How can I detect the clicking of a tab button in Xamarin.Forms?

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.

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);
    }
}

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?