Howto get more information about break state

Question

hi
I am new to Xamarin programming.
I am trying to make an app that displays a SurfaceView for video capture.
I have referenced the nuget package Xam.WebRtc.Android that uses a renderer called SurfaceViewRenderer that displays the SurfaceView.
I would like to create a custom renderer that inherits from the SurfaceViewRenderer hoping to be able to use in from the shared xamarin project.
This is how i implement my renderer:

[assembly: ExportRenderer(typeof(CameraView), typeof(CameraPreviewRenderer))]
namespace mobile.friends.Droid.CameraRenderer
{
    public class CameraPreviewRenderer : SurfaceViewRenderer
    {
        public CameraPreviewRenderer(Context context) : base(context)
        {
            this.SetBackgroundColor(Android.Graphics.Color.Red);
        }
    }
}

and this is how i have implemented my shared view:

public class CameraView : View
    {
        public CameraView()
        {

        }
    }

i then add it in the xaml like this:

<?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                 xmlns:local="clr-namespace:mobile.friends.Camera"
                 x:Class="mobile.friends.MainPage">


        <local:CameraView HeightRequest="100" WidthRequest="100"/>
    </ContentPage>

during debug i can see that my custom renderer is called in it's constructor.
my problem is that the app throws an exception and the only information i get about it is:

Your app has entered a break state, but there is no code to show because all threads were executing external code (typically system or framework code).
System.InvalidCastException: 'Specified cast is not valid.'

I have tried to enable all exceptions in Visual Studio Exception settings.

How do i get more information about what goes wrong?
is there a way to get more information

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

You create a custom renderer for Xamarin.Forms.View, but the Xamarin.Forms.View's renderer base class is IViewRenderer, not the SurfaceViewRenderer, when you create custom renderer, so you will get the System.InvalidCastException: 'Specified cast is not valid.'

To create a cameraView with custom renderer view, You can refer to following thread:

https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/view

Here is source code.

https://github.com/xamarin/xamarin-forms-samples/blob/master/CustomRenderers/View/Droid/CameraPreviewRenderer.cs

If you want to create a custom renderer for xamarin forms controls, you should refer this thread to get the renderer base class and Native Controls, then create a custom renderer for your control.

:https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/renderers

Best Regards,

Leon Lu

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