android camera: android.hardware.camera2向下和camera service

android.hardware.camera2向下和camera service的通信是通过mCameraService和mRemoteDevice

frameworks/base/core/java/android/hardware/camera2/
/**
* A per-process global camera manager instance, to retain a connection to the camera service,
* and to distribute camera availability notices to API-registered callbacks
*/
private static final class CameraManagerGlobal extends ICameraServiceListener.Stub
        /**
         * Connect to the camera service if it's available, and set up listeners.
         */
private static final String CAMERA_SERVICE_BINDER_NAME = "media.camera";
        private void connectCameraServiceLocked() {
            IBinder cameraServiceBinder = ServiceManager.getService(CAMERA_SERVICE_BINDER_NAME);

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

            CameraMetadataNative.setupGlobalVendorTagDescriptor();


            try {
                CameraStatus[] cameraStatuses = cameraService.addListener(this);
                for (CameraStatus c : cameraStatuses) {
                    onStatusChangedLocked(c.status, c.cameraId);
                }
                mCameraService = cameraService;
            }
        }
}
通过JNI调用setupGlobalVendorTagDescriptor，natice层也是调用CameraService做具体的实现。


CameraManager通过CameraMangerGlobal工作：
public void openCamera(@NonNull String cameraId,
            @NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler)　->
public void openCameraForUid(@NonNull String cameraId,
    @NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler,
    int clientUid) ->
private CameraDevice openCameraDeviceUserAsync(String cameraId,
    CameraDevice.StateCallback callback, Handler handler, final int uid){
        CameraCharacteristics characteristics = getCameraCharacteristics(cameraId);
        CameraDevice device = null;


   ICameraDeviceUser cameraUser = null;
   android.hardware.camera2.impl.CameraDeviceImpl deviceImpl =
   new android.hardware.camera2.impl.CameraDeviceImpl(
       cameraId,
       callback,
       handler,
       characteristics,
       mContext.getApplicationInfo().targetSdkVersion);
            ICameraDeviceCallbacks callbacks = deviceImpl.getCallbacks();
   // Use cameraservice's cameradeviceclient implementation for HAL3.2+ devices
            ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
            cameraUser = cameraService.connectDevice(callbacks, cameraId,
                    mContext.getOpPackageName(), uid);
            deviceImpl.setRemoteDevice(cameraUser);
            device = deviceImpl;
        return device;
}

CameraDevice, CameraDeviceImpl, ICameraDeviceUser三者之间的关系：
public class CameraDeviceImpl extends CameraDevice
public void setRemoteDevice(ICameraDeviceUser remoteDevice) throws CameraAccessException {
    mRemoteDevice = new ICameraDeviceUserWrapper(remoteDevice);
    mDeviceHandler.post(mCallOnOpened);
    mDeviceHandler.post(mCallOnUnconfigured);
}

1. 通过ICameraService接口访问ICameraService.aidl

ICameraService cameraService = CameraManagerGlobal.get().getCameraService();

ICameraDeviceUser cameraUser=

cameraService . connectDevice ( callbacks , cameraId , mContext . getOpPackageName (), uid );

mRemoteDevice = new ICameraDeviceUserWrapper(cameraUser);

2. 通过ICameraDeviceUserWrapper mRemoteDevice访问ICameraDeviceUser.aidl

这里Wrapper的意思只是多了异常捕捉而已

    public void prepare(int streamId) throws CameraAccessException {
        try {
            mRemoteDevice.prepare(streamId);
        } catch (Throwable t) {
            CameraManager.throwAsPublicException(t);
            throw new UnsupportedOperationException("Unexpected exception", t);
        }
    }