Android MusicPlayer

        最近一直在看android媒體播放的MediaPlayer類，本來以爲用MediaPlayer的幾個方法就可以完成基本音樂播放的功能了，然並卵，其中有好多需要自己去思考完善的，待我一一道來。

        一.在手機的SOLitaDatebase中獲取音頻文件

        要實現手機音樂播放的功能，首先要掃描手機數據庫中的音頻文件，這就要用到Cursor了，用它來存儲音頻文件，關於Cursor的用用法這裏不做過多解釋，像多瞭解的直接百度，通過SQLiteDatabase中的query方法來獲取，query有5個參數Uri uri,String [] projection,String selection,String  []selectionargs,sortOrder,這裏邊最重要的就是Uri了，它是一個明確的量，MediaStore.Audio.Media.EXTERNAL_CONTENT_URI然後sortOred就是通過那種順序來獲取，有時間，大小，等，大家可以按照自己需要去選擇。其它的可以不去用它，一般直接賦null。下面附上代碼。

public class MusicLoader {
    public  List<Song> musicList = new ArrayList<Song>();
    private ContentResolver contentResolver;
    private Uri contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    private String projection[]={
            MediaStore.Audio.Media._ID,
            MediaStore.Audio.Media.DISPLAY_NAME,
            MediaStore.Audio.Media.DATA,
            MediaStore.Audio.Media.ALBUM,
            MediaStore.Audio.Media.ARTIST,
            MediaStore.Audio.Media.DURATION,
            MediaStore.Audio.Media.SIZE,
    };
    private String sortOrder =MediaStore.Audio.Media.ARTIST;
    public Cursor Loader(ContentResolver context){
        contentResolver = context;
        Cursor cursor = contentResolver.query(contentUri, projection, null, null, sortOrder);
        if(cursor.equals(null)){
            System.out.println("There is no songs");
        }
        else if(!cursor.moveToFirst()){
            System.out.println("False");
        }
        else{
            int disPlayNameCol = cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME);
            int albumCol = cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM);
            int idCol = cursor.getColumnIndex(MediaStore.Audio.Media._ID);
            int timeCol = cursor.getColumnIndex(MediaStore.Audio.Media.DURATION);
            int sizeCol = cursor.getColumnIndex(MediaStore.Audio.Media.SIZE);
            int artistCol = cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST);
            int uriCol = cursor.getColumnIndex(MediaStore.Audio.Media.DATA);
            do{
                String Title = cursor.getString(disPlayNameCol);
                String Album = cursor.getString(albumCol);
                double Id = cursor.getDouble(idCol);
                double Time = cursor.getDouble(timeCol);
                double Size = cursor.getDouble(sizeCol);
                String Artist = cursor.getString(artistCol);
                String Uri = cursor.getString(uriCol);


                Song song = new Song(Id,Title,Artist,Album);
                song.setMusicid(Id);
                song.setMusictime(Time);
                song.setMusicSize(Size);
                song.setMusicUri(Uri);
                song.setMusicName(Title);
                song.setMusicAlbum(Album);
                song.setMusicArtist(Artist);
                musicList.add(song);
            } while(cursor.moveToNext());
        }
        return contentResolver.query(contentUri, projection, null, null, sortOrder);
    }
    public MusicLoader(){}


    public List<Song> getMusicList(){
        return musicList;
    }


    public String getUri(Cursor cursor,int pos) {
        cursor.moveToPosition(pos);
        String uri = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
        return uri;
    }


    public int playNextMusic(int count,int pos,List list){
        if(count == 1||count == 2){
            if(pos == list.size()){
                pos = 0;
            }else {
                pos++;
            }
        }else {
            pos = (int) (Math.random() * list.size());
        }
        return pos;
    }
    public void play(Intent intent){
        String uri;
        if(MusicService.mp != null && intent.getStringExtra("play").equals("play")){
            if (MusicService.mp.isPlaying()) {
                MusicService.mp.pause();
            } else {
                MusicService.mp.start();
            }
        }else {
            try {
                if (null != MusicService.mp) {
                    MusicService.mp.release();
                }
                MusicService.mp = new MediaPlayer();
                uri = intent.getStringExtra("uri");
                MusicService.mp.setDataSource(uri);
                MusicService.mp.prepare();
            } catch (IOException e) {
                e.printStackTrace();
            }
            MusicService.mp.start();
        }
    }
}

