You should implemente a similar method as the ON/OFF buttons. Basically, when you move the slider you need to send those PWM/slider values to the ESP32 (like you would do with the buttons):

but how can i get the value from the slider in my code?, the problem is that the value is integer

// Setup callback when new value is received (from the Android application)
class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string rxValue = pCharacteristic->getValue();

if(rxValue.length() > 0) {
Serial.print(“Received value: “);
for(int i = 0; i < rxValue.length(); i++) {
Serial.print(rxValue[i]);
}

ledcWrite(ledChannel,atoi(rxValue) );

}
}
};

do not kwon what to do

What does it print in your serial monitor?

Error rxValue must be unit_32, so i have the problem in the mit app i can’t save the slider value as string or i do not kwon how do that, (that will solve my porblem) or how can i get in my arduino’s code a function that recives integer number o unit_32

But which code line is giving you that error? Unfortunately I’m not understanding your exact problem. This is a variable conversion error. What’s the rxValue variable type and which type do you need?

class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string rxValue = pCharacteristic->getValue();
if(rxValue.length() > 0) {
Serial.print(“Received value: “);
for(int i = 0; i < rxValue.length(); i++) {
Serial.print(rxValue[i]);
}
here is the problem pwm use led channel and an integer for duty cycle but rxvalue is a String and MIT APP inventor doesn't send the slider value as a string so i must send it as a byte or as integer and that is the problem i'll never will eable to get that value because rxvalue just receives Strings

You can convert a String to an integer using the .toInt() method. You can find more information about that function here: https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/toint/