Can’t split String when using BlutoothSerial

  android, arduino, c++, esp32, split

I am using the BlutoothSerial library to connect and send data via my android app to ESP32.
Till now i am able to connect and send some characters to the esp32 but when i try to split that data nothing happens.
I am using the StringSplitter library to split data. I am able to use it with a String that i initialize in my code but couldn’t do that with the data that i got from my phone app.
herer is my code :

void connectBluetooth (){
  String message = "";
  String btInput = "";
  String mySsid;
  if (Serial.available()) {
  if (SerialBT.available()) {
     char incomingChar =;
    if (incomingChar != 'n'){
      message += String(incomingChar);
      message = "error#erreur";
    //Serial.write(incomingChar);  // here i am able to write the data before converting it to String and split it
  btInput += String(incomingChar);
  //writeString(btInput);  // writeString() is a method to print the String value
  StringSplitter *splitter = new StringSplitter(btInput, '#',3);
  int itemCount = splitter->getItemCount();
  for(int i = 0; i < itemCount; i++){
    mySsid = splitter->getItemAtIndex(1);

Source: Windows Questions C++