서비스로 안드로이드 뮤직 플레이어 UI에

Question

안드로이드에 음악 플레이어 코드를 쓰려고했습니다. 노래, 아티스트 및 앨범 이미지의 현재 제목을 표시하려고합니다. 활동 내역 : package com.example.getmusic;

import java.io.IOException; 
import java.util.ArrayList; 


import com.example.getmusic.PlayMusicService.LocalBinder; 




import android.media.AudioManager; 
import android.media.MediaMetadataRetriever; 
import android.media.MediaPlayer; 
import android.media.MediaPlayer.OnCompletionListener; 
import android.media.MediaPlayer.OnPreparedListener; 
import android.net.Uri; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.os.Handler; 
import android.os.IBinder; 
import android.provider.MediaStore; 
import android.provider.MediaStore.Audio; 
import android.app.Activity; 
import android.content.BroadcastReceiver; 
import android.content.ComponentName; 
import android.content.Context; 
import android.content.Intent; 
import android.content.ServiceConnection; 
import android.content.res.Configuration; 
import android.database.Cursor; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.telephony.TelephonyManager; 
import android.util.Log; 
import android.view.GestureDetector; 
import android.view.GestureDetector.OnGestureListener; 
import android.view.Menu; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.ImageView; 
import android.widget.SeekBar; 
import android.widget.TextView; 
import android.widget.Toast; 
import android.widget.SeekBar.OnSeekBarChangeListener; 

public class GetMusic extends Activity implements OnGestureListener { 
     static Handler seekhandler=new Handler(); 
     boolean isServiceConnected=false; 
     PlayMusicService playServ; 
    static TextView tv1,tv2,tv3; 
    Button previous,next;static ImageView img;static GestureDetector gDetector; 
    int pausePressed=1;static SeekBar sb; 

    int currentIndex=0;Cursor cursor;GenericSongClass GSC; 
    static MediaPlayer mediaPlayer;static int posofaudiotrack; 
    private ServiceConnection conn=new ServiceConnection() { 

     @Override 
     public void onServiceDisconnected(ComponentName name) { 
      // TODO Auto-generated method stub 
      isServiceConnected=false; 
     } 

     @Override 
     public void onServiceConnected(ComponentName name, IBinder service) { 
      // TODO Auto-generated method stub 

    LocalBinder binder=(LocalBinder)service; 
    playServ=binder.getService(); 
    isServiceConnected=true; 

     } 
    }; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_get_music); 
     gDetector= new GestureDetector(this); 
     tv1=(TextView)findViewById(R.id.textView1); 
     tv2=(TextView)findViewById(R.id.textView2); 
     tv3=(TextView)findViewById(R.id.textView3); 
     getSongs(); 

     img=(ImageView)findViewById(R.id.imageView1); 
     sb=(SeekBar)findViewById(R.id.seekBar1); 
     try{ 
     Intent serv = new Intent(this,PlayMusicService.class); 

      bindService(serv, conn, Context.BIND_AUTO_CREATE); 
     System.out.println("in try calling service"); 
     startService(serv); 
     } 
     catch(Exception e){ 
      System.out.println("Exception is"+e); 
     } 
     System.out.println("after binding"); 
     /* 
     try { 
      playSong(0); 


    } 
     catch(Exception e){ 
     System.out.println("Exception is"+e); 
    }*/ 
     //PlayMusic p=new PlayMusic(); 
     // p.execute(); 

    } 


    @Override 
    protected void onStop() { 
     // TODO Auto-generated method stub 
     super.onStop(); 
     if (isServiceConnected) { 
       unbindService(conn); 
       isServiceConnected = false; 
      } 
    } 


    public static void mediaPlayerPause() 
    { 

     if(mediaPlayer!=null) 
     { 

      mediaPlayer.pause(); 
      posofaudiotrack=mediaPlayer.getCurrentPosition(); 
     } 

    } 
    public void mediaPlayerResume() 
    { 

     if(mediaPlayer!=null&&!mediaPlayer.isPlaying()) 
     { 
      mediaPlayer.seekTo(mediaPlayer.getCurrentPosition()); 
      mediaPlayer.start(); 
     } 
    } 
    public class PlayMusic extends AsyncTask<Void, Void, Void> 
    { 

     @Override 
     protected Void doInBackground(Void... params) { 
      // TODO Auto-generated method stub 
      getSongs(); 
      return null; 
     } 

