title: Xamarin: How to deal with an ACTION_ANSWER Activity
body: <p>I tried to deal with incoming calls to cancel or answer it but I can't.
  I tried the following code:</p>
  
  <pre><code>[BroadcastReceiver(Label = "Blocking Calls")]
  [IntentFilter(new string[] { "android.intent.action.PHONE_STATE" })]
  public class MyReceiver : Android.Content.BroadcastReceiver
  {
      private const string IntentAction_BlockingCalls = "android.intent.action.PHONE_STATE";
  
      public override void OnReceive(Context context, Intent intent)
      {
          if (intent.Action == IntentAction_BlockingCalls)
          {
              // ensure there is information
              if (intent.Extras != null)
              {
                  // get the incoming call state
                  string state = intent.GetStringExtra(TelephonyManager.ExtraState);
  
                  // check the current state
                  if (state == TelephonyManager.ExtraStateRinging)
                  {
                      // read the incoming call telephone number
                      string telephoneNumber = intent.GetStringExtra(TelephonyManager.ExtraIncomingNumber);
  
                      Intent buttonDown = new Intent(Intent.ActionMediaButton);
                      buttonDown.PutExtra(Intent.ActionView, new KeyEvent(KeyEventActions.Down, Keycode.Headsethook));
                      context.SendBroadcast(buttonDown);
  
                      Toast.MakeText(context, telephoneNumber, ToastLength.Short).Show();  // Flag 4        
                      // check the read telephone
                      if (string.IsNullOrEmpty(telephoneNumber))
                          telephoneNumber = string.Empty;
                  }
                  else if (state == TelephonyManager.ExtraStateOffhook)
                  {
                      // Toast.MakeText(context, "The call is answered", ToastLength.Short).Show();  // Flag 5
                      // incoming call answer
                  }
                  else if (state == TelephonyManager.ExtraStateIdle)
                  {
                      // Toast.MakeText(context, "The call have ended", ToastLength.Short).Show();  // Flag 6
                      // incoming call end
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>I fetch the incoming phone number successfully but I can't answer or cancel it.So, I tried to use the action (<code>ActionAnswer</code>) below</p>
  
  <pre><code>Intent A = new Intent(Intent.ActionAnswer);
  </code></pre>
  
  <p>And as it's appearing in this screen shot from android developer site 
  <a href="https://i.stack.imgur.com/fwM4s.png" rel="nofollow noreferrer">image</a>
  the output and the input are nothing!!!. 
  How can I deal with that action? or there are any other methods I can use to cancel the incoming calls?
  Thanks for advise.
  Here is the link of android developer.
  <a href="https://developer.android.com/reference/android/content/Intent.html#ACTION_ANSWER" rel="nofollow noreferrer">https://developer.android.com/reference/android/content/Intent.html#ACTION_ANSWER</a></p>