在Android 11中，应用程序在后台运行时无法使用前台服务中的录音功能。解决此问题的一种方法是使用MediaRecorder API并执行后台录音。以下是示例代码：

1.添加适当的权限到AndroidManifest.xml文件中：

2.在服务（Service）类中实例化MediaRecorder并设置相应的录音属性：

private MediaRecorder recorder; private static String outputFile = null;

public void startRecording() { recorder = new MediaRecorder(); recorder.setAudioSource(MediaRecorder.AudioSource.MIC); recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC); recorder.setOutputFile(getOutputFile()); try { recorder.prepare(); } catch (IOException e) { Log.e("TAG", "prepare() failed"); } recorder.start(); } public void stopRecording() { recorder.stop(); recorder.release(); recorder = null; }

private String getOutputFile() { if (outputFile == null) { File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/MyApp/"); if (!dir.exists()) { dir.mkdirs(); } outputFile = dir.getAbsolutePath() + "/" + new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()) + ".mp4"; } return outputFile; }

3.在服务类中添加以下代码：

private NotificationManager notificationManager;

@Override public void onCreate() { super.onCreate(); notificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); }

@Override public int onStartCommand(Intent intent, int flags, int startId) { Notification notification = new Notification.Builder(this, YOUR_CHANNEL_ID) .setContentTitle("My Recording Service") .setContentText("Recording...") .setSmallIcon(R.drawable.ic_launcher) .build(); startForeground(1, notification); startRecording(); return START_STICKY;