如何在 xamarin 表单中获得更多输入？
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【中文标题】如何在 xamarin 表单中获得更多输入？【英文标题】：How to getUser with more input in xamarin forms? 【发布时间】：2020-08-28 23:34:01 【问题描述】：我正在使用firebase RealTimeDataBase，我也想使用名称（GetUser（字符串电子邮件，字符串名称））来获取用户，那么我如何修改最后一个查询来做到这一点？ 因为当我注册时我成功地看到了名字，但是当我登录时我没有看到名字，但是电子邮件是的
用户由组成：电子邮件、姓名、类别、密码
代码：
FirebaseHelper.cs
namespace yourActivity.ViewModel
public class FirebaseHelper
public static byte[] GetHash(string inputString)
using (HashAlgorithm algorithm = SHA256.Create())
return algorithm.ComputeHash(Encoding.UTF8.GetBytes(inputString));
public static string GetHashString(string inputString)
StringBuilder sb = new StringBuilder();
foreach (byte b in GetHash(inputString))
sb.Append(b.ToString("X2"));
return sb.ToString();
public static FirebaseClient firebase = new
FirebaseClient("https://youractivity-5acac.firebaseio.com/");
//Read All
public static async Task<List<Users>> GetAllUser()
try
var userlist = (await firebase
.Child("Users")
.OnceAsync<Users>()).Select(item =>
new Users
Email = item.Object.Email,
Password = item.Object.Password,
Nome = item.Object.Nome,
Categoria = item.Object.Categoria
).ToList();
return userlist;
catch (Exception e)
Debug.WriteLine($"Error:e");
return null;
//Read
public static async Task<Users> GetUser(string email)
try
var allUsers = await GetAllUser();
await firebase
.Child("Users")
.OnceAsync<Users>();
return allUsers.Where(a => a.Email == email).FirstOrDefault();
catch (Exception e)
Debug.WriteLine($"Error:e");
return null;
//Insert a user
public static async Task<bool> AddUser(string email, string password, string nome, string categoria)
try
await firebase
.Child("Users")
.PostAsync(new Users() Email = email, Password = GetHashString(password), Nome = nome, Categoria = categoria);
return true;
catch (Exception e)
Debug.WriteLine($"Error:e");
return false;
//Update
public static async Task<bool> UpdateUser(string email, string password, string nome, string categoria)
try
var toUpdateUser = (await firebase
.Child("Users")
.OnceAsync<Users>()).Where(a => a.Object.Email == email).FirstOrDefault();
await firebase
.Child("Users")
.Child(toUpdateUser.Key)
.PutAsync(new Users() Email = email, Password = GetHashString(password) , Nome = nome, Categoria = categoria);
return true;
catch (Exception e)
Debug.WriteLine($"Error:e");
return false;
//Delete User
public static async Task<bool> DeleteUser(string email)
try
var toDeletePerson = (await firebase
.Child("Users")
.OnceAsync<Users>()).Where(a => a.Object.Email == email).FirstOrDefault();
await firebase.Child("Users").Child(toDeletePerson.Key).DeleteAsync();
return true;
catch (Exception e)
Debug.WriteLine($"Error:e");
return false;
SignupPage.xaml.cs
namespace yourActivity.View
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class SignupPage : ContentPage
SignupViewModel signUpVM;
public SignupPage()
InitializeComponent();
signUpVM = new SignupViewModel();
//set binding
BindingContext = signUpVM;
SignupViewModel.cs
namespace yourActivity.ViewModel
public class SignupViewModel : INotifyPropertyChanged
private string email;
public string Email
get return email;
set
email = value;
PropertyChanged(this, new PropertyChangedEventArgs("Email"));
private string nome;
public string Nome
get return nome;
set
nome = value;
PropertyChanged(this, new PropertyChangedEventArgs("Nome"));
private string categoria;
public string Categoria
get return categoria;
set
categoria = value;
PropertyChanged(this, new
PropertyChangedEventArgs("Categoria"));
private string password;
public event PropertyChangedEventHandler PropertyChanged;
public string Password
get return password;
set
password = value;
PropertyChanged(this, new
PropertyChangedEventArgs("Password"));
private string confirmpassword;
public string ConfirmPassword
get return confirmpassword;
set
confirmpassword = value;
PropertyChanged(this, new
PropertyChangedEventArgs("ConfirmPassword"));
public Command SignUpCommand
get
return new Command(() =>
if (Password == ConfirmPassword)
SignUp();
else
App.Current.MainPage.DisplayAlert("", "Password must be same as above!", "OK");
);
private async void SignUp()
//null or empty field validation, check weather email and password is null or empty
if (string.IsNullOrEmpty(Email) || string.IsNullOrEmpty(Password) || string.IsNullOrEmpty(Nome) || string.IsNullOrEmpty(Categoria))
await App.Current.MainPage.DisplayAlert("Empty Values", "Please enter all the values", "OK");
else
//call AddUser function which we define in Firebase helper class
var user = await FirebaseHelper.AddUser(Email, Password, Nome, Categoria);
//AddUser return true if data insert successfuly
if (user)
await App.Current.MainPage.DisplayAlert("SignUp Success", "", "Ok");
//Navigate to Wellcom page after successfuly SignUp
//pass user email to welcom page
await App.Current.MainPage.Navigation.PushAsync(new TabbedPage1(email, nome));
else
await App.Current.MainPage.DisplayAlert("Error", "SignUp Fail", "OK");
LoginPage.xaml.cs
namespace yourActivity.View
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class LoginPage : ContentPage
