android/android-9.0.0_r35 : android/hardware/camera2/CameraManager.java

CameraManager
https://source.android.com/
/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.hardware.camera2;

import android.annotation.CallbackExecutor;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.RequiresPermission;
import android.annotation.SystemService;
import android.content.Context;
import android.hardware.CameraInfo;
import android.hardware.CameraStatus;
import android.hardware.ICameraService;
import android.hardware.ICameraServiceListener;
import android.hardware.camera2.impl.CameraDeviceImpl;
import android.hardware.camera2.impl.CameraMetadataNative;
import android.hardware.camera2.legacy.CameraDeviceUserShim;
import android.hardware.camera2.legacy.LegacyMetadataMapper;
import android.os.Binder;
import android.os.DeadObjectException;
import android.os.Handler;
import android.os.IBinder;
import android.os.Looper;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.os.ServiceSpecificException;
import android.os.SystemProperties;
import android.util.ArrayMap;
import android.util.Log;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

A system service manager for detecting, characterizing, and connecting to CameraDevices.
For more details about communicating with camera devices, read the Camera developer guide or the camera2 package documentation.
/**
 * <p>A system service manager for detecting, characterizing, and connecting to
 * {@link CameraDevice CameraDevices}.</p>
 *
 * <p>For more details about communicating with camera devices, read the Camera
 * developer guide or the {@link android.hardware.camera2 camera2}
 * package documentation.</p>
 */
@SystemService(Context.CAMERA_SERVICE)
public final class CameraManager {

    private static final String TAG = "CameraManager";
    private final boolean DEBUG = false;

    private static final int USE_CALLING_UID = -1;

    @SuppressWarnings("unused")
    private static final int API_VERSION_1 = 1;
    private static final int API_VERSION_2 = 2;

    private static final int CAMERA_TYPE_BACKWARD_COMPATIBLE = 0;
    private static final int CAMERA_TYPE_ALL = 1;

    private ArrayList<String> mDeviceIdList;

    private final Context mContext;
    private final Object mLock = new Object();

    @hide /**
     * @hide
     */
    public CameraManager(Context context) {
        synchronized(mLock) {
            mContext = context;
        }
    }

    Return the list of currently connected camera devices by identifier, including
cameras that may be in use by other camera API clients.
Non-removable cameras use integers starting at 0 for their
identifiers, while removable cameras have a unique identifier for each
individual device, even if they are the same model.
Returns: The list of currently connected camera devices./**
     * Return the list of currently connected camera devices by identifier, including
     * cameras that may be in use by other camera API clients.
     *
     * <p>Non-removable cameras use integers starting at 0 for their
     * identifiers, while removable cameras have a unique identifier for each
     * individual device, even if they are the same model.</p>
     *
     * @return The list of currently connected camera devices.
     */
    @NonNull
    public String[] getCameraIdList() throws CameraAccessException {
        return CameraManagerGlobal.get().getCameraIdList();
    }

    Register a callback to be notified about camera device availability.
Registering the same callback again will replace the handler with the
new one provided.
The first time a callback is registered, it is immediately called
with the availability status of all currently known camera devices.
AvailabilityCallback.onCameraUnavailable(String) will be called whenever a camera device is opened by any camera API client. As of API level 23, other camera API clients may still be able to open such a camera device, evicting the existing client if they have higher priority than the existing client of a camera device. See open() for more details.
Since this callback will be registered with the camera service, remember to unregister it
once it is no longer needed; otherwise the callback will continue to receive events
indefinitely and it may prevent other resources from being released. Specifically, the
callbacks will be invoked independently of the general activity lifecycle and independently
of the state of individual CameraManager instances.
Params: callback – the new callback to send camera availability notices to
handler – The handler on which the callback should be invoked, or null to use the current thread's looper.
Throws: IllegalArgumentException – if the handler is null but the current thread has no looper./**
     * Register a callback to be notified about camera device availability.
     *
     * <p>Registering the same callback again will replace the handler with the
     * new one provided.</p>
     *
     * <p>The first time a callback is registered, it is immediately called
     * with the availability status of all currently known camera devices.</p>
     *
     * <p>{@link AvailabilityCallback#onCameraUnavailable(String)} will be called whenever a camera
     * device is opened by any camera API client. As of API level 23, other camera API clients may
     * still be able to open such a camera device, evicting the existing client if they have higher
     * priority than the existing client of a camera device. See open() for more details.</p>
     *
     * <p>Since this callback will be registered with the camera service, remember to unregister it
     * once it is no longer needed; otherwise the callback will continue to receive events
     * indefinitely and it may prevent other resources from being released. Specifically, the
     * callbacks will be invoked independently of the general activity lifecycle and independently
     * of the state of individual CameraManager instances.</p>
     *
     * @param callback the new callback to send camera availability notices to
     * @param handler The handler on which the callback should be invoked, or {@code null} to use
     *             the current thread's {@link android.os.Looper looper}.
     *
     * @throws IllegalArgumentException if the handler is {@code null} but the current thread has
     *             no looper.
     */
    public void registerAvailabilityCallback(@NonNull AvailabilityCallback callback,
            @Nullable Handler handler) {
        CameraManagerGlobal.get().registerAvailabilityCallback(callback,
                CameraDeviceImpl.checkAndWrapHandler(handler));
    }

    Register a callback to be notified about camera device availability.
The behavior of this method matches that of registerAvailabilityCallback(AvailabilityCallback, Handler), except that it uses Executor as an argument instead of Handler.
Params: executor – The executor which will be used to invoke the callback.
callback – the new callback to send camera availability notices to
Throws: IllegalArgumentException – if the executor is null./**
     * Register a callback to be notified about camera device availability.
     *
     * <p>The behavior of this method matches that of
     * {@link #registerAvailabilityCallback(AvailabilityCallback, Handler)},
     * except that it uses {@link java.util.concurrent.Executor} as an argument
     * instead of {@link android.os.Handler}.</p>
     *
     * @param executor The executor which will be used to invoke the callback.
     * @param callback the new callback to send camera availability notices to
     *
     * @throws IllegalArgumentException if the executor is {@code null}.
     */
    public void registerAvailabilityCallback(@NonNull @CallbackExecutor Executor executor,
            @NonNull AvailabilityCallback callback) {
        if (executor == null) {
            throw new IllegalArgumentException("executor was null");
        }
        CameraManagerGlobal.get().registerAvailabilityCallback(callback, executor);
    }

    Remove a previously-added callback; the callback will no longer receive connection and
disconnection callbacks.
Removing a callback that isn't registered has no effect.
Params: callback – The callback to remove from the notification list/**
     * Remove a previously-added callback; the callback will no longer receive connection and
     * disconnection callbacks.
     *
     * <p>Removing a callback that isn't registered has no effect.</p>
     *
     * @param callback The callback to remove from the notification list
     */
    public void unregisterAvailabilityCallback(@NonNull AvailabilityCallback callback) {
        CameraManagerGlobal.get().unregisterAvailabilityCallback(callback);
    }

