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• CameraX
• Camera2
• Camera（已废弃）

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CameraX 示例应用

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0. CameraX 概览 | Android Jetpack 的一部分

• CameraX 架构
• 配置选项
• 实现预览
• 图片分析
• 图片拍摄
• 视频拍摄
• 供应商扩展
• 转换输出
• 用例旋转
• 实验室测试设备

1. CameraX获取Context.CAMERA_SERVICE服务

CameraXBasic 的setUpCamera()方法第一次调用 ProcessCameraProvider.getInstance() 期间，初始化 CameraX 会cameraFactory.getAvailableCameraIds()枚举和查询设备上可用摄像头的特性。


其中cameraFactory在com/android/example/cameraxbasic/MainApplication.kt中调用CameraXConfig.Builder.fromConfig(Camera2Config.defaultConfig())初始化对象Camera2CameraFactory、CameraXConfig

1.1 获取Context.CAMERA_SERVICE服务

下面获取Context.CAMERA_SERVICE服务，实际获取 SystemServiceRegistry.java中注册的CameraManager.java。通过CameraManagerGlobal连接CameraService

androidx/camera/camera2/internal/Camera2CameraFactory.java
androidx/camera/camera2/internal/compat/CameraManagerCompat.java
androidx/camera/camera2/internal/compat/CameraManagerCompatApi29Impl.java
androidx/camera/camera2/internal/compat/CameraManagerCompatApi28Impl.java
androidx/camera/camera2/internal/compat/CameraManagerCompatBaseImpl.java

frameworks/base/core/java/android/app/SystemServiceRegistry.java

frameworks/base/core/java/android/hardware/camera2/CameraManager.java

public ICameraService getCameraService() {
    synchronized(mLock) {
        connectCameraServiceLocked();
        if (mCameraService == null && !sCameraServiceDisabled) {
            Log.e(TAG, "Camera service is unavailable");
        }
        return mCameraService;
    }
}

private void connectCameraServiceLocked() {
    // Only reconnect if necessary
    if (mCameraService != null || sCameraServiceDisabled) return;

    Log.i(TAG, "Connecting to camera service");

    IBinder cameraServiceBinder = ServiceManager.getService(CAMERA_SERVICE_BINDER_NAME);
    if (cameraServiceBinder == null) {
        // Camera service is now down, leave mCameraService as null
        return;
    }
    try {
        cameraServiceBinder.linkToDeath(this, /*flags*/ 0);
    } catch (RemoteException e) {
        // Camera service is now down, leave mCameraService as null
        return;
    }

    ICameraService cameraService = ICameraService.Stub.asInterface(cameraServiceBinder);

    try {
        CameraMetadataNative.setupGlobalVendorTagDescriptor();
    } catch (ServiceSpecificException e) {
        handleRecoverableSetupErrors(e);
    }

    try {
        CameraStatus[] cameraStatuses = cameraService.addListener(this);
        for (CameraStatus c : cameraStatuses) {
            onStatusChangedLocked(c.status, c.cameraId);

            if (c.unavailablePhysicalCameras != null) {
                for (String unavailPhysicalCamera : c.unavailablePhysicalCameras) {
                    onPhysicalCameraStatusChangedLocked(
                            ICameraServiceListener.STATUS_NOT_PRESENT,
                            c.cameraId, unavailPhysicalCamera);
                }
            }
        }
        mCameraService = cameraService;
    } catch(ServiceSpecificException e) {
        // Unexpected failure
        throw new IllegalStateException("Failed to register a camera service listener", e);
    } catch (RemoteException e) {
        // Camera service is now down, leave mCameraService as null
    }

    try {
        ConcurrentCameraIdCombination[] cameraIdCombinations =
                cameraService.getConcurrentCameraIds();
        for (ConcurrentCameraIdCombination comb : cameraIdCombinations) {
            mConcurrentCameraIdCombinations.add(comb.getConcurrentCameraIdCombination());
        }
    } catch (ServiceSpecificException e) {
        // Unexpected failure
        throw new IllegalStateException("Failed to get concurrent camera id combinations",
                e);
    } catch (RemoteException e) {
        // Camera service died in all probability
    }
}
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1.2 枚举和查询设备上可用摄像头

CameraX 初始化时 cameraFactory.getAvailableCameraIds()枚举和查询设备上可用摄像头的特性。最终调用CameraSelectionOptimizer.getSelectedAvailableCameraIds(this, availableCamerasSelector)通过cameraFactory.getCameraManager().getCameraIdList()获取。


FWK层中CameraManager.java中CameraManagerGlobal的getCameraIdList():connectCameraServiceLocked()连接CameraService服务CAMERA_SERVICE_BINDER_NAME = "media.camera"



