use 2 different SpeechRecognition in one class is not working !!

[itfuturz2020]

i am not able to use 2 different SpeechRecognition in one class. when i initialize both SpeechRecognition like -
_speechRecognition1= new SpeechRecognition();
_speechRecognition2 = new SpeechRecognition(); and when i set setRecognitionResultHandler to both variable , it is override _speechRecognition1 with _speechRecognition2 ...
why ?
if anyone understand my problem , then please give me solution !
thank you

[rodolZ80]

The SpeechRecognition is a Singleton

  static final SpeechRecognition _speech = new SpeechRecognition._internal();
  factory SpeechRecognition() => _speech;
  SpeechRecognition._internal() {
    _channel.setMethodCallHandler(_platformCallHandler);
  }