保持用户登录xamarin.forms应用程序，除非单击注销

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我正在为我的应用程序使用xamarin.forms。它允许用户通过Facebook登录。我在应用程序中添加了一个注销按钮，以简单地导航回到登录页面，但是我注意到，当我退出我的应用程序而不按注销按钮时，该应用程序将在登录页面恢复(导致用户每次都不断输入其登录详细信息他们必须重新打开该应用程序)。关闭并重新打开应用程序后，如何保持用户登录状态？任何指导对此将不胜感激。

App.cs(MainPage是我的登录页面)

public App()
{
InitializeComponent();
MainPage = new NavigationPage(new MainPage());
}

public async static Task NavigateToSMS()
{
await App.Current.MainPage.Navigation.PushAsync(new SMS());
}

public static void NavigateToProfile()
{
App.Current.MainPage = (new InvalidLogin());
}
public static void NavigateToVerified()
{
App.Current.MainPage = (new Profile());
}

protected override void OnStart()
{
// Handle when your app starts
}

protected override void OnSleep()
{
// Handle when your app sleeps
}

protected override void OnResume()
{
// Handle when your app sleeps
}

Facebook渲染

[assembly: ExportRenderer(typeof(Login), typeof(LoyaltyWorx.Droid.FacebookRender))]
namespace LoyaltyWorx.Droid
{

public class FacebookRender : PageRenderer
{
public FacebookRender()
{

String error;
var activity = this.Context as Activity;

var auth = new OAuth2Authenticator(
clientId:"",
scope:"email",
authorizeUrl: new Uri("https://www.facebook.com/dialog/oauth/"),
redirectUrl: new Uri("https://www.facebook.com/connect/login_success.html")
);

auth.Completed += async (sender, eventArgs) =>
{
try
{
if (eventArgs.IsAuthenticated)
{
await AccountStore.Create().SaveAsync(eventArgs.Account,"FacebookProviderKey");

var accessToken = eventArgs.Account.Properties["access_token"].ToString();
var expiresIn = Convert.ToDouble(eventArgs.Account.Properties["expires_in"]);
var expiryDate = DateTime.Now + TimeSpan.FromSeconds(expiresIn);

var request = new OAuth2Request("GET", new Uri("https://graph.facebook.com/me?fields=email,first_name,last_name,gender,picture"), null, eventArgs.Account);
var response = await request.GetResponseAsync();
var obj = JObject.Parse(response.GetResponseText());

var id = obj["id"].ToString().Replace(""","");
var name = obj["first_name"].ToString().Replace(""","");
var surname = obj["last_name"].ToString().Replace(""","");
var gender = obj["gender"].ToString().Replace(""","");
var email = obj["email"].ToString().Replace(""","");

Customer.Customers cust = new Customer.Customers();
cust.Number ="";
cust.Name = name;
cust.Surname = surname;
cust.Address ="sample";
cust.Email = email;
cust.City ="DBN";
cust.Region ="KZN";
cust.Country ="SA";
cust.MobilePhone ="";
cust.DOB = DateTime.Now;
cust.Phone ="";
cust.Credentials = new Customer.Credentials();
cust.Credentials.Authenticated = true;
cust.Credentials.SecretKey ="73fnfdbjfdj";
cust.DeviceToken = GcmService.RegistrationID;

CustomerService service = new CustomerService();
Settings.Token = await service.AddCustomer(cust);
if (Settings.MobileNo == null || Settings.MobileNo =="")
{
await App.NavigateToSMS();

}
else
{
App.NavigateToVerified();
}
}
else
{
App.NavigateToProfile();
}
}
catch(Exception ex)
{
error = ex.Message;
}
};
activity.StartActivity(auth.GetUI(activity));
}

}
}

用户登录后出现的页面

namespace LoyaltyWorx
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Profile : MasterDetailPage
{
public List<MasterPageItem> menuList { get; set; }
public Profile()
{
InitializeComponent();
this.lblMessage.Text = Settings.Name +"" + Settings.Surname;
menuList = new List<MasterPageItem>();
var page1 = new MasterPageItem() { Title ="Home", Icon ="home.png", TargetType = typeof(Page1) };
var page2 = new MasterPageItem() { Title ="Cards", Icon ="card.png", TargetType = typeof(Cards) };
var page3 = new MasterPageItem() { Title ="Transactions", Icon ="settings.png", TargetType = typeof(Transactions) };
var page4 = new MasterPageItem() { Title ="My Profile", Icon ="profile.png", TargetType = typeof(UpdateProfile) };
var page5 = new MasterPageItem() { Title ="Log out", Icon ="signout.png", TargetType = typeof(MainPage) };

menuList.Add(page1);
menuList.Add(page2);
menuList.Add(page3);
menuList.Add(page4);
menuList.Add(page5);

navigationDrawerList.ItemsSource = menuList;
Detail = new NavigationPage((Page)Activator.CreateInstance(typeof(Page1)));

}
private void OnMenuItemSelected(object sender, SelectedItemChangedEventArgs e)
{
var item = (MasterPageItem)e.SelectedItem;
Type page = item.TargetType;

Detail = new NavigationPage((Page)Activator.CreateInstance(page));
IsPresented = false;
}

}
}

设置类别：存储登录用户的详细信息

public static class Settings
{
public static string Token;
public static int CustId;
public static string Name;
public static string Surname;
public static string Email;
public static string MobileNo;
public static string PhoneNo;

}

App.cs-更新

public App()
{
App.Current.Properties["UserDetail"] = Settings.Token;
InitializeComponent();
var isLoggedIn = Current.Properties.ContainsKey("UserDetail");
if (!isLoggedIn)
{
MainPage = new NavigationPage(new MainPage());
}
else
{
App.Current.MainPage = (new Profile());
}

}

每次启动应用程序时，您都在加载MainPage。您必须有条件地加载第一页。

Xamarin.Forms实现Application.Current.Properties，该属性将键值数据存储在应用程序的本地存储中。

登录时：

成功登录后，将" True"值存储在应用程序的本地存储中，如IsLoggedIn所示，如下所示：

1	Application.Current.Properties ["IsLoggedIn"] = Boolean.TrueString;

在应用启动时(App.cs)

public App()
{
InitializeComponent();
bool isLoggedIn = Current.Properties.ContainsKey("IsLoggedIn") ? Convert.ToBoolean(Current.Properties["IsLoggedIn"]) : false;
if (!isLoggedIn)
{
//Load if Not Logged In
MainPage = new NavigationPage(new MainPage());
}
else
{
//Load if Logged In
MainPage = new NavigationPage(new YourPageToLoadIfUserIsLoggedIn());
}
}

登出时：

注销时，将False值存储在IsLoggedIn本地存储密钥中，然后清除导航堆栈并加载MainPage。

Application.Current.Properties ["IsLoggedIn"] = Boolean.FalseString;

存储用户详细信息：

要存储Settings类对象的值，请将其序列化为Json(Nuget包)字符串对象，并将其存储在其他某个键中，例如Application.Current.Properties中的UserDetail。
当您需要这些数据时，请从本地存储中获取数据并对其进行反序列化并使用它。

商店：App.Current.Properties["UserDetail"] = JsonConvert.SerializeObject(Settings);
检索：Settings userData = JsonConvert.DeserializeObject(App.Current.Properti??es["UserDetail"]);

编辑

Current.Properties.ContainsKey只是检查存储中是否存在某些密钥。它不检查值是否存在。在访问任何键值之前，有必要检查该键是否存在。

静态类无法序列化，因此您需要创建该类的Singleton实例，然后访问该Singleton实例进行序列化。

希望这会有所帮助！

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