    Register a callback to be notified about torch mode status.
Registering the same callback again will replace the handler with the
new one provided.
The first time a callback is registered, it is immediately called
with the torch mode status of all currently known camera devices with a flash unit.
Since this callback will be registered with the camera service, remember to unregister it
once it is no longer needed; otherwise the callback will continue to receive events
indefinitely and it may prevent other resources from being released. Specifically, the
callbacks will be invoked independently of the general activity lifecycle and independently
of the state of individual CameraManager instances.
Params: callback – The new callback to send torch mode status to
handler – The handler on which the callback should be invoked, or null to use the current thread's looper.
Throws: IllegalArgumentException – if the handler is null but the current thread has no looper./**
     * Register a callback to be notified about torch mode status.
     *
     * <p>Registering the same callback again will replace the handler with the
     * new one provided.</p>
     *
     * <p>The first time a callback is registered, it is immediately called
     * with the torch mode status of all currently known camera devices with a flash unit.</p>
     *
     * <p>Since this callback will be registered with the camera service, remember to unregister it
     * once it is no longer needed; otherwise the callback will continue to receive events
     * indefinitely and it may prevent other resources from being released. Specifically, the
     * callbacks will be invoked independently of the general activity lifecycle and independently
     * of the state of individual CameraManager instances.</p>
     *
     * @param callback The new callback to send torch mode status to
     * @param handler The handler on which the callback should be invoked, or {@code null} to use
     *             the current thread's {@link android.os.Looper looper}.
     *
     * @throws IllegalArgumentException if the handler is {@code null} but the current thread has
     *             no looper.
     */
    public void registerTorchCallback(@NonNull TorchCallback callback, @Nullable Handler handler) {
        CameraManagerGlobal.get().registerTorchCallback(callback,
                CameraDeviceImpl.checkAndWrapHandler(handler));
    }

    Register a callback to be notified about torch mode status.
The behavior of this method matches that of registerTorchCallback(TorchCallback, Handler), except that it uses Executor as an argument instead of Handler.
Params: executor – The executor which will be used to invoke the callback
callback – The new callback to send torch mode status to
Throws: IllegalArgumentException – if the executor is null./**
     * Register a callback to be notified about torch mode status.
     *
     * <p>The behavior of this method matches that of
     * {@link #registerTorchCallback(TorchCallback, Handler)},
     * except that it uses {@link java.util.concurrent.Executor} as an argument
     * instead of {@link android.os.Handler}.</p>
     *
     * @param executor The executor which will be used to invoke the callback
     * @param callback The new callback to send torch mode status to
     *
     * @throws IllegalArgumentException if the executor is {@code null}.
     */
    public void registerTorchCallback(@NonNull @CallbackExecutor Executor executor,
            @NonNull TorchCallback callback) {
        if (executor == null) {
            throw new IllegalArgumentException("executor was null");
        }
        CameraManagerGlobal.get().registerTorchCallback(callback, executor);
    }

    Remove a previously-added callback; the callback will no longer receive torch mode status
callbacks.
Removing a callback that isn't registered has no effect.
Params: callback – The callback to remove from the notification list/**
     * Remove a previously-added callback; the callback will no longer receive torch mode status
     * callbacks.
     *
     * <p>Removing a callback that isn't registered has no effect.</p>
     *
     * @param callback The callback to remove from the notification list
     */
    public void unregisterTorchCallback(@NonNull TorchCallback callback) {
        CameraManagerGlobal.get().unregisterTorchCallback(callback);
    }

    Query the capabilities of a camera device. These capabilities are
immutable for a given camera.
Params: cameraId – The id of the camera device to query
Throws: IllegalArgumentException – if the cameraId does not match any
        known camera device.
CameraAccessException – if the camera device has been disconnected.
See Also: getCameraIdList
DevicePolicyManager.setCameraDisabled
Returns: The properties of the given camera/**
     * <p>Query the capabilities of a camera device. These capabilities are
     * immutable for a given camera.</p>
     *
     * @param cameraId The id of the camera device to query
     * @return The properties of the given camera
     *
     * @throws IllegalArgumentException if the cameraId does not match any
     *         known camera device.
     * @throws CameraAccessException if the camera device has been disconnected.
     *
     * @see #getCameraIdList
     * @see android.app.admin.DevicePolicyManager#setCameraDisabled
     */
    @NonNull
    public CameraCharacteristics getCameraCharacteristics(@NonNull String cameraId)
            throws CameraAccessException {
        CameraCharacteristics characteristics = null;
        if (CameraManagerGlobal.sCameraServiceDisabled) {
            throw new IllegalArgumentException("No cameras available on device");
        }
        synchronized (mLock) {
            /*
             * Get the camera characteristics from the camera service directly if it supports it,
             * otherwise get them from the legacy shim instead.
             */
            ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
            if (cameraService == null) {
                throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
                        "Camera service is currently unavailable");
            }
            try {
                if (!supportsCamera2ApiLocked(cameraId)) {
                    // Legacy backwards compatibility path; build static info from the camera
                    // parameters
                    int id = Integer.parseInt(cameraId);

                    String parameters = cameraService.getLegacyParameters(id);

                    CameraInfo info = cameraService.getCameraInfo(id);

                    characteristics = LegacyMetadataMapper.createCharacteristics(parameters, info);
                } else {
                    // Normal path: Get the camera characteristics directly from the camera service
                    CameraMetadataNative info = cameraService.getCameraCharacteristics(cameraId);

                    characteristics = new CameraCharacteristics(info);
                }
            } catch (ServiceSpecificException e) {
                throwAsPublicException(e);
            } catch (RemoteException e) {
                // Camera service died - act as if the camera was disconnected
                throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
                        "Camera service is currently unavailable", e);
            }
        }
        return characteristics;
    }

    Helper for opening a connection to a camera with the given ID.
Params: cameraId – The unique identifier of the camera device to open
callback – The callback for the camera. Must not be null.
executor – The executor to invoke the callback with. Must not be null.
uid –      The UID of the application actually opening the camera.
                Must be USE_CALLING_UID unless the caller is a service
                that is trusted to open the device on behalf of an
                application and to forward the real UID.
Throws: CameraAccessException – if the camera is disabled by device policy,
too many camera devices are already open, or the cameraId does not match
any currently available camera device.
SecurityException – if the application does not have permission to
access the camera
IllegalArgumentException – if callback or handler is null.
See Also: getCameraIdList
DevicePolicyManager.setCameraDisabled
Returns: A handle to the newly-created camera device./**
     * Helper for opening a connection to a camera with the given ID.
     *
     * @param cameraId The unique identifier of the camera device to open
     * @param callback The callback for the camera. Must not be null.
     * @param executor The executor to invoke the callback with. Must not be null.
     * @param uid      The UID of the application actually opening the camera.
     *                 Must be USE_CALLING_UID unless the caller is a service
     *                 that is trusted to open the device on behalf of an
     *                 application and to forward the real UID.
     *
     * @throws CameraAccessException if the camera is disabled by device policy,
     * too many camera devices are already open, or the cameraId does not match
     * any currently available camera device.
     *
     * @throws SecurityException if the application does not have permission to
     * access the camera
     * @throws IllegalArgumentException if callback or handler is null.
     * @return A handle to the newly-created camera device.
     *
     * @see #getCameraIdList
     * @see android.app.admin.DevicePolicyManager#setCameraDisabled
     */
    private CameraDevice openCameraDeviceUserAsync(String cameraId,
            CameraDevice.StateCallback callback, Executor executor, final int uid)
            throws CameraAccessException {
        CameraCharacteristics characteristics = getCameraCharacteristics(cameraId);
        CameraDevice device = null;

        synchronized (mLock) {

            ICameraDeviceUser cameraUser = null;

            android.hardware.camera2.impl.CameraDeviceImpl deviceImpl =
                    new android.hardware.camera2.impl.CameraDeviceImpl(
                        cameraId,
                        callback,
                        executor,
                        characteristics,
                        mContext.getApplicationInfo().targetSdkVersion);

