通过 ARCore 共享相机访问权限

本开发者指南将逐步介绍如何让您的应用在通过 Android Camera2 API 对摄像头的专属控制权和与 ARCore 共享摄像头访问权限之间无缝切换。

本主题假设您:

构建和运行示例应用

当您构建并运行 Shared Camera Java 示例应用时,它会创建一个支持共享摄像头访问权限的 ARCore 会话。应用在非 AR 模式下启动,并且 ARCore 暂停。

当应用在非 AR 模式下运行时,相机查看器会显示深褐色颜色效果。切换到 AR 模式后,当应用通过恢复暂停的会话将摄像头控制权交还给 ARCore 时,棕褐色效果会关闭。

您可以使用应用中的 AR 开关来更改模式。在预览期间,两种模式都会显示 Camera2 拍摄的连续帧的数量。

如需构建并运行共享相机 Java 示例应用,请执行以下操作:

  1. 下载并解压缩 Google ARCore SDK for Android

  2. 打开 samples/shared_camera_java 项目。

  3. 确保您的 Android 设备通过 USB 连接到开发机器。如需了解详细信息,请参阅 ARCore 支持的设备

  4. 在 Android Studio 中,点击 Run

  5. 选择您的设备作为部署目标,然后点击 OK 以在设备上启动示例应用。

  6. 在设备上,确认您允许应用拍摄照片和录制视频。

  7. 如果系统提示您更新,请更新或安装最新版本的 ARCore。

  8. 使用 AR 开关可在非 AR 模式和 AR 模式之间切换。

允许应用与 ARCore 共享摄像头访问权限的概览

请按照以下步骤在您的应用中使用 ARCore 实现共享摄像头访问权限。所有代码段均可在 shared_camera_java 示例的 SharedCameraActivity.java 中找到。

请求 CAMERA 权限

为了能够使用设备的相机,用户必须向您的应用授予 CAMERA 权限。ARCore 示例包含一个 CameraPermissionHelper,它提供了用于为您的应用请求正确权限的实用程序。

Java

protected void onResume() {
  // Request the camera permission, if necessary.
  if (!CameraPermissionHelper.hasCameraPermission(this)) {
      CameraPermissionHelper.requestCameraPermission(this);
  }
}

Kotlin

override fun onResume() {
  // Request the camera permission, if necessary.
  if (!CameraPermissionHelper.hasCameraPermission(this)) {
    CameraPermissionHelper.requestCameraPermission(this)
  }
}

确保 ARCore 已安装并且是最新版本

必须先安装 ARCore 并将其更新为最新版本,然后才能使用。以下代码段展示了如何请求安装 ARCore(如果 ARCore 尚未安装在设备上)。

Java

boolean isARCoreSupportedAndUpToDate() {
  // Make sure that ARCore is installed and supported on this device.
  ArCoreApk.Availability availability = ArCoreApk.getInstance().checkAvailability(this);
  switch (availability) {
    case SUPPORTED_INSTALLED:
      return true;

    case SUPPORTED_APK_TOO_OLD:
    case SUPPORTED_NOT_INSTALLED:
        // Requests an ARCore installation or updates ARCore if needed.
        ArCoreApk.InstallStatus installStatus = ArCoreApk.getInstance().requestInstall(this, userRequestedInstall);
        switch (installStatus) {
          case INSTALL_REQUESTED:
            return false;
          case INSTALLED:
            return true;
        }
      return false;

    default:
      // Handle the error. For example, show the user a snackbar that tells them
      // ARCore is not supported on their device.
      return false;
  }
}

Kotlin

// Determine ARCore installation status.
// Requests an ARCore installation or updates ARCore if needed.
fun isARCoreSupportedAndUpToDate(): Boolean {
  when (ArCoreApk.getInstance().checkAvailability(this)) {
    Availability.SUPPORTED_INSTALLED -> return true

    Availability.SUPPORTED_APK_TOO_OLD,
    Availability.SUPPORTED_NOT_INSTALLED -> {
      when(ArCoreApk.getInstance().requestInstall(this, userRequestedInstall)) {
        InstallStatus.INSTALLED -> return true
        else -> return false
      }
    }

    else -> {
      // Handle the error. For example, show the user a snackbar that tells them
      // ARCore is not supported on their device.
      return false
    }
  }
}

创建支持摄像头共享的 ARCore 会话

这涉及创建会话以及存储 ARCore 共享摄像头的引用和 ID:

Java

// Create an ARCore session that supports camera sharing.
sharedSession = new Session(this, EnumSet.of(Session.Feature.SHARED_CAMERA))

// Store the ARCore shared camera reference.
sharedCamera = sharedSession.getSharedCamera();

// Store the ID of the camera that ARCore uses.
cameraId = sharedSession.getCameraConfig().getCameraId();

