Create FileDescriptor on Android without first opening file

In Android, is it possible to generate a FileDescriptor directly from a byte array without opening the file first?

In Android 2.2, I generate a MIDI file on the fly and then play it back using MediaPlayer. I have included the text of the Main.java file that does this successfully below. So far so good.

However, this process first causes ...

FileOutputStream outputStream = openFileOutput(file, MODE_PRIVATE);
outputStream.write(byteStream);
outputStream.close();

      

        
        
        
      

    

... to write the file and then calls ...

FileInputStream inputStream = new FileInputStream(midifile);
FileDescriptor fileDescriptor = inputStream.getFD();

      

        
        
        
      

    

... to read it before calling:

mediaPlayer.setDataSource(fileDescriptor);

      

        
        
        
      

    

It seems to me that this is wasteful. Can I create a FileDescriptor directly from byteArray so that the MIDI stream can be played right away?

== Working code ==

package com.example.midi;

import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;

public class Main extends Activity {

  private String file = "midi.mid";
  private MediaPlayer mediaPlayer;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mediaPlayer = new MediaPlayer();
    mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);

    createNewMIDIFile();
    playNewMIDIFile();
  }

  public void createNewMIDIFile() {
    Integer[] stream = new Integer[]{
        //
        0x4d, 0x54, 0x68, 0x64, // MThd = MIDI file designator
        0x00, 0x00, 0x00, 0x06, // Standard MIDI File (SMF)
        0x00, 0x01, 0x00, 0x02, // multiple-track format: 2 tracks
        0x00, 0x40, // 64 ticks per beat (quarter note)
        0x4D, 0x54, 0x72, 0x6B, // Header for track 1
        0x00, 0x00, 0x00, 0x0B, // 11  bytes to describe the track
        0x00, 0xFF, 0x51, 0x03, // set tempo:
        0x0F, 0x42, 0x40, //  1,000,000 microseconds / beat: 60 bpm
        0x00, 0xFF, 0x2F, 0x00, // End of track 1
        0x4D, 0x54, 0x72, 0x6B, // Header for track 2
        0x00, 0x00, 0x00, 0x0F, // 15 bytes to describe the track
        0x00, // Immediately
        0xC1, 0x01, // change instrument for track 2 to piano
        0x00, // Immediately
        0x91, 0x3C, 0x7F, // play middle C with a velocity of 127
        0x30, // 48 ticks later (dotted eighth note)
        0x81, 0x3C, 0x00, // stop playing the middle C
        0x00, 0xFF, 0x2F, 0x00 // End of track 2
    };

    int length = stream.length;
    byte[] byteStream = new byte[length];
    for (int ii = 0; ii < length; ii++) {
      byteStream[ii] = (byte) (stream[ii] % 256);
    }

    try {
      FileOutputStream outputStream = openFileOutput(file, MODE_PRIVATE);
      outputStream.write(byteStream);
      outputStream.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public void play(View view) {
  /* Triggered by a button defined in activity_main.xml as 
  <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="play"
    android:text="Play MIDI" />
  */
    playNewMIDIFile();
  }

  public void playNewMIDIFile() {
    try {
      String filename = getFilesDir() + "/" + file;
      File midifile = new File(filename);
      FileInputStream inputStream = new FileInputStream(midifile);
      FileDescriptor fileDescriptor = inputStream.getFD();
      mediaPlayer.reset();
      mediaPlayer.setDataSource(fileDescriptor);
      inputStream.close();
      mediaPlayer.prepare();
      mediaPlayer.start();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

      

        
        
        
      

    

For more on creating a MIDI file on the fly, see kevinboone.net , skytopia and sonicspot