I need to update the data The code is down bellow

Question

I have to extract the data from a realtime database on firebase. I handle to extract it once with the code down bellow, but I don't know how to do manage to extract it when data on firebase is changed.

public static async Task<List<SensorsData>> GetDate()
        {
          return (await client.Child("Parking").OnceAsync<SensorsData>()).Select(item => new SensorsData{
              available = item.Object.available,
              slot1 = item.Object.slot1,
              slot2 = item.Object.slot2,
              }).ToList();

        }



        public static async Task<SensorsData> GetRomana()
        {
            try
            {
                var response = await GetDate();
                await client.Child("Parking").OnceAsync<SensorsData>();
                return response.First();
            }
            catch(Exception e)
            {
                Debug.WriteLine($"Error:{e}");
                return null;
            }

        }

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

If you use FirebaseDatabase.net nugget package, this package do not provide any event to monitor the data change in the DB.

Then I find the native android have ValueEventListener, So you can use this Xamarin.Firebase.Database package in xamarin android.

   public class MyValueEventListener : Java.Lang.Object, IValueEventListener  
       {  
     
           public void OnCancelled(DatabaseError error)  
           {  
              // throw new NotImplementedException();  
           }  
     
           public void OnDataChange(DataSnapshot snapshot)  
           {  
              // throw new NotImplementedException();  
           }  
     
       }  

Then Add the data change event: DatabaseReference databaseReference = FirebaseDatabase.Instance.Reference; databaseReference.Child(Constants.ARG_CHAT_ROOMS).Ref.AddListenerForSingleValueEvent(new MyValueEventListener())

Here is an similar thread:

https://stackoverflow.com/questions/42499066/how-to-use-interface-ivalueeventlistener-in-object-databasereference-xamarin-fir

Best Regards,

Leon Lu

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