ESP32 send the DHT11's data to android

I am writing the program on ESP32. I want the DHT11’s data that sent to Android via Bluetooth. However, I have a error about the invalid conversion.

#include <SimpleDHT.h>
#include <BluetoothSerial.h>

#define DHT11_PIN 7
SimpleDHT11 chk(DHT11_PIN);
BluetoothSerial SerialBT; 
void setup() 
{
    Serial.begin(9600);
    Serial.println("Enter AT commands:");
 
    // HC-06 default serial speed is 9600
    BTserial.begin("BLETEST");
}
 
void loop()
{
    String output = "";
    String tokenizer = "@";

    byte temperature = 0;
    byte humidity = 0;
    int err = SimpleDHTErrSuccess;
    if ((err = chk.read(&temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
    Serial.print("Read DHT11 failed, err="); 
    Serial.println(err);
    delay(1000);
    return;
  }
   
  
    // Keep reading from HC-06 and send to Arduino Serial Monitor
        if (SerialBT.available())
        {  
          
          Serial.write(SerialBT.read());
        }
   Serial.print((int)temperature); Serial.print(" *C, "); 
   Serial.print((int)humidity); Serial.println(" H");
 
    // Keep reading from Arduino Serial Monitor and send to HC-06
         //dummy data
       SerialBT.write("@");
          output.concat(tokenizer);
          
          if ((int)temperature != -999.00 || (int)humidity != -999.00){
                
              if((int)temperature != -999.00){
                  output.concat((int)temperature);         
                  output.concat(";");  
              }
              if((int)humidity != -999.00){            
                output.concat((int)humidity);        
                output.concat(";");
              }
              output.concat("0.00@");
          
              Serial.println(output);
              SerialBT.write(output.c_str());
              SerialBT.write("@100.25;100.00;100.00@");
          }
          delay(10);
     delay(500);
}

The error message:

C:\Users\yiu_c\OneDrive\桌面\arduino\bt-weather-arduino\bt-weather-arduino.ino: In function ‘void loop()’:

bt-weather-arduino:57:26: error: invalid conversion from ‘const char*’ to ‘uint8_t {aka unsigned char}’ [-fpermissive]

In file included from C:\Users\yiu_c\OneDrive\桌面\arduino\bt-weather-arduino\bt-weather-arduino.ino:5:0:

C:\Users\yiu_c\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.2\libraries\BluetoothSerial\src/BluetoothSerial.h:38:16: note: initializing argument 1 of ‘virtual size_t BluetoothSerial::write(uint8_t)’

size_t write(uint8_t c);

How can put the variable of string in SerialBT.write? In this situation, the variable of string cannot put in function of SerialBT.write.
Have anyone can solve this problem?

SerialBT.write("@");

If you use double quotes the compiler sees a string (char array). The write method needs a characters and not an array of characters. So use single quotes:

SerialBT.write('@');

and it probably is happy.