System.InvalidOperationException: 'Cannot assign a native control without an Element;

Question

I am working on a project "CoManga" and I wanted to add advertisements in it. Implementing ads on UWP seemed straight forward, like Android and iOS. However, I'm stuck now.

Anyways, I followed this tutorial by James Montemagno and added everything. I even see the test advertisements, which is great. However, when I try to move away from that page (when I press "BACK Button") and go to previous page, I get an error.

This is the error :

Setting up AdControlView in UWP throws System.InvalidOperationException: 'Cannot assign a native control without an Element; Renderer unbound and/or disposed. Please consult Xamarin.Forms renderers for reference implementation of OnElementChanged.'.

It is thrown at line number 50, where I set the SetNativeControl(adView);. I've commented it out right now, but as soon as I un-comment it, I see this error.

Can someone help me out here with this.

Answer 1

Setting up AdControlView in UWP throws System.InvalidOperationException: 'Cannot assign a native control without an Element; Renderer unbound and/or disposed. Please consult Xamarin.Forms renderers for reference implementation of OnElementChanged.

The reason is that xamarin Element has released but SetNativeControl invoked again cause the native control can't find the matched xamarin Element when page going back. So you could set a flag (isRegist) to record the registed ad.

public class AdViewRenderer : ViewRenderer<AdControlView, AdControl>
{
    string bannerId = "test";
    AdControl adView;
    string applicationID = "3f83fe91-d6be-434d-a0ae-7351c5a997f1";
    bool isRegist = false;

    protected override void OnElementChanged(ElementChangedEventArgs<AdControlView> e)
    {
        base.OnElementChanged(e);

        if (Control == null && isRegist != true)
        {
            CreateNativeAdControl();
            SetNativeControl(adView);
            isRegist = true;
        }
    }
    private void CreateNativeAdControl()
    {
        if (adView != null)
            return;

        var width = 300;
        var height = 50;
        if (AnalyticsInfo.VersionInfo.DeviceFamily == "Windows.Desktop")
        {
            width = 728;
            height = 90;
        }
        // Setup your BannerView, review AdSizeCons class for more Ad sizes. 
        adView = new AdControl
        {
            ApplicationId = applicationID,
            AdUnitId = bannerId,
            HorizontalAlignment = Windows.UI.Xaml.HorizontalAlignment.Center,
            VerticalAlignment = Windows.UI.Xaml.VerticalAlignment.Bottom,
            Height = height,
            Width = width
        };
    }
}