안드로이드 개인플젝

2일차...
리스트를 누르면 음악재생 음악제목 앨범사진이 클릭한 음악에 맞게
출력되길 원했는데...
왠지모르지만 되긴함..왜 되는건지 이유를 모를뿐..

버튼으로 다음곡으로 넘어가기 도전했지만,,,실패

package com.example.recommend_music

import android.content.Context
import android.content.Intent
import android.media.MediaPlayer
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Environment
import android.os.SystemClock
import android.view.View
import android.widget.*
import androidx.core.app.ActivityCompat
import java.io.File
import java.text.SimpleDateFormat

class Music_play : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_music_play)
        var musicImg = findViewById<ImageView>(R.id.musicImag)
        var musictitle = findViewById<TextView>(R.id.musicTitle)
        var time1 = findViewById<TextView>(R.id.time1)
        var bar1 = findViewById<SeekBar>(R.id.bar1)
        var list = findViewById<ListView>(R.id.list1)
//        var btn1 = findViewById<Button>(R.id.btn4)
//        var btn2 = findViewById<ImageButton>(R.id.btn2)
//        var btn3 = findViewById<ImageButton>(R.id.btn3)

        var mp3List : ArrayList<String>
        var mp3Path = "/sdcard/"
        var selectmp3 :String
        var Imags = arrayOf(R.drawable.m_1,R.drawable.m_2,R.drawable.m_3)
        musicImg.setImageResource(Imags[0])

        mp3List = ArrayList()
        var listFiles = File(mp3Path).listFiles()

        var fileName:String
        var extName:String

        for(file in listFiles!!){
            fileName = file.name      //파일이름

            if (!file.isDirectory){
                extName = fileName.substring(fileName.length-3)
                if (extName =="mp3"){
                    mp3List.add(fileName)
                }
            }
        }

        var index = mp3List.size

        var adapter = ArrayAdapter(this,android.R.layout.simple_list_item_1,mp3List)
        list.adapter = adapter

        var mPlayer = MediaPlayer()
        list.setOnItemClickListener { parent, view, position, id ->
            musicImg.setImageResource(Imags[position])
            selectmp3 = mp3List[position]
            musictitle.text = "$selectmp3"
            mPlayer.isLooping=true

            if (mPlayer.isPlaying == false){
                mPlayer.setDataSource(mp3Path + selectmp3)  //음악 경로임
                mPlayer.prepare()
                mPlayer.start()
            }
            else{
                mPlayer.stop()
                time1.text = "재생시간 :"
                mPlayer.reset()
            }

            object :Thread(){
                var timeFormat = SimpleDateFormat("mm:ss")
                override fun run() {
                    super.run()
                    if (mPlayer ==null){
                        return
                    }
                    bar1.max = mPlayer.duration
                    while (mPlayer.isPlaying){
                        runOnUiThread {
                            bar1.progress =mPlayer.currentPosition
                            time1.text = "재생시간 : "+timeFormat.format(mPlayer.currentPosition)
                        }
                        SystemClock.sleep(200)
                    }
                }
            }.start()
        }


        //음악 멈춤 reset을해줘야 리스트를 다시 누를때 음악나옴....아님 터짐 이거때문에......별거아닌건데 왜 한참찾은거지
//        btn2.setOnClickListener {
//            mPlayer.stop()
//            mPlayer.reset()
//        }
    }
}