            ICameraDeviceCallbacks callbacks = deviceImpl.getCallbacks();

            try {
                if (supportsCamera2ApiLocked(cameraId)) {
                    // Use cameraservice's cameradeviceclient implementation for HAL3.2+ devices
                    ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
                    if (cameraService == null) {
                        throw new ServiceSpecificException(
                            ICameraService.ERROR_DISCONNECTED,
                            "Camera service is currently unavailable");
                    }
                    cameraUser = cameraService.connectDevice(callbacks, cameraId,
                            mContext.getOpPackageName(), uid);
                } else {
                    // Use legacy camera implementation for HAL1 devices
                    int id;
                    try {
                        id = Integer.parseInt(cameraId);
                    } catch (NumberFormatException e) {
                        throw new IllegalArgumentException("Expected cameraId to be numeric, but it was: "
                                + cameraId);
                    }

                    Log.i(TAG, "Using legacy camera HAL.");
                    cameraUser = CameraDeviceUserShim.connectBinderShim(callbacks, id);
                }
            } catch (ServiceSpecificException e) {
                if (e.errorCode == ICameraService.ERROR_DEPRECATED_HAL) {
                    throw new AssertionError("Should've gone down the shim path");
                } else if (e.errorCode == ICameraService.ERROR_CAMERA_IN_USE ||
                        e.errorCode == ICameraService.ERROR_MAX_CAMERAS_IN_USE ||
                        e.errorCode == ICameraService.ERROR_DISABLED ||
                        e.errorCode == ICameraService.ERROR_DISCONNECTED ||
                        e.errorCode == ICameraService.ERROR_INVALID_OPERATION) {
                    // 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.errorCode == ICameraService.ERROR_DISABLED ||
                            e.errorCode == ICameraService.ERROR_DISCONNECTED ||
                            e.errorCode == ICameraService.ERROR_CAMERA_IN_USE) {
                        // Per API docs, these failures call onError and throw
                        throwAsPublicException(e);
                    }
                } else {
                    // Unexpected failure - rethrow
                    throwAsPublicException(e);
                }
            } catch (RemoteException e) {
                // Camera service died - act as if it's a CAMERA_DISCONNECTED case
                ServiceSpecificException sse = new ServiceSpecificException(
                    ICameraService.ERROR_DISCONNECTED,
                    "Camera service is currently unavailable");
                deviceImpl.setRemoteFailure(sse);
                throwAsPublicException(sse);
            }

            // TODO: factor out callback to be non-nested, then move setter to constructor
            // For now, calling setRemoteDevice will fire initial
            // onOpened/onUnconfigured callbacks.
            // This function call may post onDisconnected and throw CAMERA_DISCONNECTED if
            // cameraUser dies during setup.
            deviceImpl.setRemoteDevice(cameraUser);
            device = deviceImpl;
        }

        return device;
    }

    Open a connection to a camera with the given ID.
Use getCameraIdList to get the list of available camera devices. Note that even if an id is listed, open may fail if the device is disconnected between the calls to getCameraIdList and openCamera, or if a higher-priority camera API client begins using the camera device.
As of API level 23, devices for which the AvailabilityCallback.onCameraUnavailable(String) callback has been called due to the device being in use by a lower-priority, background camera API client can still potentially be opened by calling this method when the calling camera API client has a higher priority than the current camera API client using this device. In general, if the top, foreground activity is running within your application process, your process will be given the highest priority when accessing the camera, and this method will succeed even if the camera device is in use by another camera API client. Any lower-priority application that loses control of the camera in this way will receive an StateCallback.onDisconnected callback.
Once the camera is successfully opened, StateCallback.onOpened will be invoked with the newly opened CameraDevice. The camera device can then be set up for operation by calling CameraDevice.createCaptureSession and CameraDevice.createCaptureRequest

If the camera becomes disconnected during initialization after this function call returns, StateCallback.onDisconnected with a CameraDevice in the disconnected state (and StateCallback.onOpened will be skipped).
If opening the camera device fails, then the device callback's onError method will be called, and subsequent calls on the camera device will throw a CameraAccessException.
Params: cameraId – 
            The unique identifier of the camera device to open
callback – 
            The callback which is invoked once the camera is opened
handler –  The handler on which the callback should be invoked, or null to use the current thread's looper.
Throws: CameraAccessException – if the camera is disabled by device policy,
has been disconnected, or is being used by a higher-priority camera API client.
IllegalArgumentException – if cameraId or the callback was null,
or the cameraId does not match any currently or previously available
camera device.
SecurityException – if the application does not have permission to
access the camera
See Also: getCameraIdList
DevicePolicyManager.setCameraDisabled/**
     * Open a connection to a camera with the given ID.
     *
     * <p>Use {@link #getCameraIdList} to get the list of available camera
     * devices. Note that even if an id is listed, open may fail if the device
     * is disconnected between the calls to {@link #getCameraIdList} and
     * {@link #openCamera}, or if a higher-priority camera API client begins using the
     * camera device.</p>
     *
     * <p>As of API level 23, devices for which the
     * {@link AvailabilityCallback#onCameraUnavailable(String)} callback has been called due to the
     * device being in use by a lower-priority, background camera API client can still potentially
     * be opened by calling this method when the calling camera API client has a higher priority
     * than the current camera API client using this device.  In general, if the top, foreground
     * activity is running within your application process, your process will be given the highest
     * priority when accessing the camera, and this method will succeed even if the camera device is
     * in use by another camera API client. Any lower-priority application that loses control of the
     * camera in this way will receive an
     * {@link android.hardware.camera2.CameraDevice.StateCallback#onDisconnected} callback.</p>
     *
     * <p>Once the camera is successfully opened, {@link CameraDevice.StateCallback#onOpened} will
     * be invoked with the newly opened {@link CameraDevice}. The camera device can then be set up
     * for operation by calling {@link CameraDevice#createCaptureSession} and
     * {@link CameraDevice#createCaptureRequest}</p>
     *
     * <!--
     * <p>Since the camera device will be opened asynchronously, any asynchronous operations done
     * on the returned CameraDevice instance will be queued up until the device startup has
     * completed and the callback's {@link CameraDevice.StateCallback#onOpened onOpened} method is
     * called. The pending operations are then processed in order.</p>
     * -->
     * <p>If the camera becomes disconnected during initialization
     * after this function call returns,
     * {@link CameraDevice.StateCallback#onDisconnected} with a
     * {@link CameraDevice} in the disconnected state (and
     * {@link CameraDevice.StateCallback#onOpened} will be skipped).</p>
     *
     * <p>If opening the camera device fails, then the device callback's
     * {@link CameraDevice.StateCallback#onError onError} method will be called, and subsequent
     * calls on the camera device will throw a {@link CameraAccessException}.</p>
     *
     * @param cameraId
     *             The unique identifier of the camera device to open
     * @param callback
     *             The callback which is invoked once the camera is opened
     * @param handler
     *             The handler on which the callback should be invoked, or
     *             {@code null} to use the current thread's {@link android.os.Looper looper}.
     *
     * @throws CameraAccessException if the camera is disabled by device policy,
     * has been disconnected, or is being used by a higher-priority camera API client.
     *
     * @throws IllegalArgumentException if cameraId or the callback was null,
     * or the cameraId does not match any currently or previously available
     * camera device.
     *
     * @throws SecurityException if the application does not have permission to
     * access the camera
     *
     * @see #getCameraIdList
     * @see android.app.admin.DevicePolicyManager#setCameraDisabled
     */
    @RequiresPermission(android.Manifest.permission.CAMERA)
    public void openCamera(@NonNull String cameraId,
            @NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler)
            throws CameraAccessException {

        openCameraForUid(cameraId, callback, CameraDeviceImpl.checkAndWrapHandler(handler),
                USE_CALLING_UID);
    }

