Event of button is not getting fired in absolute layout

Hello All,
I am facing an strange behavior in Xamarin.forms.

When i m writting below xaml code it's working fine as expected but the same thing i m trying to achieve dynamically from code behind event for button is not getting fired.
XAML code:

<AbsoluteLayout>
    <Button x:Name="firstChild" Text="First Child"></Button>
    <AbsoluteLayout Padding="70">
        <Label Text="inner child"></Label>
    </AbsoluteLayout>
    </AbsoluteLayout>

Below is my .cs code which is trying to achieve the same thing but event is not getting fired.

public partial class TestPage : ContentPage
{

    MR.Gestures.AbsoluteLayout mainLayout = new MR.Gestures.AbsoluteLayout ();
    Button firstChild = new Button {
        Text = "First Child",
        TextColor = Color.White,
        BackgroundColor = Color.Red 
    };

    MR.Gestures.AbsoluteLayout innerLayout = new MR.Gestures.AbsoluteLayout {Padding=70};
    Label innerLabel=new Label{
        Text="inner child",
        TextColor=Color.Red
    };

    public TestPage ()
    {
        InitializeComponent ();
        firstChild.Clicked += btnclick;
        mainLayout.Children.Add (firstChild);
        innerLayout .Children.Add (innerLabel);
        mainLayout.Children.Add (innerLayout );


        this.Content = mainLayout;
    }
    void btnclick(object sender,EventArgs args)
    {
        DisplayAlert ("Hello", "Hello World", "OK");
    }
}