Using ContentResolver to report errors in service

problem description

using ContentResolver to report an error in service, the error is as follows, how to solve it?

error

FATAL EXCEPTION: main
Process: com.mp.mmedicaplayer, PID: 16990
  java.lang.RuntimeException: Unable to instantiate service com.mp.mmedicaplayer.service.MusicService: java.lang.NullPointerException: Attempt to invoke virtual method "android.content.ContentResolver android.content.Context.getContentResolver()" on a null object reference
  at android.app.ActivityThread.handleCreateService(ActivityThread.java:3390)
  at android.app.ActivityThread.-wrap5(ActivityThread.java)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1753)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:159)
  at android.app.ActivityThread.main(ActivityThread.java:6385)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1096)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:883)
   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method "android.content.ContentResolver android.content.Context.getContentResolver()" on a null object reference
  at com.mp.mmedicaplayer.service.MusicService.getMusicToArray(MusicService.java:211)
  at com.mp.mmedicaplayer.service.MusicService.<init>(MusicService.java:48)
  at java.lang.Class.newInstance(Native Method)
  at android.app.ActivityThread.handleCreateService(ActivityThread.java:3387)
  at android.app.ActivityThread.-wrap5(ActivityThread.java)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1753)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:159)
  at android.app.ActivityThread.main(ActivityThread.java:6385)
  at java.lang.reflect.Method.invoke(Native Method)

Code

public void getMusicToArray(){
        /**
         * 
         *
         */
        ContentResolver contentResolver = getContentResolver();
        Cursor cursor = contentResolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null,null,MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
        List<MusicListData> mListData = new ArrayList<>();
        //Cursor
        if(cursor.moveToFirst()){
            for(int i = 0; i <cursor.getCount();iPP) {
                MusicListData data = new MusicListData();
                long id = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media._ID));
                String title = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
                String artist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));
                long duration = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.DURATION));
                long size = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.SIZE));
                String url = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
                String abum = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));
                long albulm_id = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));
                int ismusic = cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.IS_MUSIC));
                Log.d("MMMM",url);

                if (ismusic != 0 && duration / (500 * 60) >= 1) {
                    Log.d("M","2");

                    musicPath[i] = url;

                    data.setTitle(title);
                    data.setUrl(url);
                    data.setSonger(artist);
                    mListData.add(data);
                }
                //
                cursor.moveToNext();
            }

        }
        //
        cursor.close();
    }

public abstract class Service extends ContextWrapper implements ComponentCallbacks2 { ... ... } public class ContextWrapper extends Context { Context mBase; protected void attachBaseContext(Context base) { if (mBase != null) { throw new IllegalStateException("Base context already set"); } mBase = base; } @Override public ContentResolver getContentResolver() { return mBase.getContentResolver(); } }