public partial class LoginPage : TabbedPage
    {
        public LoginPage()
        {
            InitializeComponent();
            NavigationPage.SetHasNavigationBar(this, false);

        }

        protected async void btnLogin_Clicked(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(emailEntry.Text))
            {
                await DisplayAlert("Erro", "Digite um usuário válido", "Aceitar");
                emailEntry.Focus();
                return;
            }

            if (string.IsNullOrEmpty(senhaEntry.Text))
            {
                await DisplayAlert("Erro", "Digite uma senha", "Aceitar");
                senhaEntry.Focus();
                return;
            }

            try
            {
                waitActivityIndicator.IsRunning = true;
                var loginRequest = new Login
                {
                    UserName = emailEntry.Text,
                    Password = senhaEntry.Text,
                };

                //invocar serviço


                waitActivityIndicator.IsRunning = false;
                Device.BeginInvokeOnMainThread(() => App.Current.MainPage = new MainPageRoot());
            }
            catch (Exception ex)
            {
                waitActivityIndicator.IsRunning = false;

                await DisplayAlert("Erro", "Usuário ou Senha Incorretos", "Aceitar");
            }
        }

    }

public async void Logar(Login login)
        {



            var jsonRequest = JsonConvert.SerializeObject(login);
            var httpContent = new StringContent(jsonRequest, Encoding.UTF8, "application/json");
            var resp = string.Empty;

            try
            {
                var client = new HttpClient();
                client.BaseAddress = new Uri($"{BaseAddress}/_signin.php?usuario={login.UserName}&senha={login.Password}");
                var url = "";
                var result = await client.PostAsync(url, httpContent);

                if (!result.IsSuccessStatusCode)
                {
                    throw new Exception(result.RequestMessage.Content.ToString());
                }

                resp = await result.Content.ReadAsStringAsync();
                //verificar resposta do ws
                var user = JsonConvert.DeserializeObject<Colaborador>(resp);



            }
            catch (Exception)
            {
                throw;

            }

        }