there is no vlaue alarm general after decode

there is no value in position object for general alarm. how to ger general alarm value?

What do you mean by value? It's either present or not.

please attention to io252 and alarm-> general in this photo, why there is different beetween io252 and alarm in this picture? io252 must be powercut when we decode data

Because those are completely different types of attributes.

decoder dose not convert 252 id to powercut string in this method:

    register(252, fmbxxx, (p, b) -> {
        p.addAlarm(b.readUnsignedByte() > 0 ? Position.ALARM_POWER_CUT : null);
    });

i edited above code to traacar refrence.