在Android相机应用中进行人脸检测和距离测量的问题，可以使用Camera2 API实现。以下是一个简单的示例代码：

1. 设置摄像头时首先需要创建一个CameraManager对象，获取到设备上可用的相机列表

CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE); String cameraId = manager.getCameraIdList()[0];

2. 创建一个CameraDevice对象，实现相机的打开和关闭

manager.openCamera(cameraId, new CameraDevice.StateCallback() { @Override public void onOpened(CameraDevice camera) { mCameraDevice = camera; } @Override public void onDisconnected(CameraDevice camera) { camera.close(); mCameraDevice = null; } @Override public void onError(CameraDevice camera, int error) { camera.close(); mCameraDevice = null; } }, null);

3. 建立CameraCaptureSession会话，准备开始预览操作

mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() { @Override public void onConfigured(CameraCaptureSession cameraCaptureSession) { if (mCameraDevice == null) { return; } mCaptureSession = cameraCaptureSession;

// 开始预览操作，可以创建一个CaptureRequest.Builder对象进行自定义设置

CaptureRequest.Builder previewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE); 

//将会话与预览界面关联

previewBuilder.addTarget(surfaceHolder.getSurface());

// 开始预览

CaptureRequest previewRequest = previewBuilder.build();
mCaptureSession.setRepeatingRequest(previewRequest, null, null);

} }, null);

4. 开始人脸检测，设置相机的FaceDetectionListener

CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId); int[] faceDetectModes = characteristics.get(CameraCharacteristics.STATISTICS_INFO_AVAILABLE_FACE_DETECT_MODES); int faceDetectMode = faceDetectModes[0]; int maxFaceCount = characteristics.get(CameraCharacteristics.STATISTICS_INFO_MAX_FACE_COUNT);

mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() { @Override public void onConfigured(CameraCaptureSession cameraCaptureSession) { mCaptureSession = cameraCaptureSession; try { CaptureRequest.Builder builder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); builder.addTarget(surface);

    // 设置人