    Open a connection to a camera with the given ID.
The behavior of this method matches that of openCamera(String, StateCallback, Handler), except that it uses Executor as an argument instead of Handler.
Params: cameraId – 
            The unique identifier of the camera device to open
executor – 
            The executor which will be used when invoking the callback.
callback – 
            The callback which is invoked once the camera is opened
Throws: CameraAccessException – if the camera is disabled by device policy,
has been disconnected, or is being used by a higher-priority camera API client.
IllegalArgumentException – if cameraId, the callback or the executor was null,
or the cameraId does not match any currently or previously available
camera device.
SecurityException – if the application does not have permission to
access the camera
See Also: getCameraIdList
DevicePolicyManager.setCameraDisabled/**
     * Open a connection to a camera with the given ID.
     *
     * <p>The behavior of this method matches that of
     * {@link #openCamera(String, StateCallback, Handler)}, except that it uses
     * {@link java.util.concurrent.Executor} as an argument instead of
     * {@link android.os.Handler}.</p>
     *
     * @param cameraId
     *             The unique identifier of the camera device to open
     * @param executor
     *             The executor which will be used when invoking the callback.
     * @param callback
     *             The callback which is invoked once the camera is opened
     *
     * @throws CameraAccessException if the camera is disabled by device policy,
     * has been disconnected, or is being used by a higher-priority camera API client.
     *
     * @throws IllegalArgumentException if cameraId, the callback or the executor was null,
     * or the cameraId does not match any currently or previously available
     * camera device.
     *
     * @throws SecurityException if the application does not have permission to
     * access the camera
     *
     * @see #getCameraIdList
     * @see android.app.admin.DevicePolicyManager#setCameraDisabled
     */
    @RequiresPermission(android.Manifest.permission.CAMERA)
    public void openCamera(@NonNull String cameraId,
            @NonNull @CallbackExecutor Executor executor,
            @NonNull final CameraDevice.StateCallback callback)
            throws CameraAccessException {
        if (executor == null) {
            throw new IllegalArgumentException("executor was null");
        }
        openCameraForUid(cameraId, callback, executor, USE_CALLING_UID);
    }

    Open a connection to a camera with the given ID, on behalf of another application
specified by clientUid.
The behavior of this method matches that of openCamera, except that it allows the caller to specify the UID to use for permission/etc verification. This can only be done by services trusted by the camera subsystem to act on behalf of applications and to forward the real UID.
Params: clientUid – 
            The UID of the application on whose behalf the camera is being opened.
            Must be USE_CALLING_UID unless the caller is a trusted service.
@hide /**
     * Open a connection to a camera with the given ID, on behalf of another application
     * specified by clientUid.
     *
     * <p>The behavior of this method matches that of {@link #openCamera}, except that it allows
     * the caller to specify the UID to use for permission/etc verification. This can only be
     * done by services trusted by the camera subsystem to act on behalf of applications and
     * to forward the real UID.</p>
     *
     * @param clientUid
     *             The UID of the application on whose behalf the camera is being opened.
     *             Must be USE_CALLING_UID unless the caller is a trusted service.
     *
     * @hide
     */
    public void openCameraForUid(@NonNull String cameraId,
            @NonNull final CameraDevice.StateCallback callback, @NonNull Executor executor,
            int clientUid)
            throws CameraAccessException {

        if (cameraId == null) {
            throw new IllegalArgumentException("cameraId was null");
        } else if (callback == null) {
            throw new IllegalArgumentException("callback was null");
        }
        if (CameraManagerGlobal.sCameraServiceDisabled) {
            throw new IllegalArgumentException("No cameras available on device");
        }

        openCameraDeviceUserAsync(cameraId, callback, executor, clientUid);
    }

    Set the flash unit's torch mode of the camera of the given ID without opening the camera
device.
Use getCameraIdList to get the list of available camera devices and use getCameraCharacteristics to check whether the camera device has a flash unit. Note that even if a camera device has a flash unit, turning on the torch mode may fail if the camera device or other camera resources needed to turn on the torch mode are in use. 
 If setTorchMode is called to turn on or off the torch mode successfully, TorchCallback.onTorchModeChanged will be invoked. However, even if turning on the torch mode is successful, the application does not have the exclusive ownership of the flash unit or the camera device. The torch mode will be turned off and becomes unavailable when the camera device that the flash unit belongs to becomes unavailable or when other camera resources to keep the torch on become unavailable ( TorchCallback.onTorchModeUnavailable will be invoked). Also, other applications are free to call setTorchMode to turn off the torch mode ( TorchCallback.onTorchModeChanged will be invoked). If the latest application that turned on the torch mode exits, the torch mode will be turned off. 
Params: cameraId – 
            The unique identifier of the camera device that the flash unit belongs to.
enabled –  The desired state of the torch mode for the target camera device. Set to true to turn on the torch mode. Set to false to turn off the torch mode.
Throws: CameraAccessException – if it failed to access the flash unit. CameraAccessException.CAMERA_IN_USE will be thrown if the camera device is in use. CameraAccessException.MAX_CAMERAS_IN_USE will be thrown if other camera resources needed to turn on the torch mode are in use. CameraAccessException.CAMERA_DISCONNECTED will be thrown if camera service is not available.
IllegalArgumentException – if cameraId was null, cameraId doesn't match any currently
            or previously available camera device, or the camera device doesn't have a
            flash unit./**
     * Set the flash unit's torch mode of the camera of the given ID without opening the camera
     * device.
     *
     * <p>Use {@link #getCameraIdList} to get the list of available camera devices and use
     * {@link #getCameraCharacteristics} to check whether the camera device has a flash unit.
     * Note that even if a camera device has a flash unit, turning on the torch mode may fail
     * if the camera device or other camera resources needed to turn on the torch mode are in use.
     * </p>
     *
     * <p> If {@link #setTorchMode} is called to turn on or off the torch mode successfully,
     * {@link CameraManager.TorchCallback#onTorchModeChanged} will be invoked.
     * However, even if turning on the torch mode is successful, the application does not have the
     * exclusive ownership of the flash unit or the camera device. The torch mode will be turned
     * off and becomes unavailable when the camera device that the flash unit belongs to becomes
     * unavailable or when other camera resources to keep the torch on become unavailable (
     * {@link CameraManager.TorchCallback#onTorchModeUnavailable} will be invoked). Also,
     * other applications are free to call {@link #setTorchMode} to turn off the torch mode (
     * {@link CameraManager.TorchCallback#onTorchModeChanged} will be invoked). If the latest
     * application that turned on the torch mode exits, the torch mode will be turned off.
     *
     * @param cameraId
     *             The unique identifier of the camera device that the flash unit belongs to.
     * @param enabled
     *             The desired state of the torch mode for the target camera device. Set to
     *             {@code true} to turn on the torch mode. Set to {@code false} to turn off the
     *             torch mode.
     *
     * @throws CameraAccessException if it failed to access the flash unit.
     *             {@link CameraAccessException#CAMERA_IN_USE} will be thrown if the camera device
     *             is in use. {@link CameraAccessException#MAX_CAMERAS_IN_USE} will be thrown if
     *             other camera resources needed to turn on the torch mode are in use.
     *             {@link CameraAccessException#CAMERA_DISCONNECTED} will be thrown if camera
     *             service is not available.
     *
     * @throws IllegalArgumentException if cameraId was null, cameraId doesn't match any currently
     *             or previously available camera device, or the camera device doesn't have a
     *             flash unit.
     */
    public void setTorchMode(@NonNull String cameraId, boolean enabled)
            throws CameraAccessException {
        if (CameraManagerGlobal.sCameraServiceDisabled) {
            throw new IllegalArgumentException("No cameras available on device");
        }
        CameraManagerGlobal.get().setTorchMode(cameraId, enabled);
    }

