RFID-RC522 changing values in variable dataBlock[]

Hello everyone.

Few days I have studying a examples from library for RFID-RC522, but I have one issue.

In a library example ReadandWrite I am labouring with function Serial.read().

Goal is a saving a values into variables dataBlock[0], dataBlock[1]...

I have changed a for cycles and buffer. But still I cannot save a vules into variable dataBlock[].

Thanks for your help.

    byte sector         = 1;    //budeme zapisovat do sektoru 1

    
    byte blockAddr      = 4;    //od adresy bloku 4


    byte dataBlock[] = {};


    Serial.println("Prvni");


    dataBlock[0, HEX] = Serial.read();


    Serial.println(dataBlock[0]);


    delay(5000);


    Serial.println("Druha");


    dataBlock[1, HEX] = Serial.read();


    Serial.println(dataBlock[1]);


    delay(5000);


    Serial.println("Treti");


    dataBlock[2, HEX] = Serial.read();


    Serial.println(dataBlock[2]);


    delay(5000);


   Serial.println("Ctvrta");

   
    dataBlock[3, HEX] = Serial.read();


    Serial.println(dataBlock[3]);


    delay(5000);

    
    byte trailerBlock   = 7;    // do adresy bloku 

    
    MFRC522::StatusCode status;

    
    byte buffer[6];    // 6, protoze dva bity jsou kontrolni

    
    byte size = sizeof(buffer);   // dojde k ukonceni, pokud je hodnota stejna jako buffer