByteArray()

        var uploadTask = mountainsRef.putBytes(data)
        uploadTask.addOnFailureListener {
            // Handle unsuccessful uploads
        }.addOnSuccessListener { taskSnapshot ->
            // taskSnapshot.metadata contains file metadata such as size, content-type, etc.
            // ...
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if(resultCode == RESULT_OK && requestCode == 100) {
            binding.imageupload.setImageURI(data?.data)
        }
    }
}

위 사진두개는 강의에서 하신 BoardWriteActivity.kt와 역할이 같은 xml과 kt파일입니다. 지금 이 코드에서 글과 갤러리에서 사진을 첨부하는 기능은 모두 구현되어있습니다. 그런데 사진도 메인화면에 뜨게끔 하려니 너무 막막해서 질문드립니다...