本人初学Android，最近做了一个实现安卓简单音乐播放功能的播放器，收获不少，于是便记录下来自己的思路与知识总结，重温自己的探索之路。

1  那么先上几张截图来看下程序实现效果吧

2 可以看出基本实现的功能有

暂停（播放），上（下）一首，停止播放

点击列表中歌曲进行播放，点击按钮以弹出歌曲列表

屏幕上显示歌曲名称，演唱者，专辑图片

显示播放进度条，拖拽进度条以控制播放

通知栏中显示相关信息，并可在通知栏上控制播放

3 总体开发思路

一共有两个Activity界面（分别是主界面和播放细节界面），一个用以在后台播放音乐的Service，一个可以和用户进行交互Notificatication。 为了能够使得活动与活动，活动与服务，活动与通知之间通信，采取发送广播的做法，由于我在MainActivity,PlayActivity,MusicService中都获取了歌曲信息列表，所以在他们之间直接传递歌曲下标location和状态isPlaying即可

核心是由MainActivity通过startService方法控制Service来进行播放

• MainActivity中点击事件发生后更新自己的UI，同时startService
• PlayActivity中点击事件发生后更新自己UI，发送广播给MainActivity，让MainActivity更新UI，startService，从而实现PlayActivity间接控制播放
• Notification点击事件发生后发生广播给MainActivity，让MainActivity更新UI，startService，从而实现Notification间接控制播放

4 重要功能实现

Cursor cursor=context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null)

for(int i=0;i<cursor.getCount();i++){
            cursor.moveToNext();
            Mp3Info mp3Info=new Mp3Info();
            mp3Info.setUrl(cursor.getString(cursor .getColumnIndex(MediaStore.Audio.Media.DATA)));
            mp3InfoList.add(mp3Info);

Intent intent=new Intent(MainActivity.this,PlayActivity.class);
                intent.putExtra("state",isPlaying);
                intent.putExtra("location",location);
                startActivity(intent);

//传递歌曲下标location并启动服务
        Intent intent=new Intent(MainActivity.this,MusicService.class);
        intent.putExtra("tag",0);
        intent.putExtra("location",location);
        startService(intent);

 //设置自动播放下一首
        mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            @Override
            public void onCompletion(MediaPlayer mediaPlayer) {
                if(mediaPlayer!=null){
                    try {
                        if (++location < mp3InfoList.size()) {
                            mediaPlayer.reset();
                            mediaPlayer.setDataSource(MusicService.this, Uri.parse(mp3InfoList.get(location).getUrl()));
                            mediaPlayer.prepare();
                            mediaPlayer.start();
                        }
                    }catch (Exception e){
                        e.printStackTrace();
                    }
                }

 public Integer doInBackground(Void...parms){

//设置while (true)以达到循环不断的目的 while (true){            try{                Thread.sleep(500);//线程沉睡500毫秒            }            catch (Exception e){                e.printStackTrace();            }            position=mediaPlayer.getCurrentPosition();//获得mediaPlayer当前播放进度            if(position<mediaPlayer.getDuration()){                Intent mIntent=new Intent("com.example.musicplayer.update_seekbar");                mIntent.putExtra("position",position);                sendBroadcast(mIntent);//发送广播            }else{                break;            }        }            return 0;        } 

//为SeekBar设置点击拖动事件
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                int progress=seekBar.getProgress();
                Intent intent=new Intent(MainActivity.this, MusicService.class);
                intent.putExtra("tag",2);
                intent.putExtra("progress",progress);
                startService(intent);
            }
        });

remoteViews = new RemoteViews(getPackageName(), R.layout.remoteviews_item_dl);//设置RemoteViews的布局
            remoteViews.setTextViewText(R.id.tv_filename, getPackageName());   // 设置标题
            remoteViews.setTextViewText(R.id.tv_content, "this is notification");   // 设置内容
            remoteViews.setImageViewBitmap(R.id.notification_imageView,bitmap);//设置控件Bitmap

          // 设置点击事件响应结果为发送广播            remoteViews.setOnClickPendingIntent(R.id.notification_next,PendingIntent.getBroadcast(this,0,            new Intent("com.example.musicplayer.notification.next").putExtra("tag2",2), PendingIntent.FLAG_UPDATE_CURRENT));            Notification notification=new NotificationCompat.builder(this).setContent(remotoViews).build();//构建出带有特定布局的通知              manager.notify(0,notification);//显示通知

    //通过AlertDialog显示歌曲列表
    public void showMusicList(){
        Log.d("PlayActivity","showMusicList start");
        LinearLayout linearLayoutMain = new LinearLayout(this);//自定义一个布局文件
        linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
        Log.d("PlayActivity","LinearLayout created");
        ListView listView = new ListView(this);//this为获取当前的上下文
        listView.setFadingEdgeLength(0);
        List<Map<String,String>>musicList=new ArrayList<Map<String, String>>();
        for(int i=0;i<mp3InfoList.size();i++){
            Map<String,String>item=new HashMap<String,String>();
            item.put("musicName",mp3InfoList.get(i).getTitle().toString());
            item.put("artist",mp3InfoList.get(i).getArtist().toString());
            musicList.add(item);
        }
        Log.d("PlayActivity","LinearLayout created and itialized");
         //
        SimpleAdapter adapter=new SimpleAdapter(PlayActivity.this,musicList,R.layout.music_item
                ,new String[]{"musicName","artist"}
                , new int[]{R.id.music_item_musicName,R.id.music_item_artist});
        Log.d("PlayActivity","SimpleAdapter created");
        listView.setAdapter(adapter);
        linearLayoutMain.addView(listView);
        Log.d("PlayActivity","listView was added to the linearLayout");
        final AlertDialog dialog=new AlertDialog.Builder(this).setTitle("歌曲列表").setView(linearLayoutMain)
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                        dialog.cancel();
                    }
                }).create();
        Log.d("PlayActivity","Dialog created");
        dialog.show();
        Log.d("PlayActivity","Dialog showed");
        //响应子项点击事件
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override

