java - 在Android中从音频文件创建流

Question

用例是这样的，在 Android 中(在 Kit Kat 之上):从音频文件打开一个流，获取它的属性，修改内存缓冲区并播放结果。
我想知道如何 1)从音频文件正确创建流； 2) 像 javax.sound.sampled.AudioFormat 一样获取其属性( channel 、编码、长度)，但使用来自 android.media 框架的方法。
我知道如何从二进制构建一个流，向它添加音频属性然后播放它。我想做另一种方式，并使用 Android 框架的最新类从现有的声音文件头中提取这些属性( channel 、编码)。
谢谢!

Answer 1

这是完整的流媒体类使用:

public class MainActivity extends Activity implements OnClickListener,
        OnTouchListener, OnCompletionListener, OnBufferingUpdateListener {
    private Button btn_play, btn_pause, btn_stop;
    private SeekBar seekBar;
    private MediaPlayer mediaPlayer;
    private int lengthOfAudio;
    private final String URL = "http://songspkcompilations.com/indian/soulfularijit/%5BSongs.PK%5D%2012%20-%20Mickey%20Virus%20-%20Tose%20Naina.mp3";
    private static final int MINUTES_IN_AN_HOUR = 60;
    private static final int SECONDS_IN_A_MINUTE = 60;
    private final Handler handler = new Handler();
    private boolean is_loading = true;
    private boolean is_stopped = false;
    private final Runnable r = new Runnable() {
        @Override
        public void run() {
            updateSeekProgress();
        }
    };
    private TextView txtTime;
    private ProgressBar musicProgress;
    private ImageView artistImg;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initialize_Controls();
    }

    private void initialize_Controls() {
        btn_play = (Button) findViewById(R.id.btn_play);
        btn_play.setOnClickListener(this);
        btn_pause = (Button) findViewById(R.id.btn_pause);
        btn_pause.setOnClickListener(this);
        btn_pause.setEnabled(false);
        btn_stop = (Button) findViewById(R.id.btn_stop);
        btn_stop.setOnClickListener(this);
        btn_stop.setEnabled(false);

        musicProgress = (ProgressBar) findViewById(R.id.progress);
        artistImg = (ImageView) findViewById(R.id.artistImg);

        seekBar = (SeekBar) findViewById(R.id.seekBar);
        seekBar.setOnTouchListener(this);

        txtTime = (TextView) findViewById(R.id.time);

        mediaPlayer = new MediaPlayer();
        mediaPlayer.setOnBufferingUpdateListener(this);
        mediaPlayer.setOnCompletionListener(this);
    }

    @Override
    public void onBufferingUpdate(MediaPlayer mediaPlayer, int percent) {
        seekBar.setSecondaryProgress(percent);
    }

    @Override
    public void onCompletion(MediaPlayer mp) {
        btn_play.setEnabled(true);
        btn_pause.setEnabled(false);
        btn_stop.setEnabled(false);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (mediaPlayer.isPlaying()) {
            SeekBar tmpSeekBar = (SeekBar) v;
            mediaPlayer
                    .seekTo((lengthOfAudio / 100) * tmpSeekBar.getProgress());
        }
        return false;
    }

    @Override
    public void onClick(View view) {

        try {
            mediaPlayer.setDataSource(URL);
            mediaPlayer.prepare();
            lengthOfAudio = mediaPlayer.getDuration();

        } catch (Exception e) {
            // Log.e("Error", e.getMessage());
        }

        switch (view.getId()) {
        case R.id.btn_play:
            if (is_stopped) {
                is_stopped = false;
                mediaPlayer.seekTo(0);
            }
            playAudio();
            break;
        case R.id.btn_pause:
            pauseAudio();
            break;
        case R.id.btn_stop:
            stopAudio();
            break;
        default:
            break;
        }

        updateSeekProgress();
    }

    private void updateSeekProgress() {
        if (mediaPlayer.isPlaying()) {
            if (is_loading) {
                is_loading = false;
                musicProgress.setVisibility(View.GONE);
                artistImg.setVisibility(View.VISIBLE);
            }
            int progress = (int) (((float) mediaPlayer.getCurrentPosition() / lengthOfAudio) * 100);

            int remainSec = (lengthOfAudio - mediaPlayer.getCurrentPosition()) / 1000;

            seekBar.setProgress(progress);
            txtTime.setText("" + timeConversion(remainSec));

            handler.postDelayed(r, 1000);
        }
    }

    private void stopAudio() {
        if (mediaPlayer != null) {
            mediaPlayer.pause();
            is_stopped = true;
        }
        seekBar.setProgress(0);
        seekBar.setSecondaryProgress(0);
        txtTime.setText("" + timeConversion(lengthOfAudio / 1000));
        btn_play.setEnabled(true);
        btn_pause.setEnabled(false);
        btn_stop.setEnabled(false);
    }

    private void pauseAudio() {
        if (mediaPlayer != null) {
            mediaPlayer.pause();
        }
        btn_play.setEnabled(true);
        btn_pause.setEnabled(false);
    }

    private void playAudio() {
        if (mediaPlayer != null) {
            mediaPlayer.start();
        }
        btn_play.setEnabled(false);
        btn_pause.setEnabled(true);
        btn_stop.setEnabled(true);
    }

    private static String timeConversion(int totalSeconds) {
        int hours = totalSeconds / MINUTES_IN_AN_HOUR / SECONDS_IN_A_MINUTE;
        int minutes = (totalSeconds - (hoursToSeconds(hours)))
                / SECONDS_IN_A_MINUTE;
        int seconds = totalSeconds
                - ((hoursToSeconds(hours)) + (minutesToSeconds(minutes)));

        return hours + ":" + minutes + ":" + seconds;
    }

    private static int hoursToSeconds(int hours) {
        return hours * MINUTES_IN_AN_HOUR * SECONDS_IN_A_MINUTE;
    }

    private static int minutesToSeconds(int minutes) {
        return minutes * SECONDS_IN_A_MINUTE;
    }

    class PlayTask extends AsyncTask<String, Integer, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(String... params) {
            try {
                mediaPlayer.setDataSource(URL);
                mediaPlayer.prepare();
                lengthOfAudio = mediaPlayer.getDuration();

            } catch (Exception e) {
                // Log.e("Error", e.getMessage());
            }

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            playAudio();
            updateSeekProgress();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        new PlayTask().execute();
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();

        pauseAudio();
        finish();
    }
}