    } 
    @Override 
    public void onConfigurationChanged(Configuration newConfig) { 
     // TODO Auto-generated method stub 
     super.onConfigurationChanged(newConfig); 
    } 

    public static ArrayList<GenericSongClass> songs = null; 

    public void getSongs() {   

     Toast.makeText(getApplicationContext(), "in BindAllSongs()", Toast.LENGTH_SHORT).show(); 
      String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0"; 
      final String[] projection = new String[] { 
        MediaStore.Audio.Media.DISPLAY_NAME, 
        MediaStore.Audio.Media.ARTIST, 

        MediaStore.Audio.Media.DATA,MediaStore.Audio.Media.COMPOSER,MediaStore.Audio.Media.TITLE,MediaStore.Audio.Media.ALBUM 
        }; 
        final String sortOrder = MediaStore.Audio.AudioColumns.TITLE 
          + " COLLATE LOCALIZED ASC"; 

        try { 

         Uri uri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI; 


         cursor = getBaseContext().getContentResolver().query(uri, 
           projection, selection, null, sortOrder); 
        /* int column_index = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA); 
         String s=cursor.getString(column_index);*/ 
         // Toast.makeText(getApplicationContext(), "path is"+s, Toast.LENGTH_SHORT).show(); 
         // System.out.println("path is"+s); 


         if (null == cursor) { 
          Log.e("error","cursor is null"); 
         // If the Cursor is empty, the provider found no matches 
         } else if (cursor.getCount() < 1) { 

          Log.i("info","cursor count<1"); 
         } else { 



          songs = new ArrayList<GenericSongClass>(cursor.getCount()); 
          cursor.moveToFirst(); 
          int colIndex=cursor.getColumnIndex(MediaStore.Audio.Media.DATA); 
          String path = cursor.getString(colIndex); 
          // Toast.makeText(getApplicationContext(), "PATH IS"+path, Toast.LENGTH_SHORT).show(); 
          System.out.println("PATH IS"+path); 
          while (!cursor.isAfterLast()) { 
           GSC = new GenericSongClass(); 
           GSC.songTitle = cursor.getString(0); 
           GSC.songArtist = cursor.getString(1); 
           GSC.songData = cursor.getString(2); 
           GSC.songComposer=cursor.getString(3); 
           GSC.title=cursor.getString(4); 
           GSC.album=cursor.getString(5); 

           songs.add(GSC); 
           cursor.moveToNext(); 

          } 


         // Toast.makeText(getApplicationContext(), "songs first is"+songs.get(0).songTitle, Toast.LENGTH_SHORT).show(); 
         // Toast.makeText(getApplicationContext(), "songs length is"+songs.size(), Toast.LENGTH_SHORT).show(); 
          mediaPlayer=new MediaPlayer(); 
          mediaPlayer.setOnPreparedListener(new OnPreparedListener() { 

           @Override 
           public void onPrepared(MediaPlayer mp) { 
            // TODO Auto-generated method stub 
            Log.e("I", "Media player has been loaded to memory !"); 
           } 
          }); 
          /*for(int i=0;i<songs.size();i++){ 
           if(mediaPlayer.isPlaying()) 
            mediaPlayer.reset(); 
           String p=songs.get(i).songData; 
           mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);*/ 


         } 
        } 
         catch (Exception ex) { 
         Toast.makeText(getApplicationContext(), "exception is"+ex, Toast.LENGTH_SHORT).show(); 
         Log.i("ex is",ex.toString()); 
        } finally { 
         if (cursor != null) { 
          cursor.close(); 
         }} 
        } 



    protected void getPreviousSong() 
    { 

     if(currentIndex==0) 
      currentIndex=songs.size()-1; 
     else{ 
      currentIndex=currentIndex-1; 
      } 
     playSong(currentIndex); 
    } 
    protected void getNextSong() { 
     // TODO Auto-generated method stub 

     if(currentIndex == songs.size()-1){ 
      currentIndex=0; 

     } 
     else 
     { 
      currentIndex=currentIndex+1; 


