使用带有MVVM和SQLITE数据库的XAMARIN FORMS登录 [英] Login using XAMARIN FORMS with MVVM and SQLITE database

问题描述

我想使用带有MVVM和SQLite数据库的Xamaring表单进行登录。我创建了一个LoginModel.cs，LoginPage.xaml和LoginPage.xaml.cs。 
 
 我的问题是： 
 1.如何创建本地数据库？ 
 2.如何创建，更新，编辑和删除数据到本地数据库？< br /> 
 3.如果用户名和密码类型等于本地数据库中的数据，它如何自动转到主页？ 
 
 
（注意：我的代码在下面）
 LoginPage.xaml（这是我绑定我的条目和按钮的地方）
 
<？xml version =1.0encoding =utf-8？> 
< ContentPage xmlns =http://xamarin.com/schemas/2014/forms
 xmlns：x =http://schemas.microsoft.com/winfx/2009/xaml
x：Class =TBSMobileApplication.View.LoginPage
 BackgroundColor =＃ecf0f1> 
< ContentPage.Content> 
< StackLayout 
 VerticalOptions =StartAndExpand> 
< StackLayout.Padding> 
< OnPlatform 
 x：TypeArguments =Thickness
 iOS =20
 Android =20,100,20,0> 
< / OnPlatform> 
< /StackLayout.Padding> 
 
< Label 
 Text =Username
 TextColor =＃34495e
 Font =Arial，10/> 
< Entry 
 Placeholder =Username
 PlaceholderColor =＃95a5a6
 FontSize =12
 FontFamily =Arial
x：Name =entUsername
 Text ={Binding Username}/> 
< Label 
 Text =Password
 TextColor =＃34495e
 Font =Arial，10/> 
< Entry 
占位符=密码
 PlaceholderColor =＃95a5a6
 FontSize =12
 FontFamily =Arial
 IsPassword = True
x：Name =entPassword
 Text ={Binding Password}/> 
< Button 
 Text =Login
 FontSize =12
 Horizo​​ntalOptions =Start
 BackgroundColor =＃3498db
 Command = {Binding SubmitCommand}/> 
< / StackLayout> 
< /ContentPage.Content> 
< / ContentPage> 
 
 LoginPage.xaml.cs（这是函数执行的地方）
 
 using System; 
使用System.Collections.Generic; 
使用System.Linq; 
使用System.Text; 
使用System.Threading.Tasks; 
使用TBSMobileApplication.Model; 
使用Xamarin.Forms; 
使用Xamarin.Forms.Xaml; 
 
命名空间TBSMobileApplication.View 
 {
 [XamlCompilation（XamlCompilationOptions.Compile）] 
 public partial class LoginPage：ContentPage 
 {
 public UserModel的usermodel; 
 
 public LoginPage（）
 {
 InitializeComponent（）; 
 userModel = new UserModel（）; 
 MessagingCenter.Subscribe< UserModel，string>（此，登录提醒，（发件人，用户名）=> 
 {
 DisplayAlert（，用户名，确定）; 
}）; 
 this.BindingContext = userModel; 
 
 entUsername.Completed + =（object sender，EventArgs e）=> 
 {
 entPassword.Focus（）; 
}; 
 
 entPassword.Completed + =（object sender，EventArgs e）=> 
 {
 userModel.SubmitCommand.Execute（null）; 
}; 
} 
} 
} 
 
 UserModel.cs（这是我获取值和函数的地方）
 
 using System; 
使用System.Collections.Generic;使用System.ComponentModel 
; 
使用System.Text; 
使用System.Windows.Input; 
使用Xamarin.Forms; 
 
 namespace TBSMobileApplication.Model 
 {
 public class UserModel：INotifyPropertyChanged 
 {
 public event PropertyChangedEventHandler PropertyChanged; 
公共字符串用户名; 
 public string用户名
 {
 get {return username; } 
设置
 {
 username = value; 
 PropertyChanged（this，new PropertyChangedEventArgs（Username））; 
} 
} 
 
公共字符串密码; 
公共字符串密码
 {
 get {return password; } 
设置
 {
密码=值; 
 PropertyChanged（这是新的PropertyChangedEventArgs（密码））; 
} 
} 
 
 public ICommand SubmitCommand {get;组; } 
 
 public UserModel（）
 {
 SubmitCommand = new Command（OnSubmit）; 
} 
 
 public void OnSubmit（）
 {
 if（string.IsNullOrEmpty（Username）|| string.IsNullOrEmpty（Password））
 {
 MessagingCenter.Send（这是登录提醒，请填写表格）; 
} 
其他
 {
 MessagingCenter.Send（此处，登录提醒，用户名+&+密码）; 
} 
 
} 
} 
} 

我尝试了什么：

我可以使用** DISPLAYALERT **通过*获取我输入的数据* MessagingCenter **来自文本框。我不知道如何继续创建本地数据库以便能够登录并转到主页面。

解决方案

正在进行快速搜索每个问题应该会给你很多例子。以下是其中一些：



Xamarin登录示例：https：//www.c-sharpcorner.com/article/xamarin-forms-create-a-login -page-mvvm /



官方文档还提供了如何使用本地数据库的快速指南：Xamarin.Forms本地数据库 - Xamarin | Microsoft Docs [ ^ ]

I want to login using Xamaring forms with MVVM and SQLite Database. I created a LoginModel.cs, LoginPage.xaml and LoginPage.xaml.cs.