         //           注意这里的参数第三个参数Item在适配器中的位置            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {                //更新自身UI                musicNameView.setText(mp3InfoList.get(i).getTitle());                artistView.setText(mp3InfoList.get(i).getArtist());                durationView.setText(MediaUtil.formatTime(mp3InfoList.get(i).getDuration()));                //发送广播附带歌曲下标给MainActivity来控制服务播放歌曲                Intent intent=new Intent("com.example.musicplayer.react_to_playactiity");                intent.putExtra("tag1",4);                intent.putExtra("location",i);                sendBroadcast(intent);                Log.d("PlayActivity","broadcast sended");                dialog.cancel();                Log.d("PlayActivity","Dialog canceled");            }        });    }

5 开发思路的实现细节

1 首先新建保存mp3音乐相关属性信息的实体类Mp3Info（保存url，title，artist等等）

ublic class Mp3Info {
    private String url;//路径
    private String title;//歌曲名
    private String artist;//艺术家
    private long duration;//歌曲时长
    private long id;
    private long albumId;//以上两种Id用以获取专辑图片
    public Mp3Info(){

    }
    public Mp3Info(String url,String title,String artist,long duration,long id,long albumId){
        this.url=url;
        this.title=title;
        this.artist=artist;
        this.duration=duration;
        this.id=id;
        this.albumId=albumId;
    }
    public void setUrl(String url){
        this.url=url;
    }
    public void setTitle(String title){
        this.title=title;
    }
    public void setArtist(String artist){
        this.artist=artist;
    }
    public void setDuration(long duration){
        this.duration=duration;
    }
    public void setId(long id){this.id=id;}
    public void setAlbumId(long albumId){this.albumId=albumId;}
    public String getUrl(){
        return url;
    }
    public String getTitle(){
        return title;
    }
    public String getArtist(){
        return artist;
    }
    public long getDuration(){

        return duration;} public long getId() {        return id;    }    public long getAlbumId() {        return albumId;    }}

public class MediaUtil {    //获取专辑封面的Uri    private static final Uri albumArtUri = Uri.parse("content://media/external/audio/albumart");   //从安卓媒体库中获取歌曲信息并保存在程序的List中,并提供静态方法给其他类来直接获得生成的歌曲列表信息    public static List<Mp3Info>getMp3InfoList(Context context){        Cursor cursor=context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,               null);        List<Mp3Info>mp3InfoList=new ArrayList<>();        for(int i=0;i<cursor.getCount();i++){            cursor.moveToNext();            Mp3Info mp3Info=new Mp3Info();            mp3Info.setUrl(cursor.getString(cursor                    .getColumnIndex(MediaStore.Audio.Media.DATA)));            mp3Info.setTitle(cursor.getString(cursor                    .getColumnIndex(MediaStore.Audio.Media.TITLE)));            mp3Info.setArtist(cursor.getString(cursor                    .getColumnIndex(MediaStore.Audio.Media.ARTIST)));            mp3Info.setDuration(cursor.getLong(cursor                    .getColumnIndex(MediaStore.Audio.Media.DURATION)));            mp3Info.setId(cursor.getLong(cursor                    .getColumnIndex(MediaStore.Audio.Media._ID)));            mp3Info.setAlbumId(cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID)));             mp3InfoList.add(mp3Info);        }        return mp3InfoList;    }    /**     * 格式化时间，将毫秒转换为分:秒格式//将long类型转化为String型，     * @param time     * @return     */    public static String formatTime(long time) {        String min = time / (1000 * 60) + "";        String sec = time % (1000 * 60) + "";        if (min.length() < 2) {            min = "0" + time / (1000 * 60) + "";        } else {            min = time / (1000 * 60) + "";        }        if (sec.length() == 4) {            sec = "0" + (time % (1000 * 60)) + "";        } else if (sec.length() == 3) {            sec = "00" + (time % (1000 * 60)) + "";        } else if (sec.length() == 2) {            sec = "000" + (time % (1000 * 60)) + "";        } else if (sec.length() == 1) {            sec = "0000" + (time % (1000 * 60)) + "";        }        return min + ":" + sec.trim().substring(0, 2);    }    /**     * 获取默认专辑图片     * @param context     * @return     */    public static Bitmap getDefaultArtwork(Context context,boolean small) {        BitmapFactory.Options opts = new BitmapFactory.Options();        opts.inPreferredConfig = Bitmap.Config.RGB_565;        if(small){	//返回小图片            return BitmapFactory.decodeStream(context.getResources().openRawResource(R.drawable.music5), null, opts);        }        return BitmapFactory.decodeStream(context.getResources().openRawResource(R.drawable.defaultalbum), null, opts);    }    /**     * 从文件当中获取专辑封面位图     * @param context     * @param songid     * @param albumid     * @return     */    private static Bitmap getArtworkFromFile(Context context, long songid, long albumid){        Bitmap bm = null;        if(albumid < 0 && songid < 0) {            throw new IllegalArgumentException("Must specify an album or a song id");        }        try {            BitmapFactory.Options options = new BitmapFactory.Options();            FileDescriptor fd = null;            if(albumid < 0){                Uri uri = Uri.parse("content://media/external/audio/media/"                        + songid + "/albumart");                ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(uri, "r");                if(pfd != null) {                    fd = pfd.getFileDescriptor();                }            } else {                Uri uri = ContentUris.withAppendedId(albumArtUri, albumid);                ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(uri, "r");                if(pfd != null) {                    fd = pfd.getFileDescriptor();                }            }            options.inSampleSize = 1;            // 只进行大小判断            options.inJustDecodeBounds = true;            // 调用此方法得到options得到图片大小            BitmapFactory.decodeFileDescriptor(fd, null, options);            // 我们的目标是在800pixel的画面上显示            // 所以需要调用computeSampleSize得到图片缩放的比例            options.inSampleSize = 100;            // 我们得到了缩放的比例，现在开始正式读入Bitmap数据            options.inJustDecodeBounds = false;            options.inDither = false;            options.inPreferredConfig = Bitmap.Config.ARGB_8888;            //根据options参数，减少所需要的内存            bm = BitmapFactory.decodeFileDescriptor(fd, null, options);        } catch (FileNotFoundException e) {            e.printStackTrace();        }        return bm;    }    /**     * 获取专辑封面位图对象     * @param context     * @param song_id     * @param album_id     * @param allowdefalut     * @return     */    public static Bitmap getArtwork(Context context, long song_id, long album_id, boolean allowdefalut, boolean small){        if(album_id < 0) {            if(song_id < 0) {                Bitmap bm = getArtworkFromFile(context, song_id, -1);                if(bm != null) {                    return bm;                }            }            if(allowdefalut) {                return getDefaultArtwork(context, small);            }            return null;        }        ContentResolver res = context.getContentResolver();        Uri uri = ContentUris.withAppendedId(albumArtUri, album_id);        if(uri != null) {            InputStream in = null;            try {                in = res.openInputStream(uri);                BitmapFactory.Options options = new BitmapFactory.Options();                //先制定原始大小                options.inSampleSize = 1;                //只进行大小判断                options.inJustDecodeBounds = true;                //调用此方法得到options得到图片的大小                BitmapFactory.decodeStream(in, null, options);                /** 我们的目标是在你N pixel的画面上显示。 所以需要调用computeSampleSize得到图片缩放的比例 **/                /** 这里的target为800是根据默认专辑图片大小决定的，800只是测试数字但是试验后发现完美的结合 **/                if(small){                    options.inSampleSize = computeSampleSize(options, 40);                } else{                    options.inSampleSize = computeSampleSize(options, 600);                }                // 我们得到了缩放比例，现在开始正式读入Bitmap数据                options.inJustDecodeBounds = false;                options.inDither = false;                options.inPreferredConfig = Bitmap.Config.ARGB_8888;                in = res.openInputStream(uri);                return BitmapFactory.decodeStream(in, null, options);            } catch (FileNotFoundException e) {                Bitmap bm = getArtworkFromFile(context, song_id, album_id);                if(bm != null) {                    if(bm.getConfig() == null) {                        bm = bm.copy(Bitmap.Config.RGB_565, false);                        if(bm == null && allowdefalut) {                            return getDefaultArtwork(context, small);                        }                    }                } else if(allowdefalut) {                    bm = getDefaultArtwork(context, small);                }                return bm;            } finally {                try {                    if(in != null) {                        in.close();                    }                } catch (IOException e) {                    e.printStackTrace();                }            }        }        return null;    }    /**     * 对图片进行合适的缩放     * @param options     * @param target     * @return     */    public static int computeSampleSize(BitmapFactory.Options options, int target) {        int w = options.outWidth;        int h = options.outHeight;        int candidateW = w / target;        int candidateH = h / target;        int candidate = Math.max(candidateW, candidateH);        if(candidate == 0) {            return 1;        }        if(candidate > 1) {            if((w > target) && (w / candidate) < target) {                candidate -= 1;            }        }        if(candidate > 1) {            if((h > target) && (h / candidate) < target) {                candidate -= 1;            }        }        return candidate;    }}

