telephonymanager - Android Nougat PhoneStateListener is not triggered

Question

In Android (target 25) I have a background service and in onCreate function I have initialized a phone state listener. It works fine on Android versions that are before Nougat but in Nougat it doesn't work, even though the permissions are granted.

public class Service extends IntentService
{
    class PhoneListener extends PhoneStateListener
    {
       String TAG = getClass().getName();
       @Override
       public void onCallStateChanged(int state, String incomingNumber) 
       {
           super.onCallStateChanged(state, incomingNumber);
           switch (state)
           {
               case TelephonyManager.CALL_STATE_IDLE:
                Log.d(TAG,"IDLE" );
               break;
               case TelephonyManager.CALL_STATE_OFFHOOK:
                Log.d(TAG,"OFFHOOK");
               break;
               case TelephonyManager.CALL_STATE_RINGING:
                Log.d(TAG,"RINGING");
               break;
           }
       }
   }

   public Service ()
   {
       super("ChatService");
   }
   public Service(String name)
   {
       super(name);
   }

   @Override
   public void onCreate()
   {
       super.onCreate();
       TelephonyManager tm = (TelephonyManager)getApplicationContext().getSystemService(TELEPHONY_SERVICE);
       PhoneListener listener = new PhoneListener();
       tm.listen(listener,PhoneStateListener.LISTEN_CALL_STATE);
   }
}

I don't know what is the problem, it looks like the telephony manager is not registered and therefore the onCallStateChanged is not triggered. One of my guesses is the Doze feature that was introduced on Android M, but still.. this code works fine on Android 6 even when the phone is not found "in work"

Answer 1

This was due to a change in PhoneStateListener introduced by https://github.com/aosp-mirror/platform_frameworks_base/commit/f5d7c587e86c64e657a15a12ad70e75d47c48d99#diff-5af2ac899de823cf60597e554bf67fe0.

Local reference to PhoneStateListener is kept track internally only by a weak reference. This makes it eligible for garbage collection upon function exit and once the listener is finalized, apps will not receive any further updates. Solution is to keep a reference to PhoneStateListener via class member variable.