My Questions are:
1. How can I create a local database?
2. How can I create, updated, edit and delete data to local database?<br/>
3. How can it automatically go to homepage if the username and password type is equal to the data inside the local database?


(Note: my codes are below)
LoginPage.xaml(This is where I bind my entry and button)

    <?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                 x:Class="TBSMobileApplication.View.LoginPage"
                 BackgroundColor="#ecf0f1">
        <ContentPage.Content>
            <StackLayout 
                VerticalOptions="StartAndExpand">
                <StackLayout.Padding>
                    <OnPlatform 
                        x:TypeArguments="Thickness"
                        iOS="20"
                        Android="20,100,20,0">
                    </OnPlatform>
                </StackLayout.Padding>
    
                <Label 
                    Text="Username"
                    TextColor="#34495e"
                    Font="Arial,10"/>
                <Entry
                    Placeholder="Username"
                    PlaceholderColor="#95a5a6"
                    FontSize="12"
                    FontFamily="Arial"
                    x:Name="entUsername"
                    Text="{Binding Username}"/>
                <Label 
                    Text="Password"
                    TextColor="#34495e"
                    Font="Arial,10"/>
                <Entry
                    Placeholder="Password"
                    PlaceholderColor="#95a5a6"
                    FontSize="12"
                    FontFamily="Arial"
                    IsPassword="True"
                    x:Name="entPassword"
                    Text="{Binding Password}"/>
                <Button 
                    Text="Login"
                    FontSize="12"
                    HorizontalOptions="Start"
                    BackgroundColor="#3498db"
                    Command="{Binding SubmitCommand}"/>
            </StackLayout>
        </ContentPage.Content>
    </ContentPage>

LoginPage.xaml.cs (This is where the functions are executed)

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using TBSMobileApplication.Model;
    using Xamarin.Forms;
    using Xamarin.Forms.Xaml;
    
    namespace TBSMobileApplication.View
    {
    	[XamlCompilation(XamlCompilationOptions.Compile)]
    	public partial class LoginPage : ContentPage
    	{
            public UserModel userModel;
    
    		public LoginPage ()
    		{
    			InitializeComponent ();
                userModel = new UserModel();
                MessagingCenter.Subscribe<UserModel, string>(this,"Login Alert",(sender, username) =>
                {
                    DisplayAlert("", username, "Ok");
                });
                this.BindingContext = userModel;
    
                entUsername.Completed += (object sender, EventArgs e) =>
                {
                    entPassword.Focus();
                };
    
                entPassword.Completed += (object sender, EventArgs e) =>
                {
                    userModel.SubmitCommand.Execute(null);
                };
    		}
    	}
    }

UserModel.cs(This is where I get the values and functions)

    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Text;
    using System.Windows.Input;
    using Xamarin.Forms;
    
    namespace TBSMobileApplication.Model
    {
        public class UserModel : INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            public string username;
            public string Username
            {
                get { return username; }
                set
                {
                    username = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("Username"));
                }
            }
    
            public string password;
            public string Password
            {
                get { return password; }
                set
                {
                    password = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("Password"));
                }
            }
    
            public ICommand SubmitCommand { get; set; }
    
            public UserModel()
            {
                SubmitCommand = new Command(OnSubmit);
            }
    
            public void OnSubmit()
            {
                if (string.IsNullOrEmpty(Username) || string.IsNullOrEmpty(Password))
                {
                    MessagingCenter.Send(this, "Login Alert", "Please fill-up the form");
                }
                else
                {
                    MessagingCenter.Send(this, "Login Alert", Username + " & " + Password);
                }
    
            }
        }
    }

What I have tried:

I can get the data I typed using a "**DISPLAYALERT**" through "**MessagingCenter**" from the text box. I don't know how to proceed in creating a local database to be able to login and go to the main page.

解决方案

Doing a quick search for each of your question should give you a lot of examples. Here are a few of them:

Xamarin Login Example: https://www.c-sharpcorner.com/article/xamarin-forms-create-a-login-page-mvvm/

The official documenation also has a quick guide on how to use Local database: Xamarin.Forms Local Databases - Xamarin | Microsoft Docs[^]

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