主界面：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mainActivity_drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <android.support.v7.widget.Toolbar
        android:id="@+id/mainActivity_toolBar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"/>
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/mainActivity_toolBar"
    android:background="#FFF">
    <ListView
        android:id="@+id/musicName_list"
        android:layout_width="match_parent"
        android:layout_height="440dp"
        android:textColor="#FFF"/>
     <RelativeLayout
         android:id="@+id/mainActivity_seekBarLayout"
         android:layout_width="match_parent"
         android:layout_height="35dp"
         android:layout_below="@+id/musicName_list"
         android:layout_alignParentLeft="true"
         android:layout_alignParentStart="true"
         android:background="@drawable/drawable_bg">
         <SeekBar
             android:id="@+id/mainActivity_seekBar"
             android:layout_width="match_parent"
             android:layout_height="20dp"
             android:thumb="@drawable/media_player_progress_button"
             />

         <TextView
             android:id="@+id/main_current_position"
             android:layout_width="wrap_content"
             android:layout_height="25dp"
             android:layout_below="@id/mainActivity_seekBar"
             android:text="0:00"
             android:textColor="#060606"/>

         <TextView
             android:id="@+id/main_final_position"
             android:layout_width="wrap_content"
             android:layout_height="25dp"
             android:layout_alignParentRight="true"
             android:layout_below="@id/mainActivity_seekBar"
             android:text="3:00"
             android:textColor="#090808"/>

     </RelativeLayout>
   <RelativeLayout
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       android:layout_alignParentBottom="true"
       android:background="#7e7677"
       android:layout_below="@+id/mainActivity_seekBarLayout">
       <ImageView
           android:id="@+id/album_view"
           android:layout_width="80dp"
           android:layout_height="match_parent"
           />
       <TextView
           android:id="@+id/mainActivity_musicName"
           android:layout_width="80dp"
           android:layout_toRightOf="@+id/album_view"
           android:layout_marginLeft="5dp"
           android:layout_height="wrap_content"
           android:text="歌曲名称"
           android:textColor="#090909"/>
       <TextView
           android:id="@+id/mainActivity_artist"
           android:layout_width="80dp"
           android:layout_height="wrap_content"
           android:layout_below="@+id/mainActivity_musicName"
           android:layout_marginLeft="5dp"
           android:layout_toRightOf="@+id/album_view"
           android:text="歌曲作者"
           android:textColor="#060606"/>
       <ImageButton
           android:id="@+id/mainActivity_play_pause"
           android:layout_width="50dp"
           android:layout_height="60dp"
           android:layout_centerInParent="true"
           android:layout_toLeftOf="@+id/mainActivity_next"
           app:srcCompat="@drawable/play"/>
       <ImageButton
           android:id="@+id/mainActivity_next"
           android:layout_width="50dp"
           android:layout_height="60dp"
           android:layout_centerInParent="true"
          app:srcCompat="@drawable/next"
           android:layout_toLeftOf="@+id/mainActivity_menu"/>
       <ImageButton
           android:id="@+id/mainActivity_menu"
           android:layout_width="50dp"
           android:layout_height="60dp"
           android:layout_centerInParent="true"
           android:layout_alignParentRight="true"
           app:srcCompat="@drawable/menu"
           />
   </RelativeLayout>


