How to retrieve data from firebase database into xamarin android app

Shehrii

I am trying to retrieve data from firebase. But, i couldn't find a method to retrieve data from firebase database. Now i am out of ideas please help me.

jezh

I have developed a chat app by FireBase ,and it works well.
The Object I used to comunicated with FireBase Server is as follows:

  class FriendlyMessage : Java.Lang.Object, IParcelable
   {
    public String text;
    public String name;
    public String photoUrl;
    public String UId;
     public FriendlyMessage(String text, String name, String photoUrl)
    {
        this.text = text;
        this.name = name;
        this.photoUrl = photoUrl;
        this.UId = Guid.NewGuid().ToString();
    }

     public static HashMap MsgModelToMap(FriendlyMessage msg)
    {
        HashMap map = new HashMap();

        map.Put("text", msg.text);
        map.Put("name", msg.name);
        map.Put("photoUrl", msg.photoUrl);
        map.Put("UId", msg.UId);

        return map;
    }

    public static FriendlyMessage MapToMsgModel(DataSnapshot snapShot)
    {
        FriendlyMessage msg = new FriendlyMessage();

        if (snapShot.GetValue(true) == null)
        {
            return null;
        }

        msg.UId = snapShot.Key;
        msg.text = snapShot.Child("text")?.GetValue(true)?.ToString();
        msg.name = snapShot.Child("name")?.GetValue(true)?.ToString();
        msg.photoUrl = snapShot.Child("photoUrl")?.GetValue(true)?.ToString();

        return msg;

    }
    //............
  }

The first three fields are stored in Database as follows:

The main code to communicate with FireBase database is as follows :
1. send message to FireBase database

  public class MainActivity : AppCompatActivity,IOnClickListener,IOnSuccessListener
{
    public static readonly String ANONYMOUS = "anonymous";
    public static readonly int DEFAULT_MSG_LENGTH_LIMIT = 1000;
    public static readonly int RB_SIGNED_IN = 1;
    private static readonly int RC_PHOTO_PICKER = 2;

    private ListView mMessageListView;
    private static MessageAdapter mMessageAdapter;
    private ProgressBar mProgressBar;
    private ImageButton mPhotoPickerButton;
    private EditText mMessageEditText;
    private Button mSendButton;

    private String mUsername;

    private FirebaseDatabase mFirebaseDatabase;
    private DatabaseReference mMsgDatabaseReference;
    private IChildEventListener mChildEventListener;

    //********************************************************************
    private FirebaseStorage mFirebaseStorage;
    private StorageReference mChatPhotosStorageRef;
    //********************************************************************
    private FirebaseAuth auth;
    //private FirebaseAuth.IAuthStateListener authStateListener;

    private static string mUserName = "";

   static List<FriendlyMessage> msgList = new List<FriendlyMessage>();

    //private TextView msgText;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        SetContentView(Resource.Layout.activity_main);
        //my chat app code
        IsPlayServicesAvailable();
     //...............
        mPhotoPickerButton = FindViewById<ImageButton>(Resource.Id.photoPickerButton);
        mMessageEditText = FindViewById<EditText>(Resource.Id.messageEditText);
        mSendButton = FindViewById<Button>(Resource.Id.sendButton);

        mPhotoPickerButton.SetOnClickListener(this);

        mUsername = ANONYMOUS;
        mFirebaseDatabase = FirebaseDatabase.Instance;
        mFirebaseStorage = FirebaseStorage.Instance;
        mMsgDatabaseReference = mFirebaseDatabase.Reference.Child("messages");
        mChatPhotosStorageRef = mFirebaseStorage.Reference.Child("chat_photos");

        //mFirebaseAuth = FirebaseAuth.Instance;
        auth = FirebaseAuth.GetInstance(LoginActivity.app);
        //authStateListener = new AuthStateListener(this);
        if (auth.CurrentUser != null)
        {
            mUserName = auth.CurrentUser.Email;
        }


        // Initialize progress bar
        mProgressBar.Visibility = Android.Views.ViewStates.Invisible;
        mSendButton.Click += delegate {
            // TODO: Send messages on click
            FriendlyMessage friendlyMessage = new FriendlyMessage(mMessageEditText.Text, mUsername, null);
            //Java.Lang.Object obj = Java.Lang.Class.FromType(typeof(FriendlyMessage));
            mMsgDatabaseReference.Push().SetValue(FriendlyMessage.MsgModelToMap(friendlyMessage));
            // Clear input box
            mMessageEditText.Text="";

        };
        attachDataBaseReadListener();

//......................

    }     

2. method attachDataBaseReadListener :

   private void attachDataBaseReadListener() {
        if (mChildEventListener == null) { 
        mChildEventListener = new ChildMsgEventListener();
        mMsgDatabaseReference.AddChildEventListener(mChildEventListener);
        }
    }

 private class ChildMsgEventListener : Java.Lang.Object, IChildEventListener
    {
        public void OnCancelled(DatabaseError error)
        {
            throw new NotImplementedException();
        }

   // when added the item , you can retrieve the data from the database
        public void OnChildAdded(DataSnapshot snapshot, string previousChildName)
        {
            var obj = snapshot.Children;
            foreach (DataSnapshot s in obj.ToEnumerable())
            {
                var model = FriendlyMessage.MapToMsgModel(snapshot);

                if (model != null && !IsExisting(model)) {
                    Log.Debug(TAG,"current model = " + model.ToString());
                    msgList.Add(model);
                }
            }
           mMessageAdapter.NotifyDataSetChanged();
        }
        public void OnChildChanged(DataSnapshot snapshot, string previousChildName)
        {
            throw new NotImplementedException();
        }
        public void OnChildMoved(DataSnapshot snapshot, string previousChildName)
        {
            throw new NotImplementedException();
        }
        public void OnChildRemoved(DataSnapshot snapshot)
        {
            throw new NotImplementedException();
        }
    }

jezh

Have you got your solution at last?

aqasyarahimi

Can you provide the full code

aqasyarahimi

Including the class name

KeesPaul

Thanks, this really helped me in using firebase realtime database in contrast to other information found on the internet.