     } 
     playSong(currentIndex); 
    } 
    private void playSong(int index) { 
     // TODO Auto-generated method stub 
     try{ 
      mediaPlayer.reset(); 
      String p=songs.get(index).songData; 
     System.out.println("Song title is"+songs.get(1).songTitle+"artist"+songs.get(1).songArtist+"composer is"+songs.get(1).songComposer.valueOf(0)+"title is"+songs.get(1).title); 
     mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC); 
     tv1.setText(songs.get(index).title); 
     tv2.setText(songs.get(index).album); 
     tv3.setText(songs.get(index).songArtist); 
    // tv3.append(songs.get(index).album); 
     mediaPlayer.setDataSource(p); 
     MediaMetadataRetriever mmr = new MediaMetadataRetriever(); 
     byte[] rawArt; 
     Bitmap art = null; 
     BitmapFactory.Options bfo=new BitmapFactory.Options(); 
     mmr.setDataSource(p); 

     rawArt = mmr.getEmbeddedPicture(); 



     if (null != rawArt) 
      art = BitmapFactory.decodeByteArray(rawArt, 0, rawArt.length, bfo); 
     img.setImageBitmap(art); 
     } catch (IllegalArgumentException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show();; 
     } catch (SecurityException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IllegalStateException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
      Log.d("exc","exception is"+e.toString()); 
      System.out.println("exception is"+e.toString()); 
     } 
     try { 
      mediaPlayer.prepare(); 
     } catch (IllegalStateException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "prepate exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "prepate exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
      System.out.println("exception is"+e.toString()); 
     } 

     mediaPlayer.start(); 
     sb.setMax(mediaPlayer.getDuration()); 
     seekUpdation(); 
sb.setOnSeekBarChangeListener(new OnSeekBarChangeListener() { 

      @Override 
      public void onStopTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 
      seekhandler.removeCallbacks(run); 
      mediaPlayer.seekTo(seekBar.getProgress()); 
      seekhandler.postDelayed(run, 1000); 
      } 

      @Override 
      public void onStartTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 
       seekhandler.removeCallbacks(run); 

      } 

      @Override 
      public void onProgressChanged(SeekBar seekBar, int progress, 
        boolean fromUser) { 
       // TODO Auto-generated method stub 

      } 
     }); 
     mediaPlayer.setOnCompletionListener(new OnCompletionListener() { 

      @Override 
      public void onCompletion(MediaPlayer mediaPlayer) { 
       // TODO Auto-generated method stub 
       pausePressed=1; 
       playServ.getNextSong(); 

      } 
     }); 

        } 



    Runnable run = new Runnable() { 

      @Override 
      public void run() { 
       seekUpdation(); 
      } 
     }; 


     public void seekUpdation() { 

      sb.setProgress(mediaPlayer.getCurrentPosition()); 
      seekhandler.postDelayed(run, 1000); 
     } 
    public class GenericSongClass { 

      String songTitle = ""; 
      String songArtist = ""; 
      String songData = ""; 
      String songComposer=""; 
      String title=""; 
      String album=""; 
      String isChecked = "false"; 
    } 



    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.get_music, menu); 
     return true; 
    } 

    @Override 
    public boolean onDown(MotionEvent e) { 
     // TODO Auto-generated method stub 
     return false; 
    } 

    @Override 
    public boolean onTouchEvent(MotionEvent me) { 
    return gDetector.onTouchEvent(me); 
    } 
    @Override 
    public boolean onFling(MotionEvent start, MotionEvent finish, float velocityX, 
      float velocityY) { 
     pausePressed=1;//int x=playServ.getCurrentIndex(); 
     // TODO Auto-generated method stub 
     if(start.getRawX() < finish.getRawX()) 
     { 
      //Toast.makeText(getApplicationContext(), "chanegd", Toast.LENGTH_SHORT).show(); 
      if(playServ!=null){ 

      /* if(x==0) 
        x=songs.size()-1; 
       else{ 
        x=currentIndex-1; 
        } 
        tv1.setText(songs.get(x).title); 
        tv2.setText(songs.get(x).album); 
        tv3.setText(songs.get(x).songArtist); 
       tv3.append(songs.get(x).album);*/ 

      playServ.getPreviousSong();} 
      else 
       System.out.println("ms null"); 
     } 
     else if(start.getRawX()>finish.getRawX()) 
     { 
      //Toast.makeText(getApplicationContext(), "changed on other", Toast.LENGTH_SHORT).show(); 

      Log.d("onFLing","in onFling"); 
      if(playServ!=null){ 
       /* 
       if(x == songs.size()-1){ 
        x=0; 

       } 
       else 
       { 
        x=x+1; 