摄像头限制器 如果传递给 CameraXConfig.Builder.setAvailableCamerasLimiter() 的 CameraSelector 过滤掉了某个摄像头，则 CameraX 在运行时会假定该摄像头不存在。CameraSelector.DEFAULT_BACK_CAMERA 后置摄像头LENS_FACING_BACK = 1；CameraSelector.DEFAULT_FRONT_CAMERA 前置摄像头LENS_FACING_FRONT = 0。

com/android/example/cameraxbasic/fragments/CameraFragment.kt
androidx/camera/core/CameraX.java
androidx/camera/core/impl/CameraRepository.java

public void init(@NonNull CameraFactory cameraFactory) throws InitializationException {
    synchronized (mCamerasLock) {
        try {
            Set<String> camerasList = cameraFactory.getAvailableCameraIds();
            for (String id : camerasList) {
                Logger.d(TAG, "Added camera: " + id);
                mCameras.put(id, cameraFactory.getCamera(id));
            }
        } catch (CameraUnavailableException e) {
            throw new InitializationException(e);
        }
    }
}
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androidx/camera/camera2/internal/Camera2CameraFactory.java

public Camera2CameraFactory(@NonNull Context context,
        @NonNull CameraThreadConfig threadConfig,
        @Nullable CameraSelector availableCamerasSelector) throws InitializationException {
    mThreadConfig = threadConfig;
    mCameraStateRegistry = new CameraStateRegistry(DEFAULT_ALLOWED_CONCURRENT_OPEN_CAMERAS);
    mCameraManager = CameraManagerCompat.from(context, mThreadConfig.getSchedulerHandler());

    List<String> optimizedCameraIds = CameraSelectionOptimizer.getSelectedAvailableCameraIds(
            this, availableCamerasSelector);
    mAvailableCameraIds = getBackwardCompatibleCameraIds(optimizedCameraIds);
}

public Set<String> getAvailableCameraIds() {
    // Use a LinkedHashSet to preserve order
    return new LinkedHashSet<>(mAvailableCameraIds);
}
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androidx/camera/camera2/internal/CameraSelectionOptimizer.java

static List<String> getSelectedAvailableCameraIds(
        @NonNull Camera2CameraFactory cameraFactory,
        @Nullable CameraSelector availableCamerasSelector)
        throws InitializationException {
    try {
        List<String> availableCameraIds = new ArrayList<>();
        List<String> cameraIdList =
                Arrays.asList(cameraFactory.getCameraManager().getCameraIdList());
        if (availableCamerasSelector == null) {
            for (String id : cameraIdList) {
                availableCameraIds.add(id);
            }
            return availableCameraIds;
        }

        // Skip camera ID by heuristic: 0 is back lens facing, 1 is front lens facing.
        String skippedCameraId;
        try {
            Integer lensFacingInteger = availableCamerasSelector.getLensFacing();
            skippedCameraId = decideSkippedCameraIdByHeuristic(
                    cameraFactory.getCameraManager(), lensFacingInteger, cameraIdList);
        } catch (IllegalStateException e) {
            // Don't skip camera if there is any conflict in camera lens facing.
            skippedCameraId = null;
        }

        List<CameraInfo> cameraInfos = new ArrayList<>();

        for (String id : cameraIdList) {
            if (id.equals(skippedCameraId)) {
                continue;
            }
            Camera2CameraInfoImpl cameraInfo = cameraFactory.getCameraInfo(id);
            cameraInfos.add(cameraInfo);
        }

        List<CameraInfo> filteredCameraInfos =
                availableCamerasSelector.filter(cameraInfos);

        for (CameraInfo cameraInfo : filteredCameraInfos) {
            String cameraId = ((CameraInfoInternal) cameraInfo).getCameraId();
            availableCameraIds.add(cameraId);
        }

        return availableCameraIds;
    } catch (CameraAccessExceptionCompat e) {
        throw new InitializationException(CameraUnavailableExceptionHelper.createFrom(e));
    } catch (CameraUnavailableException e) {
        throw new InitializationException(e);
    }
}
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2. 拍照按钮执行

除了setUpCamera()初始化CameraX，其中重要查看updateCameraUi()布局更新；camera_capture_button按钮cameraUiContainerBinding?.cameraCaptureButton?.setOnClickListener设置
com/android/example/cameraxbasic/fragments/CameraFragment.kt

// Listener for button used to capture photo
cameraUiContainerBinding?.cameraCaptureButton?.setOnClickListener {

    // Get a stable reference of the modifiable image capture use case
    imageCapture?.let { imageCapture ->

        // Create output file to hold the image
        val photoFile = createFile(outputDirectory, FILENAME, PHOTO_EXTENSION)

        // Setup image capture metadata
        val metadata = Metadata().apply {

            // Mirror image when using the front camera
            isReversedHorizontal = lensFacing == CameraSelector.LENS_FACING_FRONT
        }

        // Create output options object which contains file + metadata
        val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile)
                .setMetadata(metadata)
                .build()

        // Setup image capture listener which is triggered after photo has been taken
        imageCapture.takePicture(
                outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
            override fun onError(exc: ImageCaptureException) {
                Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
            }

            override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                val savedUri = output.savedUri ?: Uri.fromFile(photoFile)
                Log.d(TAG, "Photo capture succeeded: $savedUri")

