CODEWITHSUNDEEP
androidxamarin
vaid
vaid

Reputation: 1540

Back button restores unwanted previous page in Android on Xamarin

I am developing an app that starts with a login page, called LoginPage.

Once logged in a different page is viewed, called UserPage.

Once LoginPage has been popped and UserPage has been pushed, I press the back button on the Android device, which takes me to the home screen.

Once at the home screen I reopen the app from the app manager (the little square button at the lower right side of the device) and the LoginPage reappears.

Why is that?

My code to pop the LoginScreen is as following:

Application.Current.MainPage = new UserPage();
await Navigation.PopToRootAsync(true);

EDIT 1 Main app method

    public App()
    {
        InitializeComponent();

        var navPage = new NavigationPage(new LoginPage());
        NavigationPage.SetHasNavigationBar(navPage.CurrentPage, false);

        MainPage = navPage;
    }

Upvotes: 2

Views: 1441

Answers (3)

Mike Ma
Mike Ma

Reputation: 2027

Once at the home screen I reopen the app from the app manager (the little square button at the lower right side of the device) and the LoginPage reappears.

According your code : 

Application.Current.MainPage = new UserPage();
await Navigation.PopToRootAsync(true);

Pop up the login page and set the main page is UserPage. At this time your page stack only have the UserPage. When you click the back button. The app has been killed by the system.

But android will keep app the shot cut at the app manager. When you click the shot cut in fact you are reopening your app. And your MainPage is LoginPage so you will see your LoginPage again.

I have added the output message in the app init function:

App Init:

public App()
{
    InitializeComponent();
    System.Diagnostics.Debug.WriteLine("ini app again");
    MainPage = new NavigationPage(new MainPage());
}

MainPage Init

public MainPage()
{
    System.Diagnostics.Debug.WriteLine("init Mainpage again");
    InitializeComponent();
}

When I click the button pop up the mainpage and go to page1: 

private async void bt1_Clicked(object sender, EventArgs e)
{
      Application.Current.MainPage = new Page1();
      await Navigation.PopToRootAsync(true);
}

Run you my code you will find when you click the back button you actually open the app again and it will show the mainpage again:

enter image description here

Upvotes: 2

Alessandro Caliaro
Alessandro Caliaro

Reputation: 5768

I think you should take a look if your app enter in 

    protected override void OnResume()

or

    protected override void OnStart()

Can be that when you put your app in background, your app has been killed by OS so, when you reopen it, it start from the "Start", so from the "Login".

I think you can save a boolean flag in your

Application.Current.Properties

When your app starts, if this flag is true you start from UserPage, otherwise you Start from LoginPage

Upvotes: 0

blas3nik
blas3nik

Reputation: 1381

Your application's main page does not have a navigation stack where it could store the pushed/popped pages.

Can you just try and change your code to be:

Application.Current.MainPage = new NavigationPage(new UserPage());

This should create a NavigationPage wrapper around your userpage that will have the pre-built stack to use for popping and pushing to.

Upvotes: 0

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