我怎么能解决这个问题？

MediaRecorder _recorder = new MediaRecorder();


public void start() throws IOException {
    try {
        String state = android.os.Environment.getExternalStorageState();
        if (!state.equals(android.os.Environment.MEDIA_MOUNTED)) {
            throw new IOException("SD Card is not mounted.  It is " + state
                    + ".");
        }

        // make sure the directory we plan to store the recording in exists
        File directory = new File(Environment.getExternalStorageDirectory().getAbsolutePath()
                + "/sam.wav").getParentFile();
        if (!directory.exists() && !directory.mkdirs()) {
            throw new IOException("Path to file could not be created.");
        }


        _recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL );
        _recorder.setOutputFormat(MediaRecorder.OutputFormat.DEFAULT);
        _recorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);
        setOutputFile(Environment.getExternalStorageDirectory().getAbsolutePath()
                + "/test.wav");
        _recorder.prepare();
        _recorder.start();

    } catch (Exception e) {
        e.printStackTrace();
    }
}