    A callback for camera devices becoming available or unavailable to open.
Cameras become available when they are no longer in use, or when a new
removable camera is connected. They become unavailable when some
application or service starts using a camera, or when a removable camera
is disconnected.
Extend this callback and pass an instance of the subclass to CameraManager.registerAvailabilityCallback to be notified of such availability changes.
See Also: registerAvailabilityCallback/**
     * A callback for camera devices becoming available or unavailable to open.
     *
     * <p>Cameras become available when they are no longer in use, or when a new
     * removable camera is connected. They become unavailable when some
     * application or service starts using a camera, or when a removable camera
     * is disconnected.</p>
     *
     * <p>Extend this callback and pass an instance of the subclass to
     * {@link CameraManager#registerAvailabilityCallback} to be notified of such availability
     * changes.</p>
     *
     * @see #registerAvailabilityCallback
     */
    public static abstract class AvailabilityCallback {

        A new camera has become available to use.
The default implementation of this method does nothing.
Params: cameraId – The unique identifier of the new camera./**
         * A new camera has become available to use.
         *
         * <p>The default implementation of this method does nothing.</p>
         *
         * @param cameraId The unique identifier of the new camera.
         */
        public void onCameraAvailable(@NonNull String cameraId) {
            // default empty implementation
        }

        A previously-available camera has become unavailable for use.
If an application had an active CameraDevice instance for the now-disconnected camera, that application will receive a disconnection error.
The default implementation of this method does nothing.
Params: cameraId – The unique identifier of the disconnected camera./**
         * A previously-available camera has become unavailable for use.
         *
         * <p>If an application had an active CameraDevice instance for the
         * now-disconnected camera, that application will receive a
         * {@link CameraDevice.StateCallback#onDisconnected disconnection error}.</p>
         *
         * <p>The default implementation of this method does nothing.</p>
         *
         * @param cameraId The unique identifier of the disconnected camera.
         */
        public void onCameraUnavailable(@NonNull String cameraId) {
            // default empty implementation
        }
    }

    A callback for camera flash torch modes becoming unavailable, disabled, or enabled.
The torch mode becomes unavailable when the camera device it belongs to becomes unavailable or other camera resources it needs become busy due to other higher priority camera activities. The torch mode becomes disabled when it was turned off or when the camera device it belongs to is no longer in use and other camera resources it needs are no longer busy. A camera's torch mode is turned off when an application calls setTorchMode to turn off the camera's torch mode, or when an application turns on another camera's torch mode if keeping multiple torch modes on simultaneously is not supported. The torch mode becomes enabled when it is turned on via setTorchMode.
The torch mode is available to set via setTorchMode only when it's in a disabled or enabled state.
Extend this callback and pass an instance of the subclass to CameraManager.registerTorchCallback to be notified of such status changes. 
See Also: registerTorchCallback/**
     * A callback for camera flash torch modes becoming unavailable, disabled, or enabled.
     *
     * <p>The torch mode becomes unavailable when the camera device it belongs to becomes
     * unavailable or other camera resources it needs become busy due to other higher priority
     * camera activities. The torch mode becomes disabled when it was turned off or when the camera
     * device it belongs to is no longer in use and other camera resources it needs are no longer
     * busy. A camera's torch mode is turned off when an application calls {@link #setTorchMode} to
     * turn off the camera's torch mode, or when an application turns on another camera's torch mode
     * if keeping multiple torch modes on simultaneously is not supported. The torch mode becomes
     * enabled when it is turned on via {@link #setTorchMode}.</p>
     *
     * <p>The torch mode is available to set via {@link #setTorchMode} only when it's in a disabled
     * or enabled state.</p>
     *
     * <p>Extend this callback and pass an instance of the subclass to
     * {@link CameraManager#registerTorchCallback} to be notified of such status changes.
     * </p>
     *
     * @see #registerTorchCallback
     */
    public static abstract class TorchCallback {
        A camera's torch mode has become unavailable to set via setTorchMode. If torch mode was previously turned on by calling setTorchMode, it will be turned off before onTorchModeUnavailable is invoked. setTorchMode will fail until the torch mode has entered a disabled or enabled state again.
The default implementation of this method does nothing.
Params: cameraId – The unique identifier of the camera whose torch mode has become
                unavailable./**
         * A camera's torch mode has become unavailable to set via {@link #setTorchMode}.
         *
         * <p>If torch mode was previously turned on by calling {@link #setTorchMode}, it will be
         * turned off before {@link CameraManager.TorchCallback#onTorchModeUnavailable} is
         * invoked. {@link #setTorchMode} will fail until the torch mode has entered a disabled or
         * enabled state again.</p>
         *
         * <p>The default implementation of this method does nothing.</p>
         *
         * @param cameraId The unique identifier of the camera whose torch mode has become
         *                 unavailable.
         */
        public void onTorchModeUnavailable(@NonNull String cameraId) {
            // default empty implementation
        }

        A camera's torch mode has become enabled or disabled and can be changed via setTorchMode. The default implementation of this method does nothing.
Params: cameraId – The unique identifier of the camera whose torch mode has been changed.
enabled – The state that the torch mode of the camera has been changed to. true when the torch mode has become on and available to be turned off. false when the torch mode has becomes off and available to be turned on./**
         * A camera's torch mode has become enabled or disabled and can be changed via
         * {@link #setTorchMode}.
         *
         * <p>The default implementation of this method does nothing.</p>
         *
         * @param cameraId The unique identifier of the camera whose torch mode has been changed.
         *
         * @param enabled The state that the torch mode of the camera has been changed to.
         *                {@code true} when the torch mode has become on and available to be turned
         *                off. {@code false} when the torch mode has becomes off and available to
         *                be turned on.
         */
        public void onTorchModeChanged(@NonNull String cameraId, boolean enabled) {
            // default empty implementation
        }
    }

