Android SpeechRecognizer problem

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C#

Mobile

Android

speech

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Hi.
I am working on a small application for android using xamarin.android and c#, a part of it is listening to user speech!
I am using Android.Speech.SpeechRecognizer for this.
this is my code :

Android.Speech.SpeechRecognizer sp = Android.Speech.SpeechRecognizer.CreateSpeechRecognizer(this);
            sp.SetRecognitionListener(this);

Intent intent = new Android.Content.Intent(Android.Speech.RecognizerIntent.ActionRecognizeSpeech);
intent.PutExtra(Android.Speech.RecognizerIntent.ExtraLanguageModel, Android.Speech.RecognizerIntent.LanguageModelFreeForm);
intent.PutExtra(Android.Speech.RecognizerIntent.ExtraCallingPackage, "voice.recognition.test");
intent.PutExtra(Android.Speech.RecognizerIntent.ExtraMaxResults, 5); 

sp.BeginningOfSpeech += new EventHandler(sp_BeginningOfSpeech);
sp.ReadyForSpeech += new EventHandler<Android.Speech.ReadyForSpeechEventArgs>(sp_ReadyForSpeech);

button.Click += delegate
{
    sp.StartListening(intent);
};

when i run this, i didnt recieve any event. whats problem?!

thank you for your spent time!