</RelativeLayout>
</RelativeLayout>
    <android.support.design.widget.NavigationView
        android:id="@+id/mainActivity_nav_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/nav_menu"
        app:headerLayout="@layout/nav_header"
        >
    </android.support.design.widget.NavigationView>

</android.support.v4.widget.DrawerLayout>

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="#885959"    >    <RelativeLayout        android:id="@+id/play_activity_toolBar1"        android:layout_width="match_parent"        android:layout_height="40dp"        android:layout_alignParentTop="true"        android:layout_alignParentLeft="true"        >            android:layout_width="match_parent"            android:layout_height="match_parent">            <Button                android:id="@+id/playActivity_return"                android:layout_width="45dp"                android:layout_height="30dp"                android:background="@drawable/back_return_normal"/>            <TextView                android:id="@+id/playActivity_musicName"                android:layout_width="match_parent"                android:layout_height="20dp"                android:layout_toRightOf="@+id/playActivity_return"                android:text="歌曲名称"                android:layout_marginLeft="5dp"                android:textColor="#fcfcfc"/>            <TextView                android:id="@+id/playActivity_artist"                android:layout_width="match_parent"                android:layout_marginLeft="5dp"                android:layout_height="20dp"                android:layout_toRightOf="@+id/playActivity_return"                android:layout_below="@+id/playActivity_musicName"                android:text="演唱者"                android:textColor="#c3b9b9"                />    </RelativeLayout>    <ScrollView        android:id="@+id/playActivity_musicLyrics"        android:layout_width="match_parent"        android:layout_height="400dp"        android:layout_alignParentTop="true"        android:layout_alignParentLeft="true"        android:layout_alignParentStart="true"        android:layout_above="@+id/playActivity_seekbarLayout">    </ScrollView>    <RelativeLayout        android:id="@+id/playActivity_seekbarLayout"        android:layout_width="match_parent"        android:layout_height="35dp"        android:background="@drawable/drawable_bg"        android:layout_above="@+id/playActivity_toolBar2">        <SeekBar            android:id="@+id/playActivity_seekBar"            android:layout_width="match_parent"            android:layout_height="20dp"            android:thumb="@drawable/media_player_progress_button"            />        <TextView            android:id="@+id/current_position"            android:layout_width="wrap_content"            android:layout_height="25dp"            android:layout_below="@id/playActivity_seekBar"            android:text="0:00"            android:textColor="#FFF"/>        <TextView            android:id="@+id/final_position"            android:layout_width="wrap_content"            android:layout_height="25dp"            android:layout_alignParentRight="true"            android:layout_below="@id/playActivity_seekBar"            android:text="3:00"            android:textColor="#FFF"/>    </RelativeLayout>    <RelativeLayout        android:id="@+id/playActivity_toolBar2"        android:layout_width="match_parent"        android:layout_height="70dp"        android:layout_alignParentBottom="true"        android:layout_alignParentLeft="true"        android:layout_alignParentStart="true">        <ImageButton            android:id="@+id/stop"            android:layout_width="50dp"            android:layout_margin="10dp"            android:layout_height="match_parent"            app:srcCompat="@drawable/stop"/>        <ImageButton            android:id="@+id/previous"            android:layout_width="50dp"            android:layout_margin="10dp"            android:layout_height="match_parent"            android:layout_toRightOf="@+id/stop"            app:srcCompat="@drawable/previous"/>        <ImageButton            android:id="@+id/play_pause"            android:layout_margin="10dp"            android:layout_width="50dp"            android:layout_height="match_parent"            android:layout_toRightOf="@+id/previous"            app:srcCompat="@drawable/play"             />        <ImageButton            android:id="@+id/next_music"            android:layout_width="50dp"            android:layout_margin="10dp"            android:layout_height="match_parent"            android:layout_toRightOf="@+id/play_pause"            app:srcCompat="@drawable/next"            />        <ImageButton            android:id="@+id/music_menu"            android:layout_width="50dp"            android:layout_margin="10dp"            android:layout_height="match_parent"            android:layout_toRightOf="@+id/next_music"            app:srcCompat="@drawable/playqueue"            />    </RelativeLayout></RelativeLayout>