    Convert ServiceSpecificExceptions and Binder RemoteExceptions from camera binder interfaces
into the correct public exceptions.
@hide /**
     * Convert ServiceSpecificExceptions and Binder RemoteExceptions from camera binder interfaces
     * into the correct public exceptions.
     *
     * @hide
     */
    public static void throwAsPublicException(Throwable t) throws CameraAccessException {
        if (t instanceof ServiceSpecificException) {
            ServiceSpecificException e = (ServiceSpecificException) t;
            int reason = CameraAccessException.CAMERA_ERROR;
            switch(e.errorCode) {
                case ICameraService.ERROR_DISCONNECTED:
                    reason = CameraAccessException.CAMERA_DISCONNECTED;
                    break;
                case ICameraService.ERROR_DISABLED:
                    reason = CameraAccessException.CAMERA_DISABLED;
                    break;
                case ICameraService.ERROR_CAMERA_IN_USE:
                    reason = CameraAccessException.CAMERA_IN_USE;
                    break;
                case ICameraService.ERROR_MAX_CAMERAS_IN_USE:
                    reason = CameraAccessException.MAX_CAMERAS_IN_USE;
                    break;
                case ICameraService.ERROR_DEPRECATED_HAL:
                    reason = CameraAccessException.CAMERA_DEPRECATED_HAL;
                    break;
                case ICameraService.ERROR_ILLEGAL_ARGUMENT:
                case ICameraService.ERROR_ALREADY_EXISTS:
                    throw new IllegalArgumentException(e.getMessage(), e);
                case ICameraService.ERROR_PERMISSION_DENIED:
                    throw new SecurityException(e.getMessage(), e);
                case ICameraService.ERROR_TIMED_OUT:
                case ICameraService.ERROR_INVALID_OPERATION:
                default:
                    reason = CameraAccessException.CAMERA_ERROR;
            }
            throw new CameraAccessException(reason, e.getMessage(), e);
        } else if (t instanceof DeadObjectException) {
            throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
                    "Camera service has died unexpectedly",
                    t);
        } else if (t instanceof RemoteException) {
            throw new UnsupportedOperationException("An unknown RemoteException was thrown" +
                    " which should never happen.", t);
        } else if (t instanceof RuntimeException) {
            RuntimeException e = (RuntimeException) t;
            throw e;
        }
    }

    Queries the camera service if it supports the camera2 api directly, or needs a shim.
Params: cameraId – a non-null camera identifier
Returns: false if the legacy shim needs to be used, true otherwise./**
     * Queries the camera service if it supports the camera2 api directly, or needs a shim.
     *
     * @param cameraId a non-{@code null} camera identifier
     * @return {@code false} if the legacy shim needs to be used, {@code true} otherwise.
     */
    private boolean supportsCamera2ApiLocked(String cameraId) {
        return supportsCameraApiLocked(cameraId, API_VERSION_2);
    }

    Queries the camera service if it supports a camera api directly, or needs a shim.
Params: cameraId – a non-null camera identifier
apiVersion – the version, i.e. API_VERSION_1 or API_VERSION_2
Returns: true if connecting will work for that device version./**
     * Queries the camera service if it supports a camera api directly, or needs a shim.
     *
     * @param cameraId a non-{@code null} camera identifier
     * @param apiVersion the version, i.e. {@code API_VERSION_1} or {@code API_VERSION_2}
     * @return {@code true} if connecting will work for that device version.
     */
    private boolean supportsCameraApiLocked(String cameraId, int apiVersion) {
        /*
         * Possible return values:
         * - NO_ERROR => CameraX API is supported
         * - CAMERA_DEPRECATED_HAL => CameraX API is *not* supported (thrown as an exception)
         * - Remote exception => If the camera service died
         *
         * Anything else is an unexpected error we don't want to recover from.
         */
        try {
            ICameraService cameraService = CameraManagerGlobal.get().getCameraService();
            // If no camera service, no support
            if (cameraService == null) return false;

            return cameraService.supportsCameraApi(cameraId, apiVersion);
        } catch (RemoteException e) {
            // Camera service is now down, no support for any API level
        }
        return false;
    }

    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
/**
     * 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
            implements IBinder.DeathRecipient {

        private static final String TAG = "CameraManagerGlobal";
        private final boolean DEBUG = false;

        private final int CAMERA_SERVICE_RECONNECT_DELAY_MS = 1000;

        // Singleton instance
        private static final CameraManagerGlobal gCameraManager =
            new CameraManagerGlobal();

        This must match the ICameraService definition
/**
         * This must match the ICameraService definition
         */
        private static final String CAMERA_SERVICE_BINDER_NAME = "media.camera";

        private final ScheduledExecutorService mScheduler = Executors.newScheduledThreadPool(1);
        // Camera ID -> Status map
        private final ArrayMap<String, Integer> mDeviceStatus = new ArrayMap<String, Integer>();

        // Registered availablility callbacks and their executors
        private final ArrayMap<AvailabilityCallback, Executor> mCallbackMap =
            new ArrayMap<AvailabilityCallback, Executor>();

        // torch client binder to set the torch mode with.
        private Binder mTorchClientBinder = new Binder();

        // Camera ID -> Torch status map
        private final ArrayMap<String, Integer> mTorchStatus = new ArrayMap<String, Integer>();

        // Registered torch callbacks and their executors
        private final ArrayMap<TorchCallback, Executor> mTorchCallbackMap =
                new ArrayMap<TorchCallback, Executor>();

        private final Object mLock = new Object();

        // Access only through getCameraService to deal with binder death
        private ICameraService mCameraService;

        // Singleton, don't allow construction
        private CameraManagerGlobal() {
        }

        public static final boolean sCameraServiceDisabled =
                SystemProperties.getBoolean("config.disable_cameraservice", false);

        public static CameraManagerGlobal get() {
            return gCameraManager;
        }

        @Override
        public IBinder asBinder() {
            return this;
        }

        Return a best-effort ICameraService.
This will be null if the camera service is not currently available. If the camera
service has died since the last use of the camera service, will try to reconnect to the
service.
/**
         * Return a best-effort ICameraService.
         *
         * <p>This will be null if the camera service is not currently available. If the camera
         * service has died since the last use of the camera service, will try to reconnect to the
         * service.</p>
         */
        public ICameraService getCameraService() {
            synchronized(mLock) {
                connectCameraServiceLocked();
                if (mCameraService == null && !sCameraServiceDisabled) {
                    Log.e(TAG, "Camera service is unavailable");
                }
                return mCameraService;
            }
        }

        Connect to the camera service if it's available, and set up listeners.
If the service is already connected, do nothing.
Sets mCameraService to a valid pointer or null if the connection does not succeed.
/**
         * Connect to the camera service if it's available, and set up listeners.
         * If the service is already connected, do nothing.
         *
         * <p>Sets mCameraService to a valid pointer or null if the connection does not succeed.</p>
         */
        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);
                }
                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
            }
        }

        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.
/**
         * 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();

                int idCount = 0;
                for (int i = 0; i < mDeviceStatus.size(); i++) {
                    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++) {
                    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::getAPI1CompatibleCameraDeviceIds
            Arrays.sort(cameraIds, new Comparator<String>() {
                    @Override
                    public 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 first
                        if (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 uint
                            return s1.compareTo(s2);
                        }
                    }});
            return cameraIds;
        }

        public void setTorchMode(String cameraId, boolean enabled) throws CameraAccessException {
            synchronized(mLock) {

                if (cameraId == null) {
                    throw new IllegalArgumentException("cameraId was null");
                }