通過上面的操作就可以把手機裏的音頻文件添加到musicList這個集合中了（要事先把歌曲Song的這個類封裝好）。

public class Song {
    private double musicId;
    private double musicTime;
    private double musicSize;
    private String musicUri;
    private String musicName;
    private String musicArtist;
    private String musicAlbum;

    public Song(double id, String musicName, String musicArtist,String musicAlbum){
        this.musicId = id;
        this.musicName = musicName;
        this.musicArtist = musicArtist;
        this.musicAlbum = musicAlbum;
    }
    public double getMusicid(){
        return musicId;
    }
    public double getMusictime(){
        return musicTime;
    }
    public double getMusicSize(){
        return musicSize;
    }
    public String getMusicUri(){
        return musicUri;
    }
    public String getMusicName(){
        return musicName;
    }
    public String getMusicArtist(){
        return musicArtist;
    }
    public String getMusicAlbum() {
        return musicAlbum;
    }
    public void setMusicid(double musicIdd){
        this.musicId = musicId;
    }
    public void setMusictime(double musictime){
        this.musicTime = musictime;
    }
    public void setMusicSize(double musicSize){
        this.musicSize = musicSize;
    }
    public void setMusicUri(String musicUri){
        this.musicUri = musicUri;
    }
    public void setMusicName(String musicName){
        this.musicName = musicName;
    }
    public void setMusicArtist(String musicArtist){
        this.musicArtist = musicArtist;
    }
    public void setMusicAlbum(String musicAlbum) {
        this.musicAlbum = musicAlbum;
    }
}

        以列表的形式把歌曲顯示出來，前邊已經把音頻文件存放到musicList這個集合中了，現在就要把它們顯示在列表中，這就要用到Adapter類了，直接上代碼。

public class Adapter extends BaseAdapter {
    private List<Song> musicList;
    private LayoutInflater inflater;
    public Adapter (Context context,List<Song> musicList){
        this.musicList = musicList;
        this.inflater =LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return musicList.size();
    }

    @Override
    public Object getItem(int position) {
        return musicList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        Song song = musicList.get(position);
        LinearLayout listView = (LinearLayout)inflater.inflate(R.layout.local,null);

        TextView musicName = (TextView)listView.findViewById(R.id.musicName);
        musicName.setText(song.getMusicName());

        TextView musicArtist = (TextView)listView.findViewById(R.id.musicArtist);
        musicArtist.setText(song.getMusicArtist());

        return listView;
    }
}
public class Local extends Activity {
    public int pos;
    public long count;
    public View v;
    public String Uri;
    public Button pause;
    public Button next;
    public Button disPlay;
    public Cursor cursor;
    public ListView listView;
    MusicLoader ML = new MusicLoader();
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.listview);
        pause = (Button)findViewById(R.id.pause);
        if(MusicService.mp != null){
            if(MusicService.mp.isPlaying()){
                pause.setBackground(getResources().getDrawable(R.drawable.pause));
            }else{
                pause.setBackground(getResources().getDrawable(R.drawable.play));
            }
        }
        cursor = ML.Loader(getContentResolver());
        disPlay = (Button)findViewById(R.id.display);
        next = (Button)findViewById(R.id.next);
        Listener listener = new Listener();
        disPlay.setOnClickListener(listener);
        pause.setOnClickListener(listener);
        next.setOnClickListener(listener);

        listView = (ListView) findViewById(R.id.lv);
        ListListener listListener = new ListListener();
        listView.setOnItemClickListener(listListener);
        Adapter adapter = new Adapter(getApplicationContext(), ML.getMusicList());
        listView.setAdapter(adapter);

