对于录制音频类的应用，我们需要关注该应用的音频流的状态以做出相应的操作，比如监听到状态为结束时，及时提示用户录制已结束。

👉🏻 读取/监听音频流状态变化

鸿蒙媒体开发系列08——AudioCapturer录制音频可以通过以下两种方式查看音频流状态的变化：

方法1：直接查看AudioCapturer的state：

let audioCapturerState = audioCapturer.state;
console.info(`Current state is: ${audioCapturerState }`)

方法2：注册stateChange监听AudioCapturer的状态变化：

audioCapturer.on('stateChange', (capturerState) => {
  console.info(`State change to: ${capturerState}`)
});

获取state后可对照AudioState来进行相应的操作，比如显示录制结束的提示等。

AudioState状态如下：

👉🏻 读取/监听录制流的变化

如果部分应用需要查询获取所有音频流的变化信息，可以通过AudioStreamManager读取或监听所有音频流的变化。

如下为音频流管理调用关系图：

在进行应用开发的过程中，开发者需要使用getStreamManager()创建一个AudioStreamManager实例，进而通过该实例管理音频流。开发者可通过调用on('audioCapturerChange')监听音频流的变化，在音频流状态变化、设备变化时获得通知，同时可通过off('audioCapturerChange')取消相关事件的监听。另外，开发者可以通过主动调用getCurrentAudioCapturerInfoArray()查询录制流的唯一ID、录制流客户端的UID、以及流状态等信息。

☆ 主要的开发步骤

1、创建AudioStreamManager实例。

在使用AudioStreamManager的API前，需要使用getStreamManager()创建一个AudioStreamManager实例。

import audio from '@ohos.multimedia.audio';
let audioManager = audio.getAudioManager();
let audioStreamManager = audioManager.getStreamManager();

2、使用on('audioCapturerChange')监听音频录制流更改事件。如果音频流监听应用需要在音频录制流状态变化、设备变化时获取通知，可以订阅该事件。

audioStreamManager.on('audioCapturerChange', (AudioCapturerChangeInfoArray) =>  {
  for (let i = 0; i < AudioCapturerChangeInfoArray.length; i++) {
    console.info(`## CapChange on is called for element ${i} ##`);
    console.info(`StreamId for ${i} is: ${AudioCapturerChangeInfoArray[i].streamId}`);
    console.info(`Source for ${i} is: ${AudioCapturerChangeInfoArray[i].capturerInfo.source}`);
    console.info(`Flag  ${i} is: ${AudioCapturerChangeInfoArray[i].capturerInfo.capturerFlags}`);
    let devDescriptor = AudioCapturerChangeInfoArray[i].deviceDescriptors;
    for (let j = 0; j < AudioCapturerChangeInfoArray[i].deviceDescriptors.length; j++) {
      console.info(`Id: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].id}`);
      console.info(`Type: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].deviceType}`);
      console.info(`Role: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].deviceRole}`);
      console.info(`Name: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].name}`);
      console.info(`Address: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].address}`);
      console.info(`SampleRates: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].sampleRates[0]}`);
      console.info(`ChannelCounts ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].channelCounts[0]}`);
      console.info(`ChannelMask: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].channelMasks}`);
    }
  }
});

3、（可选）使用off('audioCapturerChange')取消监听音频录制流变化。

audioStreamManager.off('audioCapturerChange');
console.info('CapturerChange Off is called');

4、（可选）使用getCurrentAudioCapturerInfoArray()获取当前音频录制流的信息。

该接口可获取音频录制流唯一ID，音频录制客户端的UID，音频状态以及音频捕获器的其他信息。

async function getCurrentAudioCapturerInfoArray(){
  await audioStreamManager.getCurrentAudioCapturerInfoArray().then( function (AudioCapturerChangeInfoArray) {
    console.info('getCurrentAudioCapturerInfoArray **** Get Promise Called ****');
    if (AudioCapturerChangeInfoArray != null) {
      for (let i = 0; i < AudioCapturerChangeInfoArray.length; i++) {
        console.info(`StreamId for ${i} is: ${AudioCapturerChangeInfoArray[i].streamId}`);
        console.info(`Source for ${i} is: ${AudioCapturerChangeInfoArray[i].capturerInfo.source}`);
        console.info(`Flag  ${i} is: ${AudioCapturerChangeInfoArray[i].capturerInfo.capturerFlags}`);
        for (let j = 0; j < AudioCapturerChangeInfoArray[i].deviceDescriptors.length; j++) {
          console.info(`Id: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].id}`);
          console.info(`Type: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].deviceType}`);
          console.info(`Role: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].deviceRole}`);
          console.info(`Name: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].name}`);
          console.info(`Address: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].address}`);
          console.info(`SampleRates: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].sampleRates[0]}`);
          console.info(`ChannelCounts ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].channelCounts[0]}`);
          console.info(`ChannelMask: ${i} : ${AudioCapturerChangeInfoArray[i].deviceDescriptors[j].channelMasks}`);
        }
      }
    }
  }).catch((err) => {
    console.error(`Invoke getCurrentAudioCapturerInfoArray failed, code is ${err.code}, message is ${err.message}`);
  });
}