The OnAppearing event fires twice. With tab

Question

I ran into a problem that is new to Xamarin and MVVM forms. I have a tab and 2 pages are under the tag. Here is the code.   
        
             

The problem is local: the ActiveOrderViewPage page. The OnAppearing () event is fired twice when the tabbedPage is loaded and the code is executed twice in the OnAppearing () event.

Please help me find this, why is this happening?

Here is the code with tabbedpage.xaml tab

<TabbedPage
        xmlns="http://xamarin.com/schemas/2014/forms"
        xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
        Title="Orders">
<TabbedPage.Children>  
      <local:ActiveOrderViewPage />  
      <local:SavedOrderViewPage />
</TabbedPage.Children>

tabbedpage.xaml.cs

  public partial class OrderTabViewPage : TabbedPage
{
    public OrderViewModel ViewModel { get { return BindingContext as OrderViewModel; } }
    public OrderTabViewPage()
    {
        InitializeComponent();
     this.BindingContext = ViewModelLocator.OrderVModel;

    }
    public OrderTabViewPage(params object[] arg) : this()
    {
        if (arg != null)
        {
            ViewModel.AccountID = Convert.ToInt32(arg[0]);
        }
    }

Here is the active .cs order

 public partial class ActiveOrderViewPage : ContentPage
{
    public OrderViewModel ViewModel { get { return BindingContext as OrderViewModel; } }
    public ActiveOrderViewPage()
    {
        InitializeComponent();
      this.BindingContext = ViewModelLocator.OrderVModel;       
    }

    //public OrderViewPage() : this()
    //{
    //    ViewModel.AccountID = accuntId;
    //}
    protected override void OnAppearing()
    {
        base.OnAppearing();
        if (ViewModelLocator.OrderVModel.ActiveOrderItems == null || ViewModelLocator.OrderVModel.ActiveOrderItems.List.Count == 0)
        {
            ViewModelLocator.OrderVModel.ActiveOrderCommand.Execute(null);
        }


    }

Thanks in advance...

Answer 1

, , , . OnAppearing() - , . , , OnDisappearing(). , OnAppearing() .

, , , currentpage null, OnAppearing()