Android Mediaplayer: setDataSource issue for downloaded media file

问题

I have an application that will record and play audio files. Some of the audio files are downloaded using simple standard http downloads using httpclient. It worked like a charm for a long time. Now all of a sudden I cannot play the files I download. It fails with this stack. I store the files on the SDCard and I experience the problem both on a handset and a USB connected device.

I have checked that the downloaded file is cool on the server, and I can play it without any issues.

These are the code snippets I use ( I know that recordingFile is a valid path for the file).

    // inside the activity class
    private void playRecording() throws IOException{
        File recordingFile = new File(recordingFileName);
        FileInputStream recordingInputStream = new FileInputStream(recordingFile); 
        audioMediaPlayer.playAudio(recordingInputStream);
    }

Here is the media player code:

    // inside my media player class which handles the recordings
    public void playAudio(FileInputStream audioInputStream) throws IOException {
        mediaPlayer.reset();
        mediaPlayer.setDataSource(audioInputStream.getFD());
        mediaPlayer.prepare();
        mediaPlayer.start();
}

Here is the exception:

E/MediaPlayerService(  555): offset error
E/MediaPlayer(  786): Unable to to create media player
W/System.err(  786): java.io.IOException: setDataSourceFD failed.: status=0x80000000
W/System.err(  786):    at android.media.MediaPlayer.setDataSource(Native Method)
W/System.err(  786):    at android.media.MediaPlayer.setDataSource(MediaPlayer.java:632)
W/System.err(  786):    at net.xxx.xxx.AudioMediaPlayer.playAudio(AudioMediaPlayer.java:69)
W/System.err(  786):    at net.xxx.xxx.Downloads.playRecording(Downloads.java:299)
W/System.err(  786):    at net.xxx.xxx.Downloads.access$0(Downloads.java:294)
W/System.err(  786):    at net.xxx.xxx.Downloads$1.onClick(Downloads.java:135)

I have tried seeking some answer of the offset error, but not really clear what this issue might be.

PS I download the file with this code:

    public FileOutputStream executeHttpGet(FileOutputStream fileOutputStream) throws ClientProtocolException, IOException{
        try {     
            // Execute HTTP Post Request  
            httpResponse = httpClient.execute(httpPost, localContext);
            int status = httpResponse.getStatusLine().getStatusCode();

            // we assume that the response body contains the error message
            if (status != HttpStatus.SC_OK) {
                ByteArrayOutputStream ostream = new ByteArrayOutputStream();
                httpResponse.getEntity().writeTo(ostream);
                fileOutputStream = null;
            } else {
                InputStream content = httpResponse.getEntity().getContent();

                byte[] buffer = new byte[1024];
                int len = 0;
                while ( (len = content.read(buffer)) > 0 ) {
                    fileOutputStream.write(buffer,0, len);
                }
                fileOutputStream.close();
                content.close(); // this will also close the connection
            }

        } catch (ClientProtocolException e1) {  
            // TODO Auto-generated catch block 
            e1.printStackTrace();
            fileOutputStream = null;
        } catch (IOException e2) {  
            // TODO Auto-generated catch block  
            e2.printStackTrace();
            fileOutputStream = null;
        }
        return fileOutputStream;
    }

回答1:

I solved it on my own. As I put it my comment above the solution was this:

When I refactored part of the code I made a typo on a hash code I use to allow downloads and not. Unfortunately I didn't have the proper catch when I downloaded the file forcing the file to be empty. Basically I send a bad request header if you try to retrieve a file without a proper activation code.

The culprit was here:

        if (status != HttpStatus.SC_OK) {
            ByteArrayOutputStream ostream = new ByteArrayOutputStream();
            httpResponse.getEntity().writeTo(ostream);
            fileOutputStream = null;
        } else {
            InputStream content = httpResponse.getEntity().getContent();

            byte[] buffer = new byte[1024];
            int len = 0;
            while ( (len = content.read(buffer)) > 0 ) {
                fileOutputStream.write(buffer,0, len);
            }
            fileOutputStream.close();
           content.close(); // this will also close the connection
    }

For cases where the status code came back a as bad (i.e. bad request header for blocked accesses). What I missed was to capture the case of a null pointer there and that caused a SQLite entry to be updated claiming to the app that the download was successful but yet it wasn't.

Lesson learnt: Always put in the null checks for these cases even for prototypes. :-)

回答2:

First, make sure your device is not mounted. Either Android or the host PC can access the SD card, but not both simultaneously.

Second, it is unclear why you are using a FileInputStream and getFD(). Just pass the path to the file on the SD card to the MediaPlayer (e.g., new File(Environment.getExternalStorageDirectory(), "yourfile.mp3")) and let the player open the file.

来源：https://stackoverflow.com/questions/2798227/android-mediaplayer-setdatasource-issue-for-downloaded-media-file