title: How can I detect the clicking of a tab button in Xamarin.Forms?
body: <p>Here is the code that I have.  I would like to know how I can detect when a user clicks a tab that is already selected as I want to toggle the icon for the aPage between play.png and pause.png plus I also want to call a method on APage.</p>
  
  <pre class="lang-cs prettyprint-override"><code>public partial class MainPage : TabbedPage
  {
      public MainPage()
      {
          InitializeComponent();
  
          var aPage = new NavigationPage(new APage())
          {
              Title = "Play",
              Icon = "play.png"
          };
          var bPage = new NavigationPage(new BPage())
          { 
              Title = "Settings",
              Icon = "b.png"
          };
  
          Children.Add(aPage);
          Children.Add(bPage);
      }
  }
  </code></pre>
  
  <p>Note that if possible I would like to find a solution that does not involve custom renderers for both iOS and Android.  I'm wondering can I redefine the TabbedPage and put the logic in that class?</p>