Xamarin.Forms: Display additional tab on specific Platform - xamarin.forms

Question

Good morning
I have a TabbedPage in my application. Due to restictions I would like to display one more tab on Android than on iOS.
My current TabbedPage look like:
<TabbedPage>
...
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<ContentPage x:Name="Page3"/>
<ContentPage x:Name="Page4"/>
</TabbedPage>
I have decided to render Page3 only for Android. I changed my code into:
<TabbedPage>
...
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<OnPlatform x:TypeArguments="Page">
<On Platform="Android">
<On.Value>
<ContentPage x:Name="Page3"/>
</On.Value>
</On>
</OnPlatform>
<ContentPage x:Name="Page4"/>
</TabbedPage>
This leads to runtime exception when entering into this TabbedPage:
An error occurred: 'Value cannot be null. Parameter name: item'.
Callstack: ' at
Xamarin.Forms.ObservableWrapper`2[TTrack,TRestrict].Add (TRestrict
item) [0x00008] in D:\a\1\s\Xamarin.Forms.Core\ObservableWrapper.cs:27
I tried to remove x:Name but did not work. Any ideas?
PS. As a workaround I am always able to:
Constructor()
{
if(Runtime.IsIOS)
{
this.Children.Remove(this.Page3)
}
}
However would be better to not render it at all and have it at XAML level.

Answer 1

Unless someone comes up with a way to do this in XAML, this is the best you can do (building on Jason's comment):
xaml:
<ContentPage x:Name="Page1"/>
<ContentPage x:Name="Page2"/>
<!-- no Page3 in XAML -->
<ContentPage x:Name="Page4"/>
c#:
private ContentPage page3;
Constructor()
{
InitializeComponent();
if (Runtime.IsAndroid)
{
page3 = new ContentPage();
// After pages 1 and 2.
Children.Insert(2, page3);
}
}
// Elsewhere in code-behind.
if (page3 != null)
{
...refer to page3...
}
This has the advantage of not constructing the page at all on iOS.
It also makes it easy to test whether page3 is there (page3 != null).
In practice, the other pages will typically be their own classes. Given partial class Page3 : ContentPage elsewhere:
private Page3 page3;
...
page3 = new Page3();

Answer 2

According to this,xaml is an alternative to programming code for instantiating and initializing objects, and organizing those objects in parent-child hierarchies.If you add one additional tab on android it will cause a NullReferenceException on ios.So you may want to do it in codebehind with Device.RuntimePlatform.
Here is my test you can refer to:
switch (Device.RuntimePlatform)
{
case Device.Android:
Children.Add(page1);
Children.Add(page2);
break;
case Device.iOS:
Children.Add(page1);
break;
case Device.UWP:
Children.Add(page1);
break;
}