Android - 如何同步录制的两个音频文件和一个MP3文件

Question

我有一个示例应用程序，当我按下“开始”按钮时，它会启动MediaRecorder和MediaPlayer作为录制音乐的指导音乐。然后在按下“停止”按钮后，它将保存录制的音频。 然后，我有第三个按钮，可播放录制的音频和指南音频。问题是它们不同步。引导音频在录制的音频之前播放。

我的代码：

    public class MainActivity extends Activity {

         MediaRecorder recorder;
         MediaPlayer mediaPlayer;
         MediaPlayer mediaRecorded = new MediaPlayer();;
          File audiofile = null;
          private static final String TAG = "SoundRecordingActivity";
          private View startButton;
          private View stopButton;
          private View playButton;
          private View stopPlaybackButton;
          private Uri uri;

          @Override
          public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            startButton = findViewById(R.id.start);
            stopButton = findViewById(R.id.stop);
            playButton = findViewById(R.id.play);
            stopPlaybackButton = findViewById(R.id.stop_all);
          }

          public void startRecording(View view) throws IOException {

            startButton.setEnabled(false);
            stopButton.setEnabled(true);
            playButton.setEnabled(false);

            mediaPlayer = MediaPlayer.create(this, R.raw.old_mac);

            File sampleDir = Environment.getExternalStorageDirectory();
            try {
              audiofile = File.createTempFile("sound", ".mp4", sampleDir);
            } catch (IOException e) {
              Log.e(TAG, "sdcard access error");
              return;
            }
            recorder = new MediaRecorder();
            recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
            recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
            recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
            recorder.setOutputFile(audiofile.getAbsolutePath());
            recorder.prepare();
            recorder.start();
            mediaPlayer.start();
          }

          public void stopRecording(View view) {
            startButton.setEnabled(true);
            stopButton.setEnabled(false);
            playButton.setEnabled(true);
            mediaPlayer.stop();
            recorder.stop();
            recorder.release();
            addRecordingToMediaLibrary();
          }

          protected void addRecordingToMediaLibrary() {
            ContentValues values = new ContentValues(4);
            long current = System.currentTimeMillis();
            values.put(MediaStore.Audio.Media.TITLE, "audio" + audiofile.getName());
            values.put(MediaStore.Audio.Media.DATE_ADDED, (int) (current / 1000));
            values.put(MediaStore.Audio.Media.MIME_TYPE, "audio/3gpp");
            values.put(MediaStore.Audio.Media.DATA, audiofile.getAbsolutePath());
            ContentResolver contentResolver = getContentResolver();

            Uri base = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            Uri newUri = contentResolver.insert(base, values);
            sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, newUri));
            Toast.makeText(this, "Added File " + newUri, Toast.LENGTH_LONG).show();

            setNewUri(newUri);

          }

          public void setNewUri(Uri uri){
              this.uri = uri;
          }

          public Uri getNewUri(){
              return this.uri;
          }

          public void playRecording(View view){
              stopPlaybackButton.setEnabled(true);
              playButton.setEnabled(false);

              mediaPlayer = MediaPlayer.create(this, R.raw.old_mac);

              try{
                  mediaRecorded.setDataSource(this, getNewUri());
                  mediaRecorded.prepare();
                  mediaRecorded.start();
                  mediaRecorded.setVolume(0, 1);


              }catch(Exception e){

              }

              mediaPlayer.start();
              mediaPlayer.setVolume(1, 0);
          }

          public void stopAll(View view){
              stopPlaybackButton.setEnabled(false);
              playButton.setEnabled(true);
              mediaPlayer.stop();
              mediaRecorded.stop();
          }

    }