       } 
        tv1.setText(songs.get(x).title); 
        tv2.setText(songs.get(x).album); 
        tv3.setText(songs.get(x).songArtist); 
       tv3.append(songs.get(x).album);*/ 
      playServ.getNextSong(); 
      } 
      else 
       System.out.println("ms null"); 
     } 
     return true; 

    } 

    @Override 
    public void onLongPress(MotionEvent e) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, 
      float distanceY) { 
     // TODO Auto-generated method stub 
     return false; 
    } 

    @Override 
    public void onShowPress(MotionEvent e) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public boolean onSingleTapUp(MotionEvent e) { 
     // TODO Auto-generated method stub 
    System.out.println("PAUSEPRESSED"+pausePressed); 
     if(pausePressed==1){ 
      pausePressed=0; 
      playServ.mediaPlayerPause(); 
     }else if(pausePressed==0){ 
      pausePressed=1; 


       //mediaPlayer.seekTo(posofaudiotrack); 
       playServ.mediaPlayerResume(); 


     } 
     return true; 
    } 

} 
and the Service is: 
package com.example.getmusic; 

import java.io.IOException; 
import java.util.ArrayList; 

import com.example.getmusic.GetMusic.GenericSongClass; 

import android.app.Service; 
import android.content.Intent; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.media.AudioManager; 
import android.media.MediaMetadataRetriever; 
import android.media.MediaPlayer; 
import android.media.MediaPlayer.OnCompletionListener; 
import android.media.MediaPlayer.OnPreparedListener; 
import android.os.Binder; 
import android.os.IBinder; 
import android.util.Log; 
import android.widget.SeekBar; 
import android.widget.Toast; 
import android.widget.SeekBar.OnSeekBarChangeListener; 

public class PlayMusicService extends Service{ 
    MediaPlayer mp;int currentIndex=0; 
    ArrayList<GenericSongClass> songs=GetMusic.songs;int pausePressed=1; 
    IBinder servbind=new LocalBinder(); 
    public class LocalBinder extends Binder{ 
     PlayMusicService getService() 
     { 
      return PlayMusicService.this; 
     } 
    } 
    @Override 
    public IBinder onBind(Intent arg0) { 
     // TODO Auto-generated method stub 
     return servbind; 
    } 


    @Override 
    public void onCreate() { 
     // TODO Auto-generated method stub 
     super.onCreate(); 
     mp=new MediaPlayer(); 
     mp.setOnPreparedListener(new OnPreparedListener() { 

      @Override 
      public void onPrepared(MediaPlayer arg0) { 
       // TODO Auto-generated method stub 
       System.out.println("in onPrepared"); 
      } 
     }); 
mp.setOnCompletionListener(new OnCompletionListener() { 

      @Override 
      public void onCompletion(MediaPlayer mediaPlayer) { 
       // TODO Auto-generated method stub 
       pausePressed=1; 
       getNextSong(); 
      } 
     }); 
mp.setAudioStreamType(AudioManager.STREAM_MUSIC); 
try{ 
     System.out.println("in try"); 
     playSong(0); 
} 
catch(Exception e){ 
     System.out.println("in catch and exception is "+e.getMessage()); 
} 

    } 

    public void playSong(int index){ 

     // TODO Auto-generated method stub 
     try{ 
      System.out.println("in playsong"); 
      mp.reset(); 
      String p=songs.get(index).songData; 
     System.out.println("Song title is"+songs.get(1).songTitle+"artist"+songs.get(1).songArtist+"composer is"+songs.get(1).songComposer.valueOf(0)+"title is"+songs.get(1).title); 
     mp.setAudioStreamType(AudioManager.STREAM_MUSIC); 
    GetMusic.tv1.setText(songs.get(index).title); 
GetMusic.tv2.setText(songs.get(index).album); 
    GetMusic.tv3.setText(songs.get(index).songArtist); 
    GetMusic.tv3.append(songs.get(index).album); 
     mp.setDataSource(p); 
     MediaMetadataRetriever mmr = new MediaMetadataRetriever(); 
     byte[] rawArt; 
     Bitmap art = null; 
     BitmapFactory.Options bfo=new BitmapFactory.Options(); 
     mmr.setDataSource(p); 

     rawArt = mmr.getEmbeddedPicture(); 