                ICameraService cameraService = getCameraService();
                if (cameraService == null) {
                    throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
                        "Camera service is currently unavailable");
                }

                try {
                    cameraService.setTorchMode(cameraId, enabled, mTorchClientBinder);
                } catch(ServiceSpecificException e) {
                    throwAsPublicException(e);
                } catch (RemoteException e) {
                    throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
                            "Camera service is currently unavailable");
                }
            }
        }

        private void handleRecoverableSetupErrors(ServiceSpecificException e) {
            switch (e.errorCode) {
                case ICameraService.ERROR_DISCONNECTED:
                    Log.w(TAG, e.getMessage());
                    break;
                default:
                    throw new IllegalStateException(e);
            }
        }

        private boolean isAvailable(int status) {
            switch (status) {
                case ICameraServiceListener.STATUS_PRESENT:
                    return true;
                default:
                    return false;
            }
        }

        private boolean validStatus(int status) {
            switch (status) {
                case ICameraServiceListener.STATUS_NOT_PRESENT:
                case ICameraServiceListener.STATUS_PRESENT:
                case ICameraServiceListener.STATUS_ENUMERATING:
                case ICameraServiceListener.STATUS_NOT_AVAILABLE:
                    return true;
                default:
                    return false;
            }
        }

        private boolean validTorchStatus(int status) {
            switch (status) {
                case ICameraServiceListener.TORCH_STATUS_NOT_AVAILABLE:
                case ICameraServiceListener.TORCH_STATUS_AVAILABLE_ON:
                case ICameraServiceListener.TORCH_STATUS_AVAILABLE_OFF:
                    return true;
                default:
                    return false;
            }
        }

        private void postSingleUpdate(final AvailabilityCallback callback, final Executor executor,
                final String id, final int status) {
            if (isAvailable(status)) {
                final long ident = Binder.clearCallingIdentity();
                try {
                    executor.execute(
                        new Runnable() {
                            @Override
                            public void run() {
                                callback.onCameraAvailable(id);
                            }
                        });
                } finally {
                    Binder.restoreCallingIdentity(ident);
                }
            } else {
                final long ident = Binder.clearCallingIdentity();
                try {
                    executor.execute(
                        new Runnable() {
                            @Override
                            public void run() {
                                callback.onCameraUnavailable(id);
                            }
                        });
                } finally {
                    Binder.restoreCallingIdentity(ident);
                }
            }
        }

        private void postSingleTorchUpdate(final TorchCallback callback, final Executor executor,
                final String id, final int status) {
            switch(status) {
                case ICameraServiceListener.TORCH_STATUS_AVAILABLE_ON:
                case ICameraServiceListener.TORCH_STATUS_AVAILABLE_OFF: {
                        final long ident = Binder.clearCallingIdentity();
                        try {
                            executor.execute(() -> {
                                callback.onTorchModeChanged(id, status ==
                                        ICameraServiceListener.TORCH_STATUS_AVAILABLE_ON);
                            });
                        } finally {
                            Binder.restoreCallingIdentity(ident);
                        }
                    }
                    break;
                default: {
                        final long ident = Binder.clearCallingIdentity();
                        try {
                            executor.execute(() -> {
                                callback.onTorchModeUnavailable(id);
                            });
                        } finally {
                            Binder.restoreCallingIdentity(ident);
                        }
                    }
                    break;
            }
        }

        Send the state of all known cameras to the provided listener, to initialize
the listener's knowledge of camera state.
/**
         * Send the state of all known cameras to the provided listener, to initialize
         * the listener's knowledge of camera state.
         */
        private void updateCallbackLocked(AvailabilityCallback callback, Executor executor) {
            for (int i = 0; i < mDeviceStatus.size(); i++) {
                String id = mDeviceStatus.keyAt(i);
                Integer status = mDeviceStatus.valueAt(i);
                postSingleUpdate(callback, executor, id, status);
            }
        }

        private void onStatusChangedLocked(int status, String id) {
            if (DEBUG) {
                Log.v(TAG,
                        String.format("Camera id %s has status changed to 0x%x", id, status));
            }

            if (!validStatus(status)) {
                Log.e(TAG, String.format("Ignoring invalid device %s status 0x%x", id,
                                status));
                return;
            }

            Integer oldStatus;
            if (status == ICameraServiceListener.STATUS_NOT_PRESENT) {
                oldStatus = mDeviceStatus.remove(id);
            } else {
                oldStatus = mDeviceStatus.put(id, status);
            }

            if (oldStatus != null && oldStatus == status) {
                if (DEBUG) {
                    Log.v(TAG, String.format(
                        "Device status changed to 0x%x, which is what it already was",
                        status));
                }
                return;
            }

            // TODO: consider abstracting out this state minimization + transition
            // into a separate
            // more easily testable class
            // i.e. (new State()).addState(STATE_AVAILABLE)
            //                   .addState(STATE_NOT_AVAILABLE)
            //                   .addTransition(STATUS_PRESENT, STATE_AVAILABLE),
            //                   .addTransition(STATUS_NOT_PRESENT, STATE_NOT_AVAILABLE)
            //                   .addTransition(STATUS_ENUMERATING, STATE_NOT_AVAILABLE);
            //                   .addTransition(STATUS_NOT_AVAILABLE, STATE_NOT_AVAILABLE);

            // Translate all the statuses to either 'available' or 'not available'
            //  available -> available         => no new update
            //  not available -> not available => no new update
            if (oldStatus != null && isAvailable(status) == isAvailable(oldStatus)) {
                if (DEBUG) {
                    Log.v(TAG,
                            String.format(
                                "Device status was previously available (%b), " +
                                " and is now again available (%b)" +
                                "so no new client visible update will be sent",
                                isAvailable(oldStatus), isAvailable(status)));
                }
                return;
            }

            final int callbackCount = mCallbackMap.size();
            for (int i = 0; i < callbackCount; i++) {
                Executor executor = mCallbackMap.valueAt(i);
                final AvailabilityCallback callback = mCallbackMap.keyAt(i);

                postSingleUpdate(callback, executor, id, status);
            }
        } // onStatusChangedLocked

        private void updateTorchCallbackLocked(TorchCallback callback, Executor executor) {
            for (int i = 0; i < mTorchStatus.size(); i++) {
                String id = mTorchStatus.keyAt(i);
                Integer status = mTorchStatus.valueAt(i);
                postSingleTorchUpdate(callback, executor, id, status);
            }
        }

        private void onTorchStatusChangedLocked(int status, String id) {
            if (DEBUG) {
                Log.v(TAG,
                        String.format("Camera id %s has torch status changed to 0x%x", id, status));
            }

            if (!validTorchStatus(status)) {
                Log.e(TAG, String.format("Ignoring invalid device %s torch status 0x%x", id,
                                status));
                return;
            }

            Integer oldStatus = mTorchStatus.put(id, status);
            if (oldStatus != null && oldStatus == status) {
                if (DEBUG) {
                    Log.v(TAG, String.format(
                        "Torch status changed to 0x%x, which is what it already was",
                        status));
                }
                return;
            }

            final int callbackCount = mTorchCallbackMap.size();
            for (int i = 0; i < callbackCount; i++) {
                final Executor executor = mTorchCallbackMap.valueAt(i);
                final TorchCallback callback = mTorchCallbackMap.keyAt(i);
                postSingleTorchUpdate(callback, executor, id, status);
            }
        } // onTorchStatusChangedLocked

