Camera2 openCamera

Camera2 中，CameraManager.java管理所有camera设备，

获取cameraManager：

mCameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);

打开camera：

mCameraManager.openCamera(mCameraId, DeviceStateCallback, mHandler);

打开camera过程：

    public void openCamera(@NonNull String cameraId,
            @NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler)
            throws CameraAccessException {

        if (cameraId == null) {
            throw new IllegalArgumentException("cameraId was null");
        } else if (callback == null) {
            throw new IllegalArgumentException("callback was null");
        } else if (handler == null) {
            if (Looper.myLooper() != null) {
                handler = new Handler();
            } else {
                throw new IllegalArgumentException(
                        "Handler argument is null, but no looper exists in the calling thread");
            }
        }

        openCameraDeviceUserAsync(cameraId, callback, handler);

openCameraDeviceUserAsync:

   private CameraDevice openCameraDeviceUserAsync(String cameraId,
            CameraDevice.StateCallback callback, Handler handler)
            throws CameraAccessException {
        CameraCharacteristics characteristics = getCameraCharacteristics(cameraId);
        CameraDevice device = null;
        try {

            synchronized (mLock) {

                ICameraDeviceUser cameraUser = null;

                android.hardware.camera2.impl.CameraDeviceImpl deviceImpl =
                        new android.hardware.camera2.impl.CameraDeviceImpl(
                                cameraId,
                                callback,
                                handler,
                                characteristics);

                BinderHolder holder = new BinderHolder();

                ICameraDeviceCallbacks callbacks = deviceImpl.getCallbacks();
                int id = Integer.parseInt(cameraId);
                try {
                    if (supportsCamera2ApiLocked(cameraId)) {    //到CameraService.cpp中查询是否支持API2 ，需要HAL支持ModuleApiVersion >= CAMERA_MODULE_API_VERSION_2_0
                        // Use cameraservice's cameradeviceclient implementation for HAL3.2+ devices
                        ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
                        if (cameraService == null) {
                            throw new CameraRuntimeException(
                                CameraAccessException.CAMERA_DISCONNECTED,
                                "Camera service is currently unavailable");
                        }
                        cameraService.connectDevice(callbacks, id,
                                mContext.getOpPackageName(), USE_CALLING_UID, holder);
                        cameraUser = ICameraDeviceUser.Stub.asInterface(holder.getBinder());//API2.0，获取native层Client
                    } else {  //CameraDeviceUserShim 兼容API1.0， 在java层使用camera.java通过JNI与native层通信。

                        // Use legacy camera implementation for HAL1 devices
                        Log.i(TAG, "Using legacy camera HAL.");
                        cameraUser = CameraDeviceUserShim.connectBinderShim(callbacks, id); 
                    }
                } catch (CameraRuntimeException e) {
                    if (e.getReason() == CameraAccessException.CAMERA_DEPRECATED_HAL) {
                        throw new AssertionError("Should've gone down the shim path");
                    } else if (e.getReason() == CameraAccessException.CAMERA_IN_USE ||
                            e.getReason() == CameraAccessException.MAX_CAMERAS_IN_USE ||
                            e.getReason() == CameraAccessException.CAMERA_DISABLED ||
                            e.getReason() == CameraAccessException.CAMERA_DISCONNECTED ||
                            e.getReason() == CameraAccessException.CAMERA_ERROR) {
                        // Received one of the known connection errors
                        // The remote camera device cannot be connected to, so
                        // set the local camera to the startup error state
                        deviceImpl.setRemoteFailure(e);

                        if (e.getReason() == CameraAccessException.CAMERA_DISABLED ||
                                e.getReason() == CameraAccessException.CAMERA_DISCONNECTED ||
                                e.getReason() == CameraAccessException.CAMERA_IN_USE) {
                            // Per API docs, these failures call onError and throw
                            throw e.asChecked();
                        }
                    } else {
                        // Unexpected failure - rethrow
                        throw e;
                    }
                } catch (RemoteException e) {
                    // Camera service died - act as if it's a CAMERA_DISCONNECTED case
                    CameraRuntimeException ce = new CameraRuntimeException(
                        CameraAccessException.CAMERA_DISCONNECTED,
                        "Camera service is currently unavailable", e);
                    deviceImpl.setRemoteFailure(ce);
                    throw ce.asChecked();
                }

                // TODO: factor out callback to be non-nested, then move setter to constructor
                // For now, calling setRemoteDevice will fire initial
                // onOpened/onUnconfigured callbacks.
                deviceImpl.setRemoteDevice(cameraUser);
                device = deviceImpl;
            }

        } catch (NumberFormatException e) {
            throw new IllegalArgumentException("Expected cameraId to be numeric, but it was: "
                    + cameraId);
        } catch (CameraRuntimeException e) {
            throw e.asChecked();
        }
        return device;
    }

API1.0通过camera.java---->JNI----->cameraclient。

API2.0通过java层获取到底层CameraClient，使用binder与service通信。