     if (null != rawArt) 
      art = BitmapFactory.decodeByteArray(rawArt, 0, rawArt.length, bfo); 
    GetMusic.img.setImageBitmap(art); 
     } catch (IllegalArgumentException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show();; 
     } catch (SecurityException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IllegalStateException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
      Log.d("exc","exception is"+e.toString()); 
      System.out.println("exception is"+e.toString()); 
     } 
     try { 
      mp.prepare(); 
     } catch (IllegalStateException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "prepate exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      Toast.makeText(getApplicationContext(), "prepate exception is"+e.toString(), Toast.LENGTH_SHORT).show(); 
      System.out.println("exception is"+e.toString()); 
     } 

     mp.start(); 
     GetMusic.sb.setMax(mp.getDuration()); 
     seekUpdation(); 
GetMusic.sb.setOnSeekBarChangeListener(new OnSeekBarChangeListener() { 

      @Override 
      public void onStopTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 
      GetMusic.seekhandler.removeCallbacks(run); 
      mp.seekTo(seekBar.getProgress()); 
      GetMusic.seekhandler.postDelayed(run, 1000); 
      } 

      @Override 
      public void onStartTrackingTouch(SeekBar seekBar) { 
       // TODO Auto-generated method stub 
       GetMusic.seekhandler.removeCallbacks(run); 

      } 

      @Override 
      public void onProgressChanged(SeekBar seekBar, int progress, 
        boolean fromUser) { 
       // TODO Auto-generated method stub 

      } 
     }); 



    } 
    Runnable run = new Runnable() { 

      @Override 
      public void run() { 
       seekUpdation(); 
      } 
     }; 
    public void seekUpdation() { 

      GetMusic.sb.setProgress(mp.getCurrentPosition()); 
      GetMusic.seekhandler.postDelayed(run, 1000); 
     } 
    public int getCurrentIndex(){ 
     return currentIndex; 
    } 

    public void mediaPlayerPause() 
    { 

     if(mp!=null) 
     { 

      mp.pause(); 
      //pos=mediaPlayer.getCurrentPosition(); 
     } 

    } 
    public void mediaPlayerResume() 
    { 

     if(mp!=null&&!mp.isPlaying()) 
     { 
      mp.seekTo(mp.getCurrentPosition()); 
      mp.start(); 
     } 
    } 
    public void getPreviousSong() 
    { 

     if(currentIndex==0) 
      currentIndex=songs.size()-1; 
     else{ 
      currentIndex=currentIndex-1; 
      } 
     playSong(currentIndex); 
    } 
    public void getNextSong() { 
     // TODO Auto-generated method stub 

     if(currentIndex == songs.size()-1){ 
      currentIndex=0; 
     } 
     else 
     { 
      currentIndex=currentIndex+1; 


     } 
     playSong(currentIndex); 
    } 


    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) 
    { 
     mp.start(); 

     return 0; 

    } 

    @Override 
    public void onDestroy() 
    { 
     mp.release();  
     super.onDestroy(); 

    } 

} 

문제는 잘못 보여주는 것이 코드 UI.But에, 타이틀 곡을 보여주고 싶은 이미지를 가끔 잘 놀고, 때로는 그것을 중지하는 것 우리가 버튼을 다시 누르면 또는 홈 screen.I에 다른 애플 리케이션을 강타하다 일부 이미지는 이미지가 존재하더라도 이미지를 표시하지 않습니다. 그리고 다시 스크린을 누르고 나서 다른 앱을 사용하여 다시 돌아올 때 TextView와 정상적인 Android 이미지를 보여줍니다. 필요한 액티비티를 재구성합니다. 서비스에서 Activity 메소드를 호출 할 수 있습니까? 문제를 해결하는 방법은 무엇입니까?

Answer 1

배경 음악 서비스가 필요하며 메시지 또는 본드 활동이있는 서비스와 통신하여 서비스에서 활동 방법을 호출하지 않아 교차 프로세스 문제가 발생합니다.

실제로 배경 서비스와 음악 플레이어를 오픈 소스, 가사는 내가 쓴 한 비즈니스 프로젝트에서, 당신이 체크 아웃 : https://github.com/Wangchao0721/MusicPlayer

하지만 그것에 대한 추가 정보를 채우기 위해 시간이 없어, 단지 MediaPlayerActivity을 확인 .java를 액티비티 패키지에 넣으면, 이것을 어떻게 사용하는지 알게 될 것이다.