如何在Camera2 API中启用前置摄像头？

Question

如何在Camera2 API上启用前置摄像头。有人可以帮忙吗？ 我有这个Camera2 API代码。这仅设置了设备的主摄像头，我希望在单击按钮时启用前后摄像头。什么是LENS_FACING_FRONT ，我是Android编程的新手。

 private void setUpCameraOutputs(int width, int height) {
    Activity activity = getActivity();
    CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    try {
        for (String cameraId : manager.getCameraIdList()) {
            CameraCharacteristics characteristics
                    = manager.getCameraCharacteristics(cameraId);

            // We don't use a front facing camera in this sample.
            Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
            if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
                continue;
            }

            StreamConfigurationMap map = characteristics.get(
                    CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            if (map == null) {
                continue;
            }

            // For still image captures, we use the largest available size.
            Size largest = Collections.max(
                    Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
                    new CompareSizesByArea());
            mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
                    ImageFormat.JPEG, /*maxImages*/2);
            mImageReader.setOnImageAvailableListener(
                    mOnImageAvailableListener, mBackgroundHandler);

            // Danger, W.R.! Attempting to use too large a preview size could  exceed the camera
            // bus' bandwidth limitation, resulting in gorgeous previews but the storage of
            // garbage capture data.
            mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
                    width, height, largest);

            // We fit the aspect ratio of TextureView to the size of preview we picked.
            int orientation = getResources().getConfiguration().orientation;
            if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
                mTextureView.setAspectRatio(
                        mPreviewSize.getWidth(), mPreviewSize.getHeight());
            } else {
                mTextureView.setAspectRatio(
                        mPreviewSize.getHeight(), mPreviewSize.getWidth());
            }

            mCameraId = cameraId;
            return;
        }
    } catch (CameraAccessException e) {
        e.printStackTrace();
    } catch (NullPointerException e) {
        // Currently an NPE is thrown when the Camera2API is used but not supported on the
        // device this code runs.
        ErrorDialog.newInstance(getString(R.string.camera_error))
                .show(getChildFragmentManager(), FRAGMENT_DIALOG);
    }
}

Answer 1

我们可以使用CameraManager来迭代系统中可用的所有摄像机，每个摄像机都有一个指定的cameraId。 使用cameraId，我们可以获得指定摄像头设备的属性。 这些属性由CameraCharacteristics类表示。 可以查询“是前置摄像头还是后置摄像头”，“支持输出分辨率”之类的信息。

您可以在此处获取官方示例应用程序

在Google Git存储库中找到的该示例将演示如何使用Camera2 API在新的棉花糖中启动相机之前检查权限

请看一下这篇文章，以获得更多有关它的信息。