How to compile Xamarin Forms from source and use the assemblies? - xamarin

Question

I downloaded a copy of the current Xamarin Forms master branch, compiled it, and then I added these compiled assemblies as references to a test project:
Xamarin.Forms.Core
Xamarin.Forms.Platform
Xamarin.Forms.Platform.Android
Xamarin.Forms.Xaml
The test project was created using the Visual Studio Xamarin Forms project template, the only thing I modified is the references in the Core.csproj and Android.csproj to point to the compiled assemblies.
I used the first 3 from the bin\debug\ folder of the Xamarin.Forms.Platform.Android project, and the last one from the Xamarin.Forms.Xaml bin\debug folder.
I run the test project, and it runs fine, I can see the label from the default generated code "Welcome to Xamarin Forms!"
Next, I just modified the MainPage like this:
public partial class App : Application
{
public App()
{
InitializeComponent();
MainPage = new NavigationPage(new ContentPage());
}
}
When I run the app, it gives me an error
System.ArgumentException: element is not of type Xamarin.Forms.View
Parameter name: element
thrown on this line:
void IVisualElementRenderer.SetElement(VisualElement element)
{
if (!(element is TElement))
throw new ArgumentException("element is not of type " + typeof(TElement), nameof(element));
SetElement((TElement)element);
}
which is strange.
The type of the element is Xamarin.Forms.NavigationPage and the stack trace is
Can someone help me running the test project with the compiled assemblies?
UPDATE #1:
The 2nd entry in the call stack shows that it's not able to get the registered renderer(NavigationPageRenderer) for the NavigationPage element and instead it's creating a default renderer(DefaultRenderer), which can't handle the type of element(NavigationPage) so it's throwing the exception I see.
So it appears that for NavigationPage, it doesn't find its renderer(NavigationPageRenderer) in the Registrar.
public static IVisualElementRenderer CreateRenderer(VisualElement element)
{
UpdateGlobalContext(element);
IVisualElementRenderer renderer = Registrar.Registered.GetHandler<IVisualElementRenderer>(element.GetType()) ?? new DefaultRenderer();
renderer.SetElement(element);
return renderer;
}
My feeling is there's a build step I'm not aware about when building Xamarin Forms.

Answer 1

Its crashing as you are calling InitializeComponent on something which doesn't derive from a Forms.Page (i.e. ContentPage etc).
The application itself is not a Page, if you had a page, lets call it 'MyCustomPage' which has some Xaml behind the class would look something like this:
public partial class MyCustomPage : ContentPage
{
public MyCustomPage()
{
InitializeComponent ();
// Some other setup...
}
}
Then in your App constructor you would call
MainPage = new MyCustomPage();
Since you are creating a blank content page from the root of your app, you do not need to call InitializeComponent.
Hope this helps.

Answer 2

You also need to reference
Xamarin.Forms.Platform.Android (Forwarders)
from your Android project.