Undefined variable "internal" or class "internal.​findSubCla​sses" when USB storage plugged in / pulled out

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MOC
MOC 2019-5-7
回答： Pruthvi Muppavarapu 2019-5-14
I have a new installation of Matlab R2016b on a Win10 machine.
Following error occurs when I plug in different usb storages:
Warning: Error occurred while executing the listener callback for event DeviceAdded defined for class internal.hotplug.EventSource:
Undefined variable "internal" or class "internal.findSubClasses".
Error in internal.deviceplugindetection.Manager/updateSubClasses (line 212)
subClasses = internal.findSubClasses( ...
Error in internal.deviceplugindetection.Manager/usbDeviceInsertedCallback (line 87)
obj.updateSubClasses();
Error in internal.deviceplugindetection.Manager>@(source,info)obj.usbDeviceInsertedCallback(info) (line 179)
@(source, info) obj.usbDeviceInsertedCallback(info));
Error in internal.hotplug.EventSource/onCustomEvent (line 77)
notify(obj, type, internal.hotplug.EventData(...
Error in internal.hotplug.EventSource>@(varargin)obj.onCustomEvent(varargin{:}) (line 62)
'Custom', @obj.onCustomEvent );
Error in asyncio.Channel/onCustomEvent (line 451)
notify(obj, 'Custom', asyncio.CustomEventInfo(type,data));
Error in asyncio.Channel>@(source,data)obj.onCustomEvent(data.Type,data.Data) (line 362)
@(source, data) obj.onCustomEvent(data.Type, data.Data));
> In internal.hotplug.EventSource/onCustomEvent (line 77)
In internal.hotplug.EventSource>@(varargin)obj.onCustomEvent(varargin{:}) (line 62)
In asyncio.Channel/onCustomEvent (line 451)
In asyncio.Channel>@(source,data)obj.onCustomEvent(data.Type,data.Data) (line 362)
If I pull out a USB storage, following error occurs:
Warning: Error occurred while executing the listener callback for event DeviceRemoved defined for class internal.hotplug.EventSource:
Undefined variable "internal" or class "internal.findSubClasses".
Error in internal.deviceplugindetection.Manager/updateSubClasses (line 212)
subClasses = internal.findSubClasses( ...
Error in internal.deviceplugindetection.Manager/usbDeviceRemovedCallback (line 131)
obj.updateSubClasses();
Error in internal.deviceplugindetection.Manager>@(source,info)obj.usbDeviceRemovedCallback(info) (line 185)
@(source, info) obj.usbDeviceRemovedCallback(info));
Error in internal.hotplug.EventSource/onCustomEvent (line 77)
notify(obj, type, internal.hotplug.EventData(...
Error in internal.hotplug.EventSource>@(varargin)obj.onCustomEvent(varargin{:}) (line 62)
'Custom', @obj.onCustomEvent );
Error in asyncio.Channel/onCustomEvent (line 451)
notify(obj, 'Custom', asyncio.CustomEventInfo(type,data));
Error in asyncio.Channel>@(source,data)obj.onCustomEvent(data.Type,data.Data) (line 362)
@(source, data) obj.onCustomEvent(data.Type, data.Data));
> In internal.hotplug.EventSource/onCustomEvent (line 77)
In internal.hotplug.EventSource>@(varargin)obj.onCustomEvent(varargin{:}) (line 62)
In asyncio.Channel/onCustomEvent (line 451)
In asyncio.Channel>@(source,data)obj.onCustomEvent(data.Type,data.Data) (line 362)
Unforntunately,
restoredefaultpath
rehash toolboxcache
savepath
did not help.
Any suggestions?
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Guillaume
Guillaume 2019-5-9
Well, it does look that there is something wrong with the instrument control toolbox if you could see the app icon but tmtool wasn't found.It's probably related to the error you see.
Unfortunately, only Mathworks may be able to help you here. If you have support, I would recommend to contact them. Otherwise, a complete uninstall (including user prefs) and reinstall (possibly without the ICT) may cure the problem.

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回答（1 个）

Pruthvi Muppavarapu
Hi Oliver,
A probable cause of your error might be related to the Instrument Control Toolbox. Please try executing the following command in the command window to verify the version of the toolbox installed and its compatibility with MATLAB release.
>>ver
If you do not see the toolbox and you believe that it is installed, try resetting the MATLAB path to the default. MATLAB stores the toolbox information in a cache file. You will need to first update this cache and then reset the path. To do this:
1. Go to the "File" menu to "Preferences"
2. Go to the "General" heading. Click the button "Update Toolbox Path Cache" and press "OK".
3. Go to the "File" menu to "Set Path"
4. Click on "Default", press "OK" to change, then click "Save" and finally "Close".
(If you have added any custom paths to MATLAB, you will need to restore those later)
Run "ver" again to see if the toolbox is installed. If not, you may need to reinstall this toolbox in order to use this function.
Once "ver" shows your toolbox, run the following command to see if you can find that function:
>>which -all <function_name>
Replacing "tmtool" with the name of the function. You should be presented with the path(s) of the function file. If you get "TMTOOL not found", you may need to reinstall that toolbox for the function to be active.
If you receive the error message "Has no license available" there is a licensing related issue preventing you from using that function. You may have to install a licensed version of the toolbox to resolve the issue.
After resolving the IC Toolbox issue, you may use it without the USB error as well. Hope this answer helps.
Regards,
Pruthvi

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