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