Kotlin

// Create an ARCore session that supports camera sharing.
sharedSession = Session(this, EnumSet.of(Session.Feature.SHARED_CAMERA))

// Store the ARCore shared camera reference.
sharedCamera = sharedSession.sharedCamera

// Store the ID of the camera that ARCore uses.
cameraId = sharedSession.cameraConfig.cameraId

(可选)告知 ARCore 有任何自定义 surface

请求额外的自定义 surface 会增加设备的性能需求。为了确保运行良好,请在用户将使用的设备上测试您的应用。

默认情况下,ARCore 会请求两个视频流:

  1. 1x YUV CPU 流,目前始终为 640x480
    ARCore 会将此数据流用于动作跟踪
  2. 1x GPU 流,通常为 1920x1080
    使用 Session#getCameraConfig() 确定当前的 GPU 流分辨率。

您可以使用 getSupportedCameraConfigs()setCameraConfig() 更改受支持设备上的 GPU 流的分辨率。

从粗略的角度来看,您应该了解:

设备类型 支持同时在线播放
高端手机
  • 2 个 YUV CPU 流,例如 640x4801920x1080
  • 1x GPU 数据流,例如 1920x1080
  • 偶尔显示 1 张高分辨率静态图片 (JPEG),例如 12MP
中端手机
  • 2 个 YUV CPU 流,例如 640x4801920x1080
  • 1x GPU 数据流,例如 1920x1080
–或–
  • 1 个 YUV CPU 流,例如 640x480 - 或 1920x1080
  • 1x GPU 数据流,例如 1920x1080
  • 偶尔显示 1 张高分辨率静态图片 (JPEG),例如 12MP

如需使用自定义 surface(例如 CPU 图片读取器 surface),请务必将其添加到需要更新的 surface(例如 ImageReader)列表中。

Java

sharedCamera.setAppSurfaces(this.cameraId, Arrays.asList(imageReader.getSurface()));

Kotlin

sharedCamera.setAppSurfaces(this.cameraId, listOf(imageReader.surface))

打开相机

使用 ARCore 封装的回调打开摄像头:

Java

// Wrap the callback in a shared camera callback.
CameraDevice.StateCallback wrappedCallback =
    sharedCamera.createARDeviceStateCallback(cameraDeviceCallback, backgroundHandler);

// Store a reference to the camera system service.
cameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);

// Open the camera device using the ARCore wrapped callback.
cameraManager.openCamera(cameraId, wrappedCallback, backgroundHandler);

Kotlin

// Wrap the callback in a shared camera callback.
val wrappedCallback = sharedCamera.createARDeviceStateCallback(cameraDeviceCallback, backgroundHandler)

// Store a reference to the camera system service.
val cameraManager = this.getSystemService(Context.CAMERA_SERVICE) as CameraManager

// Open the camera device using the ARCore wrapped callback.
cameraManager.openCamera(cameraId, wrappedCallback, backgroundHandler)

使用相机设备状态回调

在相机设备状态回调中,存储对相机设备的引用,并启动新的拍摄会话。

Java

public void onOpened(@NonNull CameraDevice cameraDevice) {
    Log.d(TAG, "Camera device ID " + cameraDevice.getId() + " opened.");
    SharedCameraActivity.this.cameraDevice = cameraDevice;
    createCameraPreviewSession();
}

Kotlin

fun onOpened(cameraDevice: CameraDevice) {
  Log.d(TAG, "Camera device ID " + cameraDevice.id + " opened.")
  this.cameraDevice = cameraDevice
  createCameraPreviewSession()
}

创建新的拍摄会话

构建新的拍摄请求。使用 TEMPLATE_RECORD 可确保捕获请求与 ARCore 兼容,并允许在运行时在非 AR 模式和 AR 模式之间无缝切换。

Java

void createCameraPreviewSession() {
  try {
    // Create an ARCore-compatible capture request using `TEMPLATE_RECORD`.
    previewCaptureRequestBuilder =
        cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);

    // Build a list of surfaces, starting with ARCore provided surfaces.
    List<Surface> surfaceList = sharedCamera.getArCoreSurfaces();

    // (Optional) Add a CPU image reader surface.
    surfaceList.add(cpuImageReader.getSurface());

    // The list should now contain three surfaces:
    // 0. sharedCamera.getSurfaceTexture()
    // 1. …
    // 2. cpuImageReader.getSurface()

    // Add ARCore surfaces and CPU image surface targets.
    for (Surface surface : surfaceList) {
      previewCaptureRequestBuilder.addTarget(surface);
    }

    // Wrap our callback in a shared camera callback.
    CameraCaptureSession.StateCallback wrappedCallback =
        sharedCamera.createARSessionStateCallback(cameraSessionStateCallback, backgroundHandler);

