高通 Camera API： Camera.getNumberOfCameras()分析

背景

最近调试的高通设备有前摄后摄扫描头三个camera设备
但是app 使用接口 Camera.getNumberOfCameras()的返回值为2. 出于好奇看了一下接口源码实现

接口实现分析

    /*** Returns the number of physical cameras available on this device.* The return value of this method might change dynamically if the device* supports external cameras and an external camera is connected or* disconnected.** If there is a* {@link android.hardware.camera2.CameraCharacteristics#REQUEST_AVAILABLE_CAPABILITIES_LOGICAL_MULTI_CAMERA* logical multi-camera} in the system, to maintain app backward compatibility, this method will* only expose one camera per facing for all logical camera and physical camera groups.* Use camera2 API to see all cameras.** @return total number of accessible camera devices, or 0 if there are no*   cameras or an error was encountered enumerating them.*/public static int getNumberOfCameras() {boolean exposeAuxCamera = false;String packageName = ActivityThread.currentOpPackageName();/* Force to expose only two cameras* if the package name does not falls in this bucket*/String packageList = SystemProperties.get("vendor.camera.aux.packagelist");if (packageList.length() > 0) {TextUtils.StringSplitter splitter = new TextUtils.SimpleStringSplitter(',');splitter.setString(packageList);for (String str : splitter) {if (packageName.equals(str)) {exposeAuxCamera = true;break;}}}int numberOfCameras = _getNumberOfCameras();if (exposeAuxCamera == false && (numberOfCameras > 2)) {numberOfCameras = 2;}return numberOfCameras;}/*** Returns the number of physical cameras available on this device.*//** @hide */public native static int _getNumberOfCameras();

作为对比 AOSP的代码如下：

    /*** Returns the number of physical cameras available on this device.* The return value of this method might change dynamically if the device* supports external cameras and an external camera is connected or* disconnected.** If there is a* {@link android.hardware.camera2.CameraCharacteristics#REQUEST_AVAILABLE_CAPABILITIES_LOGICAL_MULTI_CAMERA* logical multi-camera} in the system, to maintain app backward compatibility, this method will* only expose one camera per facing for all logical camera and physical camera groups.* Use camera2 API to see all cameras.** @return total number of accessible camera devices, or 0 if there are no*   cameras or an error was encountered enumerating them.*/public native static int getNumberOfCameras();

我们可以看到高通的实现做了一层简单的封装
AOSP中获取物理设备的接口加入了_前缀变为隐藏起开
对app开放的是高通封装后的实现
在这个封装中加入了一个属性 “vendor.camera.aux.packagelist”
只有在这个属性中定义的应用才能获得超过2个的摄像头
默认这个属性只有高通的骁龙相机

#Expose aux camera for below packages
vendor.camera.aux.packagelist=org.codeaurora.snapcam

其他app,当设备camera设备超过3个的时候，只能获得2个的结果

为什么？

拙以为这个接口是针对手机的物理形态适配的一个前摄一个后摄。多余三个的情况多余的情况大概率是后摄的多镜头可以看做一个设备

如何处理？

如果想单独使用扫描头作为物理设备：
可以如下尝试操作来打开

     try {Method openMethod = Class.forName("android.hardware.Camera").getMethod("openLegacy", int.class, int.class);mCamera = (android.hardware.Camera) openMethod.invoke(null, 2, CAMERA_HAL_API_VERSION_1_0);mCamera.setDisplayOrientation(oritationAdjust);} catch (Exception e) {/* Retry with open if openLegacy doesn't exist/fails */Log.v(TAG, "openLegacy failed due to " + e.getMessage()+ ", using open instead");mCamera = android.hardware.Camera.open(2);}

拓展

类似的接口还有
CameraManager.getCameraIdList()

        /*** Get a list of all camera IDs that are at least PRESENT; ignore devices that are* NOT_PRESENT or ENUMERATING, since they cannot be used by anyone.*/public String[] getCameraIdList() {String[] cameraIds = null;synchronized(mLock) {// Try to make sure we have an up-to-date list of camera devices.connectCameraServiceLocked();boolean exposeAuxCamera = false;String packageName = ActivityThread.currentOpPackageName();String packageList = SystemProperties.get("vendor.camera.aux.packagelist");if (packageList.length() > 0) {TextUtils.StringSplitter splitter = new TextUtils.SimpleStringSplitter(',');splitter.setString(packageList);for (String str : splitter) {if (packageName.equals(str)) {exposeAuxCamera = true;break;}}}int idCount = 0;for (int i = 0; i < mDeviceStatus.size(); i++) {if(!exposeAuxCamera && (i == 2)) break;int status = mDeviceStatus.valueAt(i);if (status == ICameraServiceListener.STATUS_NOT_PRESENT ||status == ICameraServiceListener.STATUS_ENUMERATING) continue;idCount++;}cameraIds = new String[idCount];idCount = 0;for (int i = 0; i < mDeviceStatus.size(); i++) {if(!exposeAuxCamera && (i == 2)) break;int status = mDeviceStatus.valueAt(i);if (status == ICameraServiceListener.STATUS_NOT_PRESENT ||status == ICameraServiceListener.STATUS_ENUMERATING) continue;cameraIds[idCount] = mDeviceStatus.keyAt(i);idCount++;}}// The sort logic must match the logic in// libcameraservice/common/CameraProviderManager.cpp::getAPI1CompatibleCameraDeviceIdsArrays.sort(cameraIds, new Comparator<String>() {@Overridepublic int compare(String s1, String s2) {int s1Int = 0, s2Int = 0;try {s1Int = Integer.parseInt(s1);} catch (NumberFormatException e) {s1Int = -1;}try {s2Int = Integer.parseInt(s2);} catch (NumberFormatException e) {s2Int = -1;}// Uint device IDs firstif (s1Int >= 0 && s2Int >= 0) {return s1Int - s2Int;} else if (s1Int >= 0) {return -1;} else if (s2Int >= 0) {return 1;} else {// Simple string compare if both id are not uintreturn s1.compareTo(s2);}}});return cameraIds;}

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Camera API : Camera.getNumberOfCameras()分析

文章目录

高通 Camera API： Camera.getNumberOfCameras()分析

背景

接口实现分析

为什么？

如何处理？

拓展

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