Is there possible to use App.xaml code behind in Xamarin forms

In this project, A part of XAML is required in several places so I put it on App. Xaml it Ui part is working. but I need to add an item tapped event or anything. In order to have to go to another page, I need to use the item tapped command but in here they did not recognize its name in the app.Xaml code behind.

are there a better way to do this without put this on APP.xaml or if this is the way how to use that item tapped in here

<Application.Resources>
<ResourceDictionary>
    <ControlTemplate x:Key="PageTemplate">
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="8*"></RowDefinition>
                <RowDefinition Height="*"></RowDefinition>
            </Grid.RowDefinitions>

            <ContentPresenter Grid.Row="0"></ContentPresenter>


            <customRenderes:NavigationImageButton Source="IconFAB" Grid.Row="1"

                                                  x:Name="Button1"

                                                  AbsoluteLayout.LayoutFlags="PositionProportional"
                                                  AbsoluteLayout.LayoutBounds="1.0,1.0,-1,-1"
                                                  HorizontalOptions="EndAndExpand"
                                                  Margin="10"
                                                  Opacity="0.4"
                                                  ItemTapped="Button1_OnItemTapped"/>
     </Grid>

    </ControlTemplate>
     </ResourceDictionary>
     </Application.Resources>

I need to do some function when this floating menu is tapped how to do this are a there better way to do this without doing it on App.Xaml or If this is the way How to do this