LoginViewModel loginViewModel;
public LoginPage()
loginViewModel = new LoginViewModel();
InitializeComponent();
BindingContext = loginViewModel;
LoginViewModel.cs
namespace yourActivity.ViewModel
public class LoginViewModel : INotifyPropertyChanged
public static byte[] GetHash(string inputString)
using (HashAlgorithm algorithm = SHA256.Create())
return algorithm.ComputeHash(Encoding.UTF8.GetBytes(inputString));
public static string GetHashString(string inputString)
StringBuilder sb = new StringBuilder();
foreach (byte b in GetHash(inputString))
sb.Append(b.ToString("X2"));
return sb.ToString();
private string email;
public string Email
get return email;
set
email = value;
PropertyChanged(this, new PropertyChangedEventArgs("Email"));
private string nome;
public string Nome
get return nome;
set
nome = value;
PropertyChanged(this, new PropertyChangedEventArgs("Nome"));
private string password;
public event PropertyChangedEventHandler PropertyChanged;
public string Password
get return password;
set
password = value;
PropertyChanged(this, new PropertyChangedEventArgs("Password"));
public Command LoginCommand
get
return new Command(Login);
public Command SignUp
get
return new Command(() => App.Current.MainPage.Navigation.PushAsync(new SignupPage()); );
private async void Login()
//null or empty field validation, check weather email and password is null or empty
if (string.IsNullOrEmpty(Email) || string.IsNullOrEmpty(Password))
await App.Current.MainPage.DisplayAlert("Empty Values", "Please enter Email and Password", "OK");
else
//call GetUser function which we define in Firebase helper class
var user = await FirebaseHelper.GetUser(Email);
//firebase return null valuse if user data not found in database
if (user != null)
if (Email == user.Email && GetHashString(Password) == user.Password)
await App.Current.MainPage.DisplayAlert("Login Success", "", "Ok");
//Navigate to Wellcom page after successfuly login
//pass user email to welcom page
await App.Current.MainPage.Navigation.PushAsync(new TabbedPage1(email, nome));
else
await App.Current.MainPage.DisplayAlert("Login Fail", "Please enter correct Email and Password", "OK");
else
await App.Current.MainPage.DisplayAlert("Login Fail", "User not found", "OK");
TabbedPage1.xaml.cs
namespace yourActivity
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class TabbedPage1 : TabbedPage
TabbedPage1ViewModel TabbedPageVM;
readonly FirebaseHelper firebaseHelper = new FirebaseHelper();
public TabbedPage1(string email, string nome)
InitializeComponent();
TabbedPageVM = new TabbedPage1ViewModel(email, nome);
BindingContext = TabbedPageVM;
TabbedPage1ViewModel
namespace yourActivity.ViewModel
public class TabbedPage1ViewModel : INotifyPropertyChanged
public TabbedPage1ViewModel(string email2, string nome2)
Email = email2;
Nome = nome2;
private string email;
public string Email
get return email;
set email = value;
private string nome;
public string Nome
get return nome;
set nome = value;
private string categoria;
public string Categoria
get return categoria;
set categoria = value;
private string password;
public event PropertyChangedEventHandler PropertyChanged;
public string Password
get return password;
set
password = value;
PropertyChanged(this, new PropertyChangedEventArgs("Password"));
public Command UpdateCommand
get return new Command(Update);
public Command DeleteCommand
get return new Command(Delete);
//For Logout
public Command LogoutCommand
get
return new Command(() =>
App.Current.MainPage.Navigation.PushAsync(new LoginPage());
);
//Update user data
private async void Update()
try
if (!string.IsNullOrEmpty(Password))
var isupdate = await FirebaseHelper.UpdateUser(Email, Password, Nome, Categoria);
if (isupdate)
await App.Current.MainPage.DisplayAlert("Update Success", "", "Ok");
else
await App.Current.MainPage.DisplayAlert("Error", "Record not update", "Ok");
else
await App.Current.MainPage.DisplayAlert("Password Require", "Please Enter your password", "Ok");
catch (Exception e)
Debug.WriteLine($"Error:e");
//Delete user data
private async void Delete()
try
var isdelete = await FirebaseHelper.DeleteUser(Email);
if (isdelete)
await App.Current.MainPage.Navigation.PopAsync();
else
await App.Current.MainPage.DisplayAlert("Error", "Record not delete", "Ok");
catch (Exception e)
Debug.WriteLine($"Error:e");
【问题讨论】：
【参考方案1】：您可以使用 if 语句来决定使用email 或name 来查询用户：
//Read
public static async Task<Users> GetUser(string email = null, string name = null)
try
var allUsers = await GetAllUser();
await firebase
.Child("Users")
.OnceAsync<Users>();
if (email != null && email.Length> 0)
return allUsers.Where(a => a.Email == email).FirstOrDefault();
return allUsers.Where(a => a.Name == name).FirstOrDefault();
catch (Exception e)
Debug.WriteLine($"Error:e");
return null;
【讨论】：
对不起，我没有看到问题中的更新。哪个部分不适用于您的问题？你能澄清一下吗？ 我尝试添加这些 linea 但在登录时我无法看到名称 在代码中，如果无法可视化名称，则可以传递正确的电子邮件，名称等于null，然后它将返回allUsers.Where(a => a.Email == email).FirstOrDefault();。我用默认值的名称和电子邮件更新了我的答案。
这里不工作是什么意思？你有任何例外或其他什么吗？你能补充更详细的信息吗？以上是关于如何在 xamarin 表单中获得更多输入？的主要内容，如果未能解决你的问题，请参考以下文章
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