        Register a callback to be notified about camera device availability with the
global listener singleton.
Params: callback – the new callback to send camera availability notices to
executor – The executor which should invoke the callback. May not be null./**
         * Register a callback to be notified about camera device availability with the
         * global listener singleton.
         *
         * @param callback the new callback to send camera availability notices to
         * @param executor The executor which should invoke the callback. May not be null.
         */
        public void registerAvailabilityCallback(AvailabilityCallback callback, Executor executor) {
            synchronized (mLock) {
                connectCameraServiceLocked();

                Executor oldExecutor = mCallbackMap.put(callback, executor);
                // For new callbacks, provide initial availability information
                if (oldExecutor == null) {
                    updateCallbackLocked(callback, executor);
                }

                // If not connected to camera service, schedule a reconnect to camera service.
                if (mCameraService == null) {
                    scheduleCameraServiceReconnectionLocked();
                }
            }
        }

        Remove a previously-added callback; the callback will no longer receive connection and
disconnection callbacks, and is no longer referenced by the global listener singleton.
Params: callback – The callback to remove from the notification list/**
         * Remove a previously-added callback; the callback will no longer receive connection and
         * disconnection callbacks, and is no longer referenced by the global listener singleton.
         *
         * @param callback The callback to remove from the notification list
         */
        public void unregisterAvailabilityCallback(AvailabilityCallback callback) {
            synchronized (mLock) {
                mCallbackMap.remove(callback);
            }
        }

        public void registerTorchCallback(TorchCallback callback, Executor executor) {
            synchronized(mLock) {
                connectCameraServiceLocked();

                Executor oldExecutor = mTorchCallbackMap.put(callback, executor);
                // For new callbacks, provide initial torch information
                if (oldExecutor == null) {
                    updateTorchCallbackLocked(callback, executor);
                }

                // If not connected to camera service, schedule a reconnect to camera service.
                if (mCameraService == null) {
                    scheduleCameraServiceReconnectionLocked();
                }
            }
        }

        public void unregisterTorchCallback(TorchCallback callback) {
            synchronized(mLock) {
                mTorchCallbackMap.remove(callback);
            }
        }

        Callback from camera service notifying the process about camera availability changes
/**
         * Callback from camera service notifying the process about camera availability changes
         */
        @Override
        public void onStatusChanged(int status, String cameraId) throws RemoteException {
            synchronized(mLock) {
                onStatusChangedLocked(status, cameraId);
            }
        }

        @Override
        public void onTorchStatusChanged(int status, String cameraId) throws RemoteException {
            synchronized (mLock) {
                onTorchStatusChangedLocked(status, cameraId);
            }
        }

        Try to connect to camera service after some delay if any client registered camera
availability callback or torch status callback.
/**
         * Try to connect to camera service after some delay if any client registered camera
         * availability callback or torch status callback.
         */
        private void scheduleCameraServiceReconnectionLocked() {
            if (mCallbackMap.isEmpty() && mTorchCallbackMap.isEmpty()) {
                // Not necessary to reconnect camera service if no client registers a callback.
                return;
            }

            if (DEBUG) {
                Log.v(TAG, "Reconnecting Camera Service in " + CAMERA_SERVICE_RECONNECT_DELAY_MS +
                        " ms");
            }

            try {
                mScheduler.schedule(() -> {
                    ICameraService cameraService = getCameraService();
                    if (cameraService == null) {
                        synchronized(mLock) {
                            if (DEBUG) {
                                Log.v(TAG, "Reconnecting Camera Service failed.");
                            }
                            scheduleCameraServiceReconnectionLocked();
                        }
                    }
                }, CAMERA_SERVICE_RECONNECT_DELAY_MS, TimeUnit.MILLISECONDS);
            } catch (RejectedExecutionException e) {
                Log.e(TAG, "Failed to schedule camera service re-connect: " + e);
            }
        }

        Listener for camera service death.
The camera service isn't supposed to die under any normal circumstances, but can be
turned off during debug, or crash due to bugs.  So detect that and null out the interface
object, so that the next calls to the manager can try to reconnect.
/**
         * Listener for camera service death.
         *
         * <p>The camera service isn't supposed to die under any normal circumstances, but can be
         * turned off during debug, or crash due to bugs.  So detect that and null out the interface
         * object, so that the next calls to the manager can try to reconnect.</p>
         */
        public void binderDied() {
            synchronized(mLock) {
                // Only do this once per service death
                if (mCameraService == null) return;

                mCameraService = null;

                // Tell listeners that the cameras and torch modes are unavailable and schedule a
                // reconnection to camera service. When camera service is reconnected, the camera
                // and torch statuses will be updated.
                for (int i = 0; i < mDeviceStatus.size(); i++) {
                    String cameraId = mDeviceStatus.keyAt(i);
                    onStatusChangedLocked(ICameraServiceListener.STATUS_NOT_PRESENT, cameraId);
                }
                for (int i = 0; i < mTorchStatus.size(); i++) {
                    String cameraId = mTorchStatus.keyAt(i);
                    onTorchStatusChangedLocked(ICameraServiceListener.TORCH_STATUS_NOT_AVAILABLE,
                            cameraId);
                }

                scheduleCameraServiceReconnectionLocked();
            }
        }

    } // CameraManagerGlobal

} // CameraManager
Params:	callback – the new callback to send camera availability notices to handler – The handler on which the callback should be invoked, or `null` to use the current thread's `looper`.
Throws:	IllegalArgumentException – if the handler is `null` but the current thread has no looper.
Params:	executor – The executor which will be used to invoke the callback. callback – the new callback to send camera availability notices to
Throws:	IllegalArgumentException – if the executor is `null`.
Params:	callback – The new callback to send torch mode status to handler – The handler on which the callback should be invoked, or `null` to use the current thread's `looper`.
Throws:	IllegalArgumentException – if the handler is `null` but the current thread has no looper.
Params:	cameraId – The id of the camera device to query
Throws:	IllegalArgumentException – if the cameraId does not match any known camera device. CameraAccessException – if the camera device has been disconnected.
See Also:	getCameraIdList DevicePolicyManager.setCameraDisabled
Returns:	The properties of the given camera
Params:	cameraId – The unique identifier of the camera device to open callback – The callback for the camera. Must not be null. executor – The executor to invoke the callback with. Must not be null. uid – The UID of the application actually opening the camera. Must be USE_CALLING_UID unless the caller is a service that is trusted to open the device on behalf of an application and to forward the real UID.
Throws:	CameraAccessException – if the camera is disabled by device policy, too many camera devices are already open, or the cameraId does not match any currently available camera device. SecurityException – if the application does not have permission to access the camera IllegalArgumentException – if callback or handler is null.
See Also:	getCameraIdList DevicePolicyManager.setCameraDisabled
Returns:	A handle to the newly-created camera device.
Params:	clientUid – The UID of the application on whose behalf the camera is being opened. Must be USE_CALLING_UID unless the caller is a trusted service.
@hide
Params:	cameraId – a non-`null` camera identifier
Returns:	`false` if the legacy shim needs to be used, `true` otherwise.
/

android/ android-9.0.0_r35/ android/hardware/camera2/CameraManager.java
