Audio Focus Request Xamarin Android Audio Player

Introduction

Consider we are creating an audio player application. There may be a chance of creating noisy output on the speaker because another app uses the audio hardware at the same time. To reduce this, Android has a built-in API called AudioFocusRequest.
 
Step 1

We have to register for an audio listener, so that the listener class will provide the information whether another application is using the audio or not.
 
Step 2

Add the following code to the class where you're going to implement the listeners. We have to get the audio service using AudioManger.
  1.  public bool RequestAudioFocus()  
  2.         {  
  3.             var amanager = (AudioManager)GetSystemService(AudioService);  
  4.             AudioFocusRequest audioFocusRequest;  
  5.             if (Build.VERSION.SdkInt > BuildVersionCodes.O)  
  6.             {  
  7.                 audioFocusRequest = amanager.RequestAudioFocus(new AudioFocusRequestClass.Builder(AudioFocus.Gain)  
  8.                                            .SetAudioAttributes(new AudioAttributes.Builder().SetLegacyStreamType(Stream.Music).Build())  
  9.                                            .SetOnAudioFocusChangeListener(this)  
  10.                                            .Build());  
  11.             }  
  12.             else  
  13.             {  
  14.                 audioFocusRequest = amanager.RequestAudioFocus(this, Stream.Music, AudioFocus.Gain);  
  15.             }  
  16.   
  17.             if (audioFocusRequest == AudioFocusRequest.Granted)  
  18.             {  
  19.                 return true;  
  20.             }            
  21.     return false;  
  22. }  
Step 3

Implement the interface "AudioManager.IOnAudioFocusChangeListener"  which implements a method called.

OnAudioFocusChange.   
  1. public void OnAudioFocusChange([GeneratedEnum] AudioFocus focusChange)  
  2. {  
  3. }  
Step 4

Inside "OnAudioFocusChange" Method implement the switch case to handle the audio Focus.
  1. switch (focusChange)  
  2.           {  
  3.               case AudioFocus.Gain:  
  4.   
  5.                 //Gain when other Music Player app releases the audio service
  6.                  
  7.                   }  
  8.                   break;  
  9.               case AudioFocus.Loss:  
  10.                   //We have lost focus stop!  
  11.                     
  12.                   break;  
  13.               case AudioFocus.LossTransient:  
  14.                   //We have lost focus for a short time, but likely to resume so pause  
  15.                  
  16.                   break;  
  17.               case AudioFocus.LossTransientCanDuck:  
  18.                   //We have lost focus but should till play at a muted 10% volume  
  19.                   
  20.                   break;  
  21.           } 
Step 5

The final implemetation will be like below.
  1. public class AudioFocus : AudioManager.IOnAudioFocusChangeListener  
  2. {  
  3.     public AudioFocus()  
  4.     {  
  5.         RequestAudioFocus();  
  6.     }  
  7.     public bool RequestAudioFocus()  
  8.     {  
  9.         audioManager = (AudioManager)GetSystemService(AudioService);  
  10.         AudioFocusRequest audioFocusRequest;  
  11.         if (Build.VERSION.SdkInt > BuildVersionCodes.O)  
  12.         {  
  13.             audioFocusRequest = audioManager.RequestAudioFocus(new AudioFocusRequestClass.Builder(AudioFocus.Gain)  
  14.             .SetAudioAttributes(new AudioAttributes.Builder().SetLegacyStreamType(Stream.Music).Build())              .SetOnAudioFocusChangeListener(this)  
  15.             .Build());  
  16.         }  
  17.         else  
  18.         {  
  19.             audioFocusRequest = audioManager.RequestAudioFocus(this, Stream.Music, AudioFocus.Gain);  
  20.         }  
  21.   
  22.         if (audioFocusRequest == AudioFocusRequest.Granted)  
  23.         {  
  24.             return true;  
  25.         }  
  26.         return false;  
  27.     }  
  28.   
  29.     public void OnAudioFocusChange([GeneratedEnum] AudioFocus focusChange)  
  30.     {  
  31.         switch (focusChange)  
  32.         {  
  33.             case AudioFocus.Gain:  
  34.   
  35.                 //Gain when other Music Player app releases the audio service   
  36.                 break;  
  37.             case AudioFocus.Loss:  
  38.                 //We have lost focus stop!   
  39.   
  40.                 break;  
  41.             case AudioFocus.LossTransient:  
  42.                 //We have lost focus for a short time, but likely to resume so pause   
  43.   
  44.                 break;  
  45.             case AudioFocus.LossTransientCanDuck:  
  46.                 //We have lost focus but should till play at a muted 10% volume   
  47.   
  48.                 break;  
  49.         }  
  50.     }  
  51. }  
At last, remember to release the audio service. 
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