Computed Attributes - Help with testing the ignition status of Meiligao devices

Hello all,

From what I understand from the examples in the Traccar documentation pages regarding Computed Attributes this should work, it does not, at least not with the Meiligao device I'm working with...

Ignition
status ? (status & 0x0800) : false
boolean

I have also tried....

Ignition
status ? (status & 2048) : false
boolean

Which does not work either. What am I doing wrong?

Your expression returns int value. You should return boolean with something like this:

status ? (status & 0x0800 > 0) : false

The expression...

status ? (status & 0x0800 > 0) : false

errors and returns this....

"Error
Invalid parameter or constraints violation

java.lang.Long cannot be cast to java.lang.Boolean - ClassCastException (AttributeResource:57 < ...)"

I think "status" is a string, no?

Brackets missing:

status ? ((status & 0x0800) > 0) : false

status ? ((status & 0x0800) > 0) : false

The above expression always returns false.

It means that status doesn't have bit that you are expecting.

It is set, I'm sure of it

It looks like status is stored as a string in MeiligaoProtocolDecoder.java

Changing the code at around line 256 to store it in flags as an integer seems to have fixed it.

is this change to store status in flags as integer already done in the code?

I am trying get Ignition status from 'status' using computed attribute however it returns the following error.

'For input string: "0A00" - NumberFormatException (... < ComputedAttributesHandler:86 < AttributeResource:51 < ...)'

Any help would be highly appreciated.

It means that value is a string, so you need to convert it to integer first.

Hello Anton,

I tried taking hints from this post https://www.traccar.org/forums/topic/doubt-with-computed-attributes-protocol-suntech/ on converting strings to integer, however i kept getting errors for jexel.

the status value is as following

ign of status value 0201 = 0000 0010 0000 0001
and
ign on status value OA01 = 0000 1010 0000 0001

and from this post i took the computted attribute example status ? ((status & 0x0800) > 0) : false

and tried this status ? (((new ("java.lang.Integer", status)) & 0x0800) > 0) : false also tried few other approach, but i am surely making some mistake,

could you please help me on this again.

You can try something like this to convert string to int:

new("java.lang.Integer", 0).parseInt(status, 16)

Thanks Anton,

Sharing in-case it comes of use to any other user in the future. the computed attribute that worked for me for Meiligao Protocol device to detect ignition status.

status ? ((new("java.lang.Integer", 0).parseInt(status, 16) & 0x0800) > 0) : false

hi
I am also trying to get ignition status working with meitrack T366 as it doesnt appear automatically
when i try add computed attribute as above, i can click test without saving it and it returns 'false' as id expect but as soon as i save it and then go back and view it, it shows and error and the string is changed to status ? ((new(";java.lang.Integer";, 0).parseInt(status, 16) & 0x0400) > 0) : false

traccar seems to be substituting the " for &#34 and this throws an error when testing

Don't modify it once you created computed attribute.