                // We can only change the foreground Drawable using API level 23+ API
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    // Update the gallery thumbnail with latest picture taken
                    setGalleryThumbnail(savedUri)
                }

                // Implicit broadcasts will be ignored for devices running API level >= 24
                // so if you only target API level 24+ you can remove this statement
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
                    requireActivity().sendBroadcast(
                            Intent(android.hardware.Camera.ACTION_NEW_PICTURE, savedUri)
                    )
                }

                // If the folder selected is an external media directory, this is
                // unnecessary but otherwise other apps will not be able to access our
                // images unless we scan them using [MediaScannerConnection]
                val mimeType = MimeTypeMap.getSingleton()
                        .getMimeTypeFromExtension(savedUri.toFile().extension)
                MediaScannerConnection.scanFile(
                        context,
                        arrayOf(savedUri.toFile().absolutePath),
                        arrayOf(mimeType)
                ) { _, uri ->
                    Log.d(TAG, "Image capture scanned into media store: $uri")
                }
            }
        })

        // We can only change the foreground Drawable using API level 23+ API
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

            // Display flash animation to indicate that photo was captured
            fragmentCameraBinding.root.postDelayed({
                fragmentCameraBinding.root.foreground = ColorDrawable(Color.WHITE)
                fragmentCameraBinding.root.postDelayed(
                        { fragmentCameraBinding.root.foreground = null }, ANIMATION_FAST_MILLIS)
            }, ANIMATION_SLOW_MILLIS)
        }
    }
}
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3. 前置/后置 摄像头切换

查看updateCameraUi()布局更新；camera_switch_button按钮cameraUiContainerBinding?.cameraSwitchButton?.let设置，CameraSelector.LENS_FACING_BACK、CameraSelector.LENS_FACING_FRONT 前后置属性，bindCameraUseCases()更新预览preview、捕获imageCapture和分析imageAnalyzer用例；observeCameraState(camera?.cameraInfo!!)监听Camera状态


com/android/example/cameraxbasic/fragments/CameraFragment.kt

// Setup for button used to switch cameras
cameraUiContainerBinding?.cameraSwitchButton?.let {

    // Disable the button until the camera is set up
    it.isEnabled = false

    // Listener for button used to switch cameras. Only called if the button is enabled
    it.setOnClickListener {
        lensFacing = if (CameraSelector.LENS_FACING_FRONT == lensFacing) {
            CameraSelector.LENS_FACING_BACK
        } else {
            CameraSelector.LENS_FACING_FRONT
        }
        // Re-bind use cases to update selected camera
        bindCameraUseCases()
    }
}

/** Declare and bind preview, capture and analysis use cases */
private fun bindCameraUseCases() {

    // Get screen metrics used to setup camera for full screen resolution
    val metrics = windowManager.getCurrentWindowMetrics().bounds
    Log.d(TAG, "Screen metrics: ${metrics.width()} x ${metrics.height()}")

    val screenAspectRatio = aspectRatio(metrics.width(), metrics.height())
    Log.d(TAG, "Preview aspect ratio: $screenAspectRatio")

    val rotation = fragmentCameraBinding.viewFinder.display.rotation

    // CameraProvider
    val cameraProvider = cameraProvider
            ?: throw IllegalStateException("Camera initialization failed.")

    // CameraSelector
    val cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()

    // Preview
    preview = Preview.Builder()
            // We request aspect ratio but no resolution
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation
            .setTargetRotation(rotation)
            .build()

    // ImageCapture
    imageCapture = ImageCapture.Builder()
            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
            // We request aspect ratio but no resolution to match preview config, but letting
            // CameraX optimize for whatever specific resolution best fits our use cases
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation, we will have to call this again if rotation changes
            // during the lifecycle of this use case
            .setTargetRotation(rotation)
            .build()

    // ImageAnalysis
    imageAnalyzer = ImageAnalysis.Builder()
            // We request aspect ratio but no resolution
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation, we will have to call this again if rotation changes
            // during the lifecycle of this use case
            .setTargetRotation(rotation)
            .build()
            // The analyzer can then be assigned to the instance
            .also {
                it.setAnalyzer(cameraExecutor, LuminosityAnalyzer { luma ->
                    // Values returned from our analyzer are passed to the attached listener
                    // We log image analysis results here - you should do something useful
                    // instead!
                    Log.d(TAG, "Average luminosity: $luma")
                })
            }

    // Must unbind the use-cases before rebinding them
    cameraProvider.unbindAll()

    try {
        // A variable number of use-cases can be passed here -
        // camera provides access to CameraControl & CameraInfo
        camera = cameraProvider.bindToLifecycle(
                this, cameraSelector, preview, imageCapture, imageAnalyzer)

        // Attach the viewfinder's surface provider to preview use case
        preview?.setSurfaceProvider(fragmentCameraBinding.viewFinder.surfaceProvider)
        observeCameraState(camera?.cameraInfo!!)
    } catch (exc: Exception) {
        Log.e(TAG, "Use case binding failed", exc)
    }
}
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