[Bug] Shell query parameter not being set before OnAppearing of page is called

[tsequeira-vhs]

Description

Shell page parameter navigation does not set parameter for page before OnAppearing is called. In prior releases, the OnAppearing used to be called after the paramters were set allowing us to load the content based on the parameter.

Steps to Reproduce

1. Use Shell page and add 2 pages
2. Navigate from page 1 to page 2 using GoToAsync("Page2?id=5");
3. Observe that OnAppearing of page 2 is called before the id parameter is set

Expected Behavior

The parameter set should be called before the OnAppearing is called

Actual Behavior

OnAppearing of page 2 is called before the id parameter is set

Basic Information

• Version with issue: Xamarin.Forms 4.7.0.1080
• Last known good version: Xamarin.Forms 4.6.x and versions below

[tsequeira-vhs]

Will this issue be fixed in 5.0.0?

[elcainas]

I tested in Xamarin.Forms 4.6.x , 4.8.x same issue

[tsequeira-vhs]

@samhouts Does this mean that this issue will no longer be fixed?

[attilavlacsil]

With 4.8.0.1687 I have the same issue, but the actual behavior happens only if I navigate to the page for the first time, any subsequent navigation works as expected.

If I have a similar page to track constructor, query property and OnAppearing call order

[QueryProperty(nameof(QueryData), nameof(QueryData))]
public partial class ShellPage : ContentPage
{
    private readonly ShellPageViewModel viewModel;

    public string QueryData
    {
        set
        {
            Trace.WriteLine("ShellPage.QueryData setter");

            viewModel.QueryData = value;
        }
    }

    public ShellPage()
    {
        Trace.WriteLine("ShellPage ctor");

        InitializeComponent();
        BindingContext = viewModel = new ShellPageViewModel();
    }

    protected override void OnAppearing()
    {
        Trace.WriteLine("ShellPage.OnAppearing");

        base.OnAppearing();
    }
}

Navigating to the page for the first time outputs

[0:] ShellPage ctor
[0:] ShellPage.OnAppearing
[0:] ShellPage.QueryData setter

Any subsequent navigation outputs

[0:] ShellPage.QueryData setter
[0:] ShellPage.OnAppearing

As mentioned, the order must be consistent for any given navigation.

[archergod]

I am having same Issue with 5.0.0.2012

[andrybany]

I have also had this problem for some time.
A little while ago I just discovered that it can be remedied like this:

protected async override void OnAppearing()
{
    base.OnAppearing();
    await Task.Yield();
    //DO some stuff with QueryProperty populated 
}