使用MediaRecorder仅录制音频

<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

private void checkPermissions() {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED ||
            ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.RECORD_AUDIO, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);
    }
}

private MediaRecorder mediaRecorder;
private String outputFile;

private void initMediaRecorder() {
    mediaRecorder = new MediaRecorder();
    mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    outputFile = Environment.getExternalStorageDirectory().getAbsolutePath() + "/recorded_audio.3gp";
    mediaRecorder.setOutputFile(outputFile);
}

private void startRecording() {
    try {
        initMediaRecorder();
        mediaRecorder.prepare();
        mediaRecorder.start();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private void stopRecording() {
    mediaRecorder.stop();
    mediaRecorder.release();
    mediaRecorder = null;
}