public class MainActivity extends AppCompatActivity {    static ListView listView;    List<Mp3Info>mp3InfoList;    Mp3Info mp3Info;    static int location=0;    static Boolean isPlaying=false;    List musicNameList=new ArrayList<>();    static TextView musicNameView;    static TextView artistView;    static ImageView albumView;    static ImageButton playOrPauseButton;    static ImageButton nextButton;    static SeekBar seekBar;    static TextView currentTiemView;    static TextView durationView;    DrawerLayout drawerLayout;    String Tag="MainActivity";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);          //ToolBar及DrawerLayout        Toolbar toolbar=(Toolbar)findViewById(R.id.mainActivity_toolBar);        setSupportActionBar(toolbar);        ActionBar actionBar=getSupportActionBar();        if(actionBar!=null){            actionBar.setDisplayHomeAsUpEnabled(true);            actionBar.setHomeAsUpIndicator(R.drawable.menu);        }        drawerLayout=(DrawerLayout)findViewById(R.id.mainActivity_drawer_layout);          //获得各个控件并设置点击事件        musicNameView=(TextView)findViewById(R.id.mainActivity_musicName);        artistView=(TextView)findViewById(R.id.mainActivity_artist);        playOrPauseButton=(ImageButton)findViewById(R.id.mainActivity_play_pause);        nextButton=(ImageButton)findViewById(R.id.mainActivity_next);        seekBar=(SeekBar)findViewById(R.id.mainActivity_seekBar);        currentTiemView=(TextView)findViewById(R.id.main_current_position) ;        durationView=(TextView)findViewById(R.id.main_final_position);        albumView=(ImageView)findViewById(R.id.album_view);          //设置各控件初始视图为上次离开时所播放的歌曲，如果进程已被Kill掉，则为第一首        mp3InfoList=MediaUtil.getMp3InfoList(MainActivity.this);        mp3Info=mp3InfoList.get(location);        musicNameView.setText(mp3Info.getTitle());        artistView.setText(mp3Info.getArtist());        long id=mp3Info.getId();        long albumId=mp3Info.getAlbumId();        albumView.setImageBitmap(MediaUtil.getArtwork(this, id,                albumId, true, false));        if(isPlaying)            playOrPauseButton.setImageResource(R.drawable.pause);        else playOrPauseButton.setImageResource(R.drawable.play);           //专辑图片点击事件，进入PlayActivity中，并通过Intent传递location和isPlaying状态        albumView.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Intent intent=new Intent(MainActivity.this,PlayActivity.class);                intent.putExtra("state",isPlaying);                intent.putExtra("location",location);                startActivity(intent);            }        });         //暂停、播放按钮点击事件        playOrPauseButton.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                playOrpause();            }        });         //下一首点击事件        nextButton.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                nextMusic();            }        });        //从媒体库中获得音乐列表并显示到ListView中,同时设置点击事件        listView=(ListView)findViewById(R.id.musicName_list) ;        for(int i=0;i<mp3InfoList.size();i++)            musicNameList.add(mp3InfoList.get(i).getTitle());        ArrayAdapter aa=new ArrayAdapter(this,android.R.layout.simple_list_item_1,musicNameList);        listView.setAdapter(aa);        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {           @Override           public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {               location=i;               setPlay(location);           }        });         //注册监听SeekBar变化的监听器        IntentFilter filter=new IntentFilter();        filter.addAction("com.example.musicplayer.update_seekbar");        UpdateSeekbarBroadcast receiver=new UpdateSeekbarBroadcast();        registerReceiver(receiver,filter);         //监听PlayActivity的点击事件        IntentFilter filter1=new IntentFilter();        filter1.addAction("com.example.musicplayer.react_to_playactiity");        PlayActivityBroadcast receiver1=new PlayActivityBroadcast();        registerReceiver(receiver1,filter1);         //注册监听Notification的监听器        IntentFilter filter2=new IntentFilter();        filter2.addAction("com.example.musicplayer.notification.previous");        filter2.addAction("com.example.musicplayer.notification.play_pause");        filter2.addAction("com.example.musicplayer.notification.next");        NotificationBroadcast receiver2=new NotificationBroadcast();        registerReceiver(receiver2,filter2);         //注册监听后台顺序播放的监听器        IntentFilter filter3=new IntentFilter();        filter3.addAction("com.example.musicplayer.order_play");        OrderPlayBroadcast receiver3=new OrderPlayBroadcast();        registerReceiver(receiver3,filter3);         //为SeekBar设置点击拖动事件        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {            @Override            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {            }            @Override            public void onStartTrackingTouch(SeekBar seekBar) {            }            @Override            public void onStopTrackingTouch(SeekBar seekBar) {                int progress=seekBar.getProgress();                Intent intent=new Intent(MainActivity.this, MusicService.class);                intent.putExtra("tag",2);                intent.putExtra("progress",progress);                startService(intent);            }        });    }    public boolean onCreateOptionsMenu(Menu menu){        getMenuInflater().inflate(R.menu.toolbar,menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem menuItem){        switch (menuItem.getItemId()){            case android.R.id.home:drawerLayout.openDrawer(GravityCompat.START);                break;            case R.id.search:                Toast.makeText(MainActivity.this,"You clicked the search button",Toast.LENGTH_SHORT).show();                break;        }        return true;    }    //设置播放某一首歌曲    public void setPlay(int location){        //切换播放状态        isPlaying=true;        //根据要播放的音乐曲目更新MainActivity的UI        mp3Info=mp3InfoList.get(location);        long id=mp3Info.getId();        long albumId=mp3Info.getAlbumId();        musicNameView.setText(mp3Info.getTitle());        artistView.setText(mp3Info.getArtist());        Bitmap bitmap = MediaUtil.getArtwork(this, id,                albumId, true, false);// 获取专辑位图对象，为大图        albumView.setImageBitmap(bitmap);        //切换播放状态图标            playOrPauseButton.setImageResource(R.drawable.pause);        seekBar.setMax((int)mp3Info.getDuration());        currentTiemView.setText("0:00");        durationView.setText(MediaUtil.formatTime(mp3Info.getDuration()));        //传递歌曲下标location并启动服务        Intent intent=new Intent(MainActivity.this,MusicService.class);        intent.putExtra("tag",0);        intent.putExtra("location",location);        startService(intent);    }    //播放下一首歌曲    public void nextMusic(){        if((++location)<mp3InfoList.size()){            setPlay(location);        }    }    //播放上一首歌曲    public void previousMusic(){        if ((--location)>=0){            setPlay(location);        }    }    //暂停或继续播放    public void playOrpause(){        Intent intent=new Intent(MainActivity.this,MusicService.class);        //切换播放状态并改变状态图标        isPlaying=!isPlaying;        if(isPlaying)            playOrPauseButton.setImageResource(R.drawable.pause);        else playOrPauseButton.setImageResource(R.drawable.play);        intent.putExtra("tag",1);        intent.putExtra("state",isPlaying);        startService(intent);    }    //停止播放此首音乐，并将进度条滑至开始处    public void stopMusic(){        Intent intent=new Intent(MainActivity.this,MusicService.class);        intent.putExtra("tag",3);        if(isPlaying)            playOrPauseButton.setImageResource(R.drawable.play);        else playOrPauseButton.setImageResource(R.drawable.pause);        startService(intent);    }    //监听来自Service的SeekBar变化    class UpdateSeekbarBroadcast extends BroadcastReceiver{        @Override        public void onReceive(Context context,Intent intent){            int position=intent.getIntExtra("position",0);            currentTiemView.setText(MediaUtil.formatTime(position));            seekBar.setProgress(position);        }    }    //接收来自PlayActivity的广播    class PlayActivityBroadcast extends BroadcastReceiver{        @Override        public void onReceive(Context context,Intent intent){            int tag1=intent.getIntExtra("tag1",-1);            switch (tag1){                case 0: {                    playOrpause();                }                    break;                case 1:previousMusic();                    break;                case 2:nextMusic();                    break;                case 3:stopMusic();                    default:                        break;                case 4:{                    location=intent.getIntExtra("location",5);                    setPlay(location);                }            }        }    }    //接收来自Notification的广播    class NotificationBroadcast extends BroadcastReceiver{        @Override        public void onReceive(Context context,Intent intent){            int tag2=intent.getIntExtra("tag2",-1);            LogUtil.d(Tag,"received the broadcast from notification");            switch (tag2){                case 0:previousMusic();                    break;                case 1:{                    playOrpause();                    isPlaying=intent.getBooleanExtra("state",false);                }                    break;                case 2:nextMusic();                    break;                default:                    break;            }        }    }    //接收来自后台自动播放的广播以更新UI    class OrderPlayBroadcast extends BroadcastReceiver{        @Override        public void onReceive(Context context,Intent intent){            LogUtil.d(Tag,"update ui according to the orderly play");            location=intent.getIntExtra("location",-1);            mp3Info=mp3InfoList.get(location);            long id=mp3Info.getId();            long albumId=mp3Info.getAlbumId();            musicNameView.setText(mp3Info.getTitle());            artistView.setText(mp3Info.getArtist());            Bitmap bitmap = MediaUtil.getArtwork(MainActivity.this, id,                    albumId, true, false);// 获取专辑位图对象，为大图            albumView.setImageBitmap(bitmap);            seekBar.setMax((int)mp3Info.getDuration());            currentTiemView.setText("0:00");            durationView.setText(MediaUtil.formatTime(mp3Info.getDuration()));        }    }}