    }

    public class ListListener implements AdapterView.OnItemClickListener {

        @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
        public void onItemClick(AdapterView<?> parent, View view, int position, long id){
            /*
            int musicName = cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME);
            int artist = cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST);
            */
            pause.setBackground(getResources().getDrawable(R.drawable.pause));
            v = view; pos = position; count = id;
            Uri = ML.getUri(cursor,pos);
            Intent intent = new Intent(Local.this, MusicService.class);
            intent.putExtra("uri", Uri);
            intent.putExtra("play","pause");
            if(MusicService.mp != null){
                if(MusicService.mp.isPlaying()){
                    MusicService.mp.stop();
                }
            }
            startService(intent);
        }
    }
    public class Listener implements View.OnClickListener {

        @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
        @Override
        public void onClick(View v) {
            if (v.getId() == R.id.display) {
                disPlay.setBackgroundColor(1);
                Intent intent = new Intent(Local.this, Play.class);
                startActivity(intent);
            }
            if (v.getId() == R.id.pause) {
                int pos = (int) (Math.random() * ML.getMusicList().size());
                Uri = ML.getUri(cursor, pos);
                Intent intent = new Intent(Local.this, MusicService.class);
                intent.putExtra("uri", Uri);
                intent.putExtra("pos", pos);
                intent.putExtra("play", "play");
                if (MusicService.mp != null) {
                    if (MusicService.mp.isPlaying()) {
                        v.setBackground(getResources().getDrawable(R.drawable.play));
                    } else {
                        v.setBackground(getResources().getDrawable(R.drawable.pause));
                    }
                } else
                    v.setBackground(getResources().getDrawable(R.drawable.pause));
                startService(intent);
            }
            if (v.getId() == R.id.next) {
                pause.setBackground(getResources().getDrawable(R.drawable.pause));
                pos = ML.playNextMusic(Play.getCount(), pos, ML.getMusicList());
                Uri = ML.getUri(cursor, pos);
                Intent intent = new Intent(Local.this, MusicService.class);
                intent.putExtra("uri", Uri);
                intent.putExtra("pos", pos);
                intent.putExtra("play", "pause");
                if (MusicService.mp != null) {
                    MusicService.mp.stop();
                }
                startService(intent);
            }
        }
    }
}

        接下來就是播放了，最激動的時候播放這裏一定儘量用Service實現,不然當你退出程序時，它就不會播放了。

public class MusicService extends Service {
    public static MediaPlayer mp;
    public Intent intent;
    MusicLoader ML = new MusicLoader();
    String uri = null;
    Message message = new Message();
    Cursor cursor;
    int pos = 0;
    android.os.Handler handler = new android.os.Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            int i = (int)msg.obj ;
            if(i == 1){
                ML.play(intent);
                if (mp.getDuration() == mp.getCurrentPosition()) {
                    cursor = ML.Loader(getContentResolver());
                    pos = ML.playNextMusic(Play.getCount(),intent.getIntExtra("pos",pos),ML.getMusicList());
                    uri = ML.getUri(cursor,pos);
                    message.obj = 1;
                    handler.sendMessage(message);
                }
            }
        }
    };
    public IBinder onBind(Intent intent) {
        return null;
    }
    public void onCreate(){
        super.onCreate();
    }
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    public int onStartCommand(Intent intent,int flags,int startId){
        this.intent = intent;
        ML.play(intent);
        if (mp.getDuration() == mp.getCurrentPosition()) {
            cursor = ML.Loader(getContentResolver());
            pos = ML.playNextMusic(Play.getCount(),intent.getIntExtra("pos",pos),ML.getMusicList());
            uri = ML.getUri(cursor,pos);
            message.obj = 1;
            handler.sendMessage(message);
        }
        return 1;
    }
    public void onDestroy(){
        super.onDestroy();
        mp.release();
        stopSelf();
    }
}

到這裏音樂播放的基本功能就實現了，其實還有好多地方寫的不是太完善，有很多不足之處，所以筆者還是要再優化的的,希望對大家能有所幫助。