    // Create a camera capture session for camera preview using an ARCore wrapped callback.
    cameraDevice.createCaptureSession(surfaceList, wrappedCallback, backgroundHandler);
  } catch (CameraAccessException e) {
    Log.e(TAG, "CameraAccessException", e);
  }
}

Kotlin

fun createCameraPreviewSession() {
  try {
    // Create an ARCore-compatible capture request using `TEMPLATE_RECORD`.
    previewCaptureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD)

    // Build a list of surfaces, starting with ARCore provided surfaces.
    val surfaceList: MutableList<Surface> = sharedCamera.arCoreSurfaces

    // (Optional) Add a CPU image reader surface.
    surfaceList.add(cpuImageReader.getSurface())

    // The list should now contain three surfaces:
    // 0. sharedCamera.getSurfaceTexture()
    // 1. …
    // 2. cpuImageReader.getSurface()

    // Add ARCore surfaces and CPU image surface targets.
    for (surface in surfaceList) {
      previewCaptureRequestBuilder.addTarget(surface)
    }

    // Wrap the callback in a shared camera callback.
    val wrappedCallback = sharedCamera.createARSessionStateCallback(cameraSessionStateCallback, backgroundHandler)

    // Create a camera capture session for camera preview using an ARCore wrapped callback.
    cameraDevice.createCaptureSession(surfaceList, wrappedCallback, backgroundHandler)
  } catch (e: CameraAccessException) {
    Log.e(TAG, "CameraAccessException", e)
  }
}

以非 AR 或 AR 模式启动

如需开始捕获帧,请从相机拍摄会话 onConfigured() 状态回调中调用 captureSession.setRepeatingRequest()。在 onActive() 回调中恢复 ARCore 会话,以 AR 模式启动。

Java

// Repeating camera capture session state callback.
CameraCaptureSession.StateCallback cameraSessionStateCallback =
    new CameraCaptureSession.StateCallback() {

      // Called when ARCore first configures the camera capture session after
      // initializing the app, and again each time the activity resumes.
      @Override
      public void onConfigured(@NonNull CameraCaptureSession session) {
        captureSession = session;
        setRepeatingCaptureRequest();
      }

      @Override
      public void onActive(@NonNull CameraCaptureSession session) {
        if (arMode && !arcoreActive) {
          resumeARCore();
        }
      }
    };

// A repeating camera capture session capture callback.
CameraCaptureSession.CaptureCallback cameraCaptureCallback =
    new CameraCaptureSession.CaptureCallback() {
      @Override
      public void onCaptureCompleted(…) {
        shouldUpdateSurfaceTexture.set(true);
      }
    };

void setRepeatingCaptureRequest() {
    captureSession.setRepeatingRequest(
        previewCaptureRequestBuilder.build(), cameraCaptureCallback, backgroundHandler);
}

void resumeARCore() {
    // Resume ARCore.
    sharedSession.resume();
    arcoreActive = true;

    // Set the capture session callback while in AR mode.
    sharedCamera.setCaptureCallback(cameraCaptureCallback, backgroundHandler);
}

Kotlin

val cameraSessionStateCallback = object : CameraCaptureSession.StateCallback() {
      // Called when ARCore first configures the camera capture session after
      // initializing the app, and again each time the activity resumes.
  override fun onConfigured(session: CameraCaptureSession) {
    captureSession = session
    setRepeatingCaptureRequest()
  }

  override fun onActive(session: CameraCaptureSession) {
    if (arMode && !arcoreActive) {
      resumeARCore()
    }
  }
}

val cameraCaptureCallback = object : CameraCaptureSession.CaptureCallback() {
  override fun onCaptureCompleted(
    session: CameraCaptureSession,
    request: CaptureRequest,
    result: TotalCaptureResult
  ) {
    shouldUpdateSurfaceTexture.set(true);
  }
}

fun setRepeatingCaptureRequest() {
  captureSession.setRepeatingRequest(
    previewCaptureRequestBuilder.build(), cameraCaptureCallback, backgroundHandler
  )
}

fun resumeARCore() {
    // Resume ARCore.
    sharedSession.resume()
    arcoreActive = true

    // Set the capture session callback while in AR mode.
    sharedCamera.setCaptureCallback(cameraCaptureCallback, backgroundHandler)
}

在运行时在非 AR 或 AR 模式之间无缝切换

如需从非 AR 模式切换到 AR 模式并恢复暂停的 ARCore 会话,请执行以下操作:

Java

// Resume the ARCore session.
resumeARCore();

Kotlin

// Resume the ARCore session.
resumeARCore()

如需从 AR 模式切换到非 AR 模式,请执行以下操作:

Java

// Pause ARCore.
sharedSession.pause();

// Create the Camera2 repeating capture request.
setRepeatingCaptureRequest();

Kotlin

// Pause ARCore.
sharedSession.pause()

// Create the Camera2 repeating capture request.
setRepeatingCaptureRequest()