android编程实现电话录音的方法

public class PhoneListenerService extends Service {
@Override
public void onCreate() {
 TelephonyManager manager = 
   (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
 //监听电话的状态
 manager.listen(new MyListener(), PhoneStateListener.LISTEN_CALL_STATE);
}
private final class MyListener extends PhoneStateListener {
 private String num;
 private MediaRecorder recorder;
 public void onCallStateChanged(int state, String incomingNumber) {
 switch (state) {
  case TelephonyManager.CALL_STATE_RINGING: /* 电话进来时 */
  num = incomingNumber;
  break;
  case TelephonyManager.CALL_STATE_OFFHOOK: /* 接起电话时 */
  try {
   File file = new File(Environment.getExternalStorageDirectory(), num + "_" + System.currentTimeMillis() + ".3gp");
   recorder = new MediaRecorder();
   recorder.setAudioSource(AudioSource.MIC);//声音采集来源(话筒)
   recorder.setOutputFormat(OutputFormat.THREE_GPP);//输出的格式
   recorder.setAudioEncoder(AudioEncoder.AMR_NB);//音频编码方式
   recorder.setOutputFile(file.getAbsolutePath());//输出方向
   recorder.prepare();
   recorder.start();
  } catch (Exception e) {
   e.printStackTrace();
  }
  break;
  case TelephonyManager.CALL_STATE_IDLE: /* 无任何状态时 */
  if (recorder != null) {
   recorder.stop();
   recorder.release();
  }
  break;
 }
 }
}
}