Xamarin Forms: How do you Navigate to a New View Immediately After the Previous View Loads Using ViewModels

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NicholasR-0309 asked · Mar 16 at 09:31 PM

Xamarin Forms: How do you Navigate to a New View Immediately After the Previous View Loads Using ViewModels

In my app, users have to login the first time, but a token is generated to allow them to skip the login process on subsequent logins. The login page checks that the token is correct in its viewmodel constructor, calling Shell.Current.GoToAsync() if it is. This does not work as it should, as the login page was not completely loaded when the new page was pushed, and will load on top of the new page. I have tried the workaround in this question, but that does not work either. Here's a part of the code:

         public LoginPageViewModel()
         {
             userData = (Application.Current as App).userData;
             SendLogin = new Command(Login);
             TokenLogin();
         }
    
         //Attempts to login via token
         private async void TokenLogin()
         {
             string user = Tokenizer.GetTokenUser();
             string token = Tokenizer.GetToken();
             if(userData.TokenLogin(user, token))
             {
                 await Shell.Current.GoToAsync(nameof(CategoryPage));//Login successful
             }
         }

dotnet-xamarinforms

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Answer 1 · 2021-03-16T23:48:53.497Z

sphauck answered · Mar 16 at 11:48 PM

Look for the token on startup and then don't even go to the login window, go directly to the "second form"
FYI, if you are storing a "token" make sure you are using secure storage
https://docs.microsoft.com/en-us/xamarin/essentials/secure-storage?context=xamarin%2Fandroid&tabs=ios

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Answer 2 · 2021-03-17T07:30:18.637Z

ColeXia-MSFT answered · Mar 17 at 07:30 AM

Hello,

Welcome to Microsoft Q&A!

The better way is that set LoginPage as MainPage at first ,and then change App.Current.MainPage upon login successfully .

App

MainPage =  new LoginPage();

LoginPageViewModel

private async void TokenLogin()
         {
             string user = Tokenizer.GetTokenUser();
             string token = Tokenizer.GetToken();
             if(userData.TokenLogin(user, token))
             {
                 App.Current.MainPage = new AppShell();
             }
         }

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