public class PlayActivity extends AppCompatActivity implements View.OnClickListener {
    TextView musicNameView,artistView;
    Button returnBack;
    ImageButton stop,previousMusic,playOrPauseButton,nextMusic,musicList;
    SeekBar seekBar;
    TextView currentTimeView,durationView;
    Intent intent;
    static int location=0;
    static Boolean isPlaying=false;
    Mp3Info mp3Info;
    List<Mp3Info>mp3InfoList=new ArrayList<>();
    String[]musicNameList;
    String Tag="PlayActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_play);
        //获得歌曲列表信息
        mp3InfoList=MediaUtil.getMp3InfoList(PlayActivity.this);
        //获得各控件实例
        musicNameView=(TextView)findViewById(R.id.playActivity_musicName) ;
        artistView=(TextView)findViewById(R.id.playActivity_artist);
        stop=(ImageButton)findViewById(R.id.stop);
        previousMusic=(ImageButton)findViewById(R.id.previous);
        playOrPauseButton=(ImageButton)findViewById(R.id.play_pause);
        nextMusic=(ImageButton)findViewById(R.id.next_music);
        musicList=(ImageButton)findViewById(R.id.music_menu);
        returnBack=(Button)findViewById(R.id.playActivity_return);
        seekBar=(SeekBar)findViewById(R.id.playActivity_seekBar);
        currentTimeView=(TextView)findViewById(R.id.current_position);
        durationView=(TextView)findViewById(R.id.final_position);
        //从MainActivity中传递过来的数据
        Intent intent1=getIntent();
        location=intent1.getIntExtra("location",0);
        isPlaying=intent1.getBooleanExtra("state",false);
        //根据传递过来的数据更新UI视图
        seekBar.setMax((int)(mp3InfoList.get(location).getDuration()));
        currentTimeView.setText("0:00");
        durationView.setText(MediaUtil.formatTime(mp3InfoList.get(location).getDuration()));
        musicNameView.setText(mp3InfoList.get(location).getTitle());
        artistView.setText(mp3InfoList.get(location).getArtist());
        durationView.setText(MediaUtil.formatTime(mp3InfoList.get(location).getDuration()));
        if(isPlaying)
            playOrPauseButton.setImageResource(R.drawable.pause);
        else playOrPauseButton.setImageResource(R.drawable.play);
        //注册seekBar监听器
        IntentFilter filter=new IntentFilter();
        filter.addAction("com.example.musicplayer.update_seekbar");
        UpdateSeekbarBroadcast receiver=new UpdateSeekbarBroadcast();
        registerReceiver(receiver,filter);
        //注册后台顺序播放的监听器
        IntentFilter filter1=new IntentFilter();
        filter1.addAction("com.example.musicplayer.order_play");
        OrderPlayBroadcast receiver1=new OrderPlayBroadcast();
        registerReceiver(receiver1,filter1);
        //为SeekBar设置点击拖动事件
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            }
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                int progress=seekBar.getProgress();
                Intent intent=new Intent(PlayActivity.this, MusicService.class);
                intent.putExtra("tag",2);
                intent.putExtra("progress",progress);
                startService(intent);
            }
        });
        //设置各按钮点击事件
        stop.setOnClickListener(this);
        previousMusic.setOnClickListener(this);
        playOrPauseButton.setOnClickListener(this);
        nextMusic.setOnClickListener(this);
        musicList.setOnClickListener(this);
    }
    //监听来自Service的SeekBar变化
    class UpdateSeekbarBroadcast extends BroadcastReceiver{
        @Override
        public void onReceive(Context context,Intent intent){
            int position=intent.getIntExtra("position",0);
            currentTimeView.setText(MediaUtil.formatTime(position));
            seekBar.setProgress(position);

