title: Tabbed Page OnAppearing()
body: <p>I have a Tabbed Page Xamarin Form application that I am trying to customize. I am migrating from an IOs only app to all platforms. In iOS there are a couple function that I used ViewDidDisappear(), ViewDidAppear() and ViewDidLoad();</p>
  
  <p>The application today loads the tabbed page as follows:</p>
  
  <pre><code>{
      Children.Add(new MyPage1());
      Children.Add(new MyPage2());
      Children.Add(new MyPage3());
      Children.Add(new MyPage4());
  }
  </code></pre>
  
  <p>Each of the child pages are declared as follows all inheriting from ContentPage.</p>
  
  <pre><code>class MyPage1: ContentPage
  {
          …
          protected override void OnAppearing()
          {
              base.OnAppearing();
              Content = SomeContentPage;
          }
  }
  </code></pre>
  
  <p>The problem that I am running into is that the OnAppearing() is called for all pages when only MyPage1 is currently displayed. I need to know when each child page is loaded.</p>
  
  <p>I have read about message center but I am not sure how to implement it in this particular case. Would the message center be the best solution for this?</p>
  
  <p>How do I implement a solution that will allow me to know which of the four pages is displayed?</p>