HarmonyOS 前置摄像头开启

async function startPreviewOutput(cameraManager: camera.CameraManager, previewOutput: camera.PreviewOutput): Promise<void> { 
  //相机的位置数组【0：相机位置未指定；1：后置相机；2：前置相机；3：折叠太相机；】 
  let cameraArray: Array<camera.CameraDevice> = []; 
  cameraArray = cameraManager.getSupportedCameras(); 
  if (cameraArray.length == 0) { 
    console.error('no camera.'); 
    return; 
  } 
  let cameraInput: camera.CameraInput | undefined = undefined; 
  //由于需要开启前置摄像头，前置摄像头在数组中的索引位置为2 
  cameraInput = cameraManager.createCameraInput(cameraArray[2]); 
  if (cameraInput === undefined) { 
    console.error('cameraInput is undefined'); 
    return; 
  } 
  // 打开前置摄像头 
  await cameraInput.open(); 
  let session: camera.CaptureSession = cameraManager.createCaptureSession(); 
  session.beginConfig(); 
  session.addInput(cameraInput); 
  session.addOutput(previewOutput); 
  await session.commitConfig(); 
  await session.start(); 
}