android:id="@+id/main_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/Background2"
android:orientation="vertical"
android:weightSum="4">
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="3"
    android:gravity="center_horizontal"
    android:orientation="vertical">
    <ImageView
        android:id="@+id/icon"
        style="@style/ThemeOverlay.FirebaseIcon"
        android:contentDescription="@string/desc_firebase_lockup"
        android:src="@drawable/firebase_lockup_400"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="@string/sign_out"
        android:theme="@style/ThemeOverlay.MyDarkButton"
        android:visibility="gone"
        android:id="@+id/button1" />
    <TextView
        android:id="@+id/title_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/title_bottom_margin"
        android:text="@string/facebook_title_text"
        android:theme="@style/ThemeOverlay.MyTitleText" />
    <TextView
        android:id="@+id/status"
        style="@style/ThemeOverlay.MyTextDetail"
        android:text="@string/signed_out" />
    <TextView
        android:id="@+id/detail"
        style="@style/ThemeOverlay.MyTextDetail"
        tools:text="Firebase User ID: 123456789abc" />
<TextView
    android:text="First Name"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/TxtFirstname"
    android:layout_centerHorizontal="true"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="20dp" />
<TextView
    android:text="Last Name"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/TxtLastName"
    android:layout_centerHorizontal="true"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="10dp" />
<TextView
    android:text="User Name"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/TxtName"
    android:layout_centerHorizontal="true"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="10dp" />
</LinearLayout>
<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:background="@color/grey_300">
    <com.facebook.login.widget.LoginButton
        android:id="@+id/button_facebook_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true" />
  <com.facebook.login.widget.ProfilePictureView
    android:id="@+id/ImgPro"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:layout_marginTop="20dp"
    android:layout_gravity="center_horizontal" />
     <Button
        android:id="@+id/button_facebook_signout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="@string/sign_out"
        android:theme="@style/ThemeOverlay.MyDarkButton"
        android:visibility="gone" />
</RelativeLayout>

mprofileTracker = new MyProfileTracker();
        mprofileTracker.mOnProfileChanged += FirebaseUser;
        mprofileTracker.StartTracking();
        SetContentView(Resource.Layout.activity_facebook);
        var button1 = FindViewById<Button>(Resource.Id.button1);

        // Views
        TxtFirstName = FindViewById<TextView>(Resource.Id.TxtFirstname);
        TxtLastName = FindViewById<TextView>(Resource.Id.TxtLastName);
        TxtName = FindViewById<TextView>(Resource.Id.TxtName);
        mprofilepic = FindViewById<ProfilePictureView>(Resource.Id.ImgPro);
        mStatusTextView = FindViewById<TextView>(Resource.Id.status);
        mDetailTextView = FindViewById<TextView>(Resource.Id.detail);
        // Button listeners
        FirebaseApp.InitializeApp(this);
        mAuth = FirebaseAuth.Instance;
     //   mprofilepic = FindViewById<ProfilePictureView>(Resource.Id.ImgPro);
        LoginButton fblogin = FindViewById<LoginButton>(Resource.Id.button_facebook_login);
        fblogin.Click += delegate
        {
            mCallbackManager = CallbackManagerFactory.Create();
            fblogin.RegisterCallback(mCallbackManager, this);

        };

        FindViewById(Resource.Id.button_facebook_signout).Click += delegate
        {
            SignOut();
        };
    }
    void FirebaseUser(object sender, OnFirebaseChangedEventArgs e)
    {
        if (e.FirebaseUser != null)
        {
            try
            {
                TxtFirstName.Text = e.FirebaseUser.FirstName;
                TxtLastName.Text = e.FirebaseUser.LastName;
                TxtName.Text = e.FirebaseUser.Name;
                mprofilepic.ProfileId = e.FirebaseUser.Id;
            }
            catch (Java.Lang.Exception ex)
            {

            }
        }

        else
        {
            TxtFirstName.Text = "First Name";
            TxtLastName.Text = "Last Name";
            TxtName.Text = "Name";
            mprofilepic.ProfileId = null;
        }
    }


    void AuthStateChanged(object sender, FirebaseAuth.AuthStateEventArgs e)
    {
        var user = e.Auth.CurrentUser;
        if (user != null)
        {
            // User is signed in
            Android.Util.Log.Debug(TAG, "onAuthStateChanged:signed_in:" + user.Uid);
        }
        else
        {
            // User is signed out
            Android.Util.Log.Debug(TAG, "onAuthStateChanged:signed_out");
        }
        // [START_EXCLUDE]

        // [END_EXCLUDE]
    }

    // [START on_start_add_listener]
    protected override void OnStart()
    {
        base.OnStart();
        mAuth.AuthState += AuthStateChanged;
    }
    // [END on_start_add_listener]

    //[START on_stop_remove_listener]
    protected override void OnStop()
    {
        base.OnStop();
        mAuth.AuthState -= AuthStateChanged;
    }
    // [END on_stop_remove_listener]
    protected override void OnActivityResult(int requestCode, [GeneratedEnum] Result resultCode, Intent data)
    {
        base.OnActivityResult(requestCode, resultCode, data);
        var resultCodeNum = 0;
        switch (resultCode)
        {
            case Result.Ok:
                resultCodeNum = -1;
                break;

            case Result.Canceled:
                resultCodeNum = 0;
                break;

            case Result.FirstUser:
                resultCodeNum = 1;
                break;
        }
        mCallbackManager.OnActivityResult(requestCode, resultCodeNum, data);
    }


    private void handleFacebookAccessToken(AccessToken accessToken)
    {

        AuthCredential credential = FacebookAuthProvider.GetCredential(accessToken.Token);
        mAuth.SignInWithCredential(credential).AddOnCompleteListener(this, this);
    }
    private void SignOut()
    {
        // Firebase sign out
        mAuth.SignOut();


    }


    public void OnCancel()
    {

    }



    public void OnError(FacebookException error)
    {
        throw new NotImplementedException();
    }

    public void OnSuccess(Java.Lang.Object result)
    {
        LoginResult loginResult = result as LoginResult;
        handleFacebookAccessToken(loginResult.AccessToken);
    }

    public void OnComplete(Android.Gms.Tasks.Task task)
    {
        if (task.IsSuccessful)
        {
            FirebaseUser user = mAuth.CurrentUser;
        }
        else
        {
            Toast.MakeText(this, "Authentication failed.", ToastLength.Short).Show();
        }

    }

    public void OnCompleted(Org.Json.JSONObject json, GraphResponse response)
    {
        string data = json.ToString();
        FacebookResult result = JsonConvert.DeserializeObject<FacebookResult>(data);
    }

    public class MyProfileTracker : ProfileTracker
    {
        public event EventHandler<OnFirebaseChangedEventArgs> mOnProfileChanged;

        protected override void OnCurrentProfileChanged(Profile oldProfile, Profile newProfile)
        {
            if (mOnProfileChanged != null)
            {
                mOnProfileChanged.Invoke(this, new OnFirebaseChangedEventArgs(newProfile));
            }
        }
    }
    public class OnFirebaseChangedEventArgs : EventArgs
    {
        public Profile FirebaseUser;

        public OnFirebaseChangedEventArgs(Profile profile) { FirebaseUser = profile; }
    }
}