URI start of MAUI Windows app creates a new instance. I need to have only one instance of app

Question

I am able to start my Windows MAUI app using an URI, and I can get the URI itself. But, it appears that a NEW instance of the app is being created. This is not ideal for me -- if my app is already running, I want to use that instance.

I have done something like this for a Xamarin.Forms app. I override OnActivated in Application class.

Re: my MAUI app, I'm not even clear on whether the issue is how I've done the "protocol" in package.appxmanifest, or if it is how I respond to lifecycle events.

Answer 1

The default behaviour is to run multiple instances of your app. You can make the app single-instanced by defining a customized class with a Main method as suggested in this blog post:

[STAThread]
static async Task Main(string[] args)
{
    WinRT.ComWrappersSupport.InitializeComWrappers();
    bool isRedirect = await DecideRedirection();
    if (!isRedirect)
    {
        Microsoft.UI.Xaml.Application.Start((p) =>
        {
            var context = new DispatcherQueueSynchronizationContext(
                DispatcherQueue.GetForCurrentThread());
            SynchronizationContext.SetSynchronizationContext(context);
            new App();
        });
    }
    return 0;
}

private static async Task DecideRedirection()
{
    bool isRedirect = false;
    AppActivationArguments args = AppInstance.GetCurrent().GetActivatedEventArgs();
    ExtendedActivationKind kind = args.Kind;
    AppInstance keyInstance = AppInstance.FindOrRegisterForKey("randomKey");

    if (keyInstance.IsCurrent)
    {
        keyInstance.Activated += OnActivated;
    }
    else
    {
        isRedirect = true;
        await keyInstance.RedirectActivationToAsync(args);
    }
    return isRedirect;
}

There is an open suggestion to simplify this process available on GitHub.