        }
    }
    //接收来自后台自动播放的广播以更新UI
    class OrderPlayBroadcast extends BroadcastReceiver{
        @Override
        public void onReceive(Context context,Intent intent){
            LogUtil.d(Tag,"PlayActivity receive broadcast from service orderly play to update UI ");
            location=intent.getIntExtra("location",-1);
            mp3Info=mp3InfoList.get(location);
            musicNameView.setText(mp3Info.getTitle());
            artistView.setText(mp3Info.getArtist());
            seekBar.setMax((int)mp3Info.getDuration());
            currentTimeView.setText("0:00");
            durationView.setText(MediaUtil.formatTime(mp3Info.getDuration()));
        }
    }
    @Override
    public void onClick(View view){
        Intent intent=new Intent("com.example.musicplayer.react_to_playactiity");
        switch (view.getId()){
            case R.id.stop :{
                intent.putExtra("tag1",3);
            }
                break;
            case R.id.previous: {
                isPlaying=!isPlaying;
                previousMusic();
                intent.putExtra("tag1", 1);
            }
                break;
            case R.id.play_pause:{
                isPlaying=!isPlaying;
                if(isPlaying) {
                    playOrPauseButton.setImageResource(R.drawable.pause);
                }
                else {
                    playOrPauseButton.setImageResource(R.drawable.play);
                }
                intent.putExtra("tag1",0);
                intent.putExtra("state",isPlaying);

            }
                break;
            case R.id.next_music:{
                nextMusic();
                intent.putExtra("tag1",2);
            }
                break;
            case R.id.music_menu:
                Log.d("PlayActivity","press the button music_menu");
                 showMusicList();
                break;
            default:
                break;

        }
        sendBroadcast(intent);
    }
    //根据点击事件更新UI视图
    public void previousMusic(){
        if((--location)>=0)
        {
            seekBar.setMax((int)(mp3InfoList.get(location).getDuration()));
            currentTimeView.setText("0:00");
            durationView.setText(MediaUtil.formatTime(mp3InfoList.get(location).getDuration()));
            musicNameView.setText(mp3InfoList.get(location).getTitle());
            artistView.setText(mp3InfoList.get(location).getArtist());
            playOrPauseButton.setImageResource(R.drawable.pause);
        }
    }
    public void nextMusic(){
        if((++location)>=0)
        {
            seekBar.setMax((int)(mp3InfoList.get(location).getDuration()));
            currentTimeView.setText("0:00");
            durationView.setText(MediaUtil.formatTime(mp3InfoList.get(location).getDuration()));
            musicNameView.setText(mp3InfoList.get(location).getTitle());
            artistView.setText(mp3InfoList.get(location).getArtist());
            playOrPauseButton.setImageResource(R.drawable.pause);
        }
    }
    //通过AlertDialog显示歌曲列表
    public void showMusicList(){
        Log.d("PlayActivity","showMusicList start");
        LinearLayout linearLayoutMain = new LinearLayout(this);//自定义一个布局文件
        linearLayoutMain.setLayoutParams(new LinearLayoutCompat.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
        Log.d("PlayActivity","LinearLayout created");
        ListView listView = new ListView(this);//this为获取当前的上下文
        listView.setFadingEdgeLength(0);
        List<Map<String,String>>musicList=new ArrayList<Map<String, String>>();
        for(int i=0;i<mp3InfoList.size();i++){
            Map<String,String>item=new HashMap<String,String>();
            item.put("musicName",mp3InfoList.get(i).getTitle().toString());
            item.put("artist",mp3InfoList.get(i).getArtist().toString());
            musicList.add(item);
        }
        Log.d("PlayActivity","LinearLayout created and itialized");

        SimpleAdapter adapter=new SimpleAdapter(PlayActivity.this,musicList,R.layout.music_item
                ,new String[]{"musicName","artist"}
                , new int[]{R.id.music_item_musicName,R.id.music_item_artist});
        Log.d("PlayActivity","SimpleAdapter created");
        listView.setAdapter(adapter);
        linearLayoutMain.addView(listView);
        Log.d("PlayActivity","listView was added to the linearLayout");
        final AlertDialog dialog=new AlertDialog.Builder(this).setTitle("歌曲列表").setView(linearLayoutMain)
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub
                        dialog.cancel();
                    }
                }).create();
        Log.d("PlayActivity","Dialog created");
        dialog.show();
        Log.d("PlayActivity","Dialog showed");
        //响应子项点击事件
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                //更新自身UI
                musicNameView.setText(mp3InfoList.get(i).getTitle());
                artistView.setText(mp3InfoList.get(i).getArtist());
                durationView.setText(MediaUtil.formatTime(mp3InfoList.get(i).getDuration()));
                //发送广播附带歌曲下标给MainActivity来控制服务播放歌曲
                Intent intent=new Intent("com.example.musicplayer.react_to_playactiity");
                intent.putExtra("tag1",4);
                intent.putExtra("location",i);
                sendBroadcast(intent);
                Log.d("PlayActivity","broadcast sended");
                dialog.cancel();
                Log.d("PlayActivity","Dialog canceled");
            }
        });
    }

