你好，我想用mediaRecorder录音。我要保存的格式是amr。this.mediaRecorder=newMediaRecorder();this.mediaRecorder.setAudioChannels(1);this.mediaRecorder.setAudioSamplingRate(8000);this.mediaRecorder.setAudioEncodingBitRate(16);this.mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);this.mediaRecorder.setOutpu