}

public class MusicService extends Service {
    List<Mp3Info> mp3InfoList = new ArrayList<>();
    MediaPlayer mediaPlayer;
    Mp3Info mp3Info;
    Notification notification;
    static int location;
    int position;
    static Boolean isPlaying=false;
    RemoteViews contecntViews;
    public MusicService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        mediaPlayer=new MediaPlayer();
        //获得歌曲Mp3Info类列表
        mp3InfoList = MediaUtil.getMp3InfoList(MusicService.this);

    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        Log.d("MusicService", "service onStartommand");
        int tag= intent.getIntExtra("tag", -1);
        switch (tag) {
            case 0: {
                isPlaying=true;
                location=intent.getIntExtra("location",-1);
                mp3Info=mp3InfoList.get(location);
                String url = mp3Info.getUrl();
                String title=mp3Info.getTitle();
                String artist=mp3Info.getArtist();
                long id=mp3Info.getId();
                long albumId=mp3Info.getAlbumId();
                try {
                    if (mediaPlayer != null) {
                        mediaPlayer.reset();
                    }
                    mediaPlayer.setDataSource(this, Uri.parse(url));
                    mediaPlayer.prepare();
                    mediaPlayer.start();
                    showNotification(title,artist,id,albumId);

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }break;
            case 1:{
                    if(mediaPlayer!=null) {
                        if (mediaPlayer.isPlaying()) {
                            mediaPlayer.pause();
                        } else mediaPlayer.start();
                    }
                    isPlaying=intent.getBooleanExtra("state",false);
                if(isPlaying==true)
                   isPlaying=false;
                else
                   isPlaying=true;

            }break;
            case 2:{
                isPlaying=true;
                int progress=intent.getIntExtra("progress",0);
                if(mediaPlayer!=null){
                    mediaPlayer.seekTo(progress);
                }
            }break;
            case 3:{
                mediaPlayer.stop();
                try{
                    mediaPlayer.prepare();
                    mediaPlayer.seekTo(0);}
                catch (Exception e){
                    e.printStackTrace();
                }
            } break;
        }
        //
         new PlayProgress().execute();
        //设置自动播放下一首
        mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            @Override
            public void onCompletion(MediaPlayer mediaPlayer) {
                if(mediaPlayer!=null){
                    try {
                        if (++location < mp3InfoList.size()) {
                            mediaPlayer.reset();
                            mediaPlayer.setDataSource(MusicService.this, Uri.parse(mp3InfoList.get(location).getUrl()));
                            mediaPlayer.prepare();
                            mediaPlayer.start();
                        }
                    }catch (Exception e){
                        e.printStackTrace();
                    }
                }
                //通过发送广播让MainActivity,PlayActivity更新UI
                Intent intent=new Intent("com.example.musicplayer.order_play");
                intent.putExtra("location",location);
                sendBroadcast(intent);
                //后台更新NotificationUI
                isPlaying=true;
                mp3Info=mp3InfoList.get(location);
                String title=mp3Info.getTitle();
                String artist=mp3Info.getArtist();
                long id=mp3Info.getId();
                long albumId=mp3Info.getAlbumId();
                showNotification(title,artist,id,albumId);
            }
        });
        return super.onStartCommand(intent, flags, startId);
    }
    public class PlayProgress extends AsyncTask<Void,Integer,Integer>{
        @Override
        public void onPreExecute(){
            super.onPreExecute();
        }
        @Override
        public Integer doInBackground(Void...parms){
            while (true){
            try{
                Thread.sleep(500);
            }
            catch (Exception e){
                e.printStackTrace();
            }
            position=mediaPlayer.getCurrentPosition();
            if(position<mediaPlayer.getDuration()){
                Intent mIntent=new Intent("com.example.musicplayer.update_seekbar");
                mIntent.putExtra("position",position);
                sendBroadcast(mIntent);
            }else{
                break;
            }
        }
            return 0;
        }
        @Override
        protected void onPostExecute(Integer integer) {
            Log.d("===","异步类执行完毕");
            super.onPostExecute(integer);
        }
    }
    //通知栏
    public void showNotification(String title, String artist, long id, long albumId){
        NotificationManager manager=(NotificationManager)getSystemService(NOTIFICATION_SERVICE);
        NotificationCompat.Builder builder= new NotificationCompat.Builder(this);
        contecntViews =new RemoteViews(getPackageName(),R.layout.notification_music);
        contecntViews.setTextViewText(R.id.notification_musicName,title);
        contecntViews.setTextViewText(R.id.notification_artist,artist);
        Bitmap bitmap = MediaUtil.getArtwork(this, id,
                albumId, true, false);// 获取专辑位图对象，为大图
        contecntViews.setImageViewBitmap(R.id.notification_imageView,bitmap);
        contecntViews.setOnClickPendingIntent(R.id.notification_previousMusic,PendingIntent.getBroadcast(this,0,
                new Intent("com.example.musicplayer.notification.previous").putExtra("tag2",0), PendingIntent.FLAG_UPDATE_CURRENT));
        contecntViews.setOnClickPendingIntent(R.id.notification_play_pause,PendingIntent.getBroadcast(this,0,
                new Intent("com.example.musicplayer.notification.play_pause").putExtra("tag2",1).putExtra("state",!isPlaying), PendingIntent.FLAG_UPDATE_CURRENT));
        contecntViews.setOnClickPendingIntent(R.id.notification_next,PendingIntent.getBroadcast(this,0,
                new Intent("com.example.musicplayer.notification.next").putExtra("tag2",2), PendingIntent.FLAG_UPDATE_CURRENT));
        notification=builder.setContent(contecntViews).setSmallIcon(R.mipmap.ic_launcher).build();
        manager.notify(0,notification);

    }
    @Override
    public void onDestroy(){
        super.onDestroy();
        mediaPlayer.stop();
        mediaPlayer.release();

    }
}