Xamarin.forms iOS WkWebView 在后台运行

Question

我有带有 EmbedIO 网络服务器的应用程序和 angular WebView 中带有 WkWebViewRenderer 的代码。 Angular 中的代码是轮询函数。

当应用程序进入后台时 DidEnterBackground 被调用并且我处理了网络服务器，但网络视图仍在运行。如何在触发此事件时使用 Angular 暂停 webview 以停止轮询，并在应用程序再次进入前台时再次启动它？

Answer 1

所以，我想出了一些解决方案来满足某些人的兴趣，我在我的应用程序中使用 AppShell 进行导航..

这是我的 EmbedIO 网络服务器助手 class:

public  class WebServerHelper
{
    private static readonly Lazy<WebServerHelper> lazy = new(() => new WebServerHelper());

    public static WebServerHelper Instance => lazy.Value;

    private CancellationTokenSource _cts;
    private WebServer _webServer = null;

    public void Run()
    {
        if(_webServer == null)
        Task.Factory.StartNew(async () =>
        {
            using (_cts = new CancellationTokenSource())
            using (_webServer = CreateWebServer())
            {
                await _webServer.RunAsync(_cts.Token);
            }                
        });
    }

    public void Stop()
    {
        _cts.Cancel();
        _cts = null;
        _webServer = null;
    }

    private WebServer CreateWebServer()
    {
        var server =  new WebServer(o => o
            .WithUrlPrefix($"http://localhost:8080")
            .WithMode(HttpListenerMode.EmbedIO))
        .WithCors()
        .WithLocalSessionManager()
        .WithWebApi("/api", m => m
            .WithController<TestController>()
            ...
            .WithController<SystemController>())
        .WithModule(new ActionModule("/", HttpVerbs.Any,
            ctx => ctx.SendDataAsync(new { Message = "Error" })));

        Trace.TraceInformation($"WebApi started on port: 8080");

        server.OnUnhandledException += (s, e) => { Trace.TraceInformation("Unhadled Exception occured"); return Task.CompletedTask; };
        server.OnHttpException += (s, e) => { Trace.TraceInformation("Http exception occured"); return Task.CompletedTask; };

        return server;
    }
}

然后我按照描述创建了混合网络视图here

这一切都在 AppDelegate 中运行，例如：

    public override bool FinishedLaunching(UIApplication app, NSDictionary options)
    {
        Forms.Init();

        WebServerHelper.Instance.Run();

        ...

        LoadApplication(new App());

        return base.FinishedLaunching(app, options);
    }

    public override void WillTerminate(UIApplication application)
    {
        application.Dispose();
        base.WillTerminate(application);
    }

    [Export("applicationWillEnterForeground:")]
    public override void WillEnterForeground(UIApplication application)
    {
        //TODO: handle situation when user goes foreground (eg. double tap on start button and turn camera on)
        WebServerHelper.Instance.Run();

        ((WKWebView)((HybridWebView)((WebContainer)((IShellSectionController)Shell.Current?.CurrentItem?.CurrentItem)?.PresentedPage).Content).GetRenderer().NativeView).GoForward();
    }

    [Export("applicationDidEnterBackground:")]
    public override void DidEnterBackground (UIApplication application)
    {
        ((WKWebView)((HybridWebView)((WebContainer)((IShellSectionController)Shell.Current?.CurrentItem?.CurrentItem)?.PresentedPage).Content).GetRenderer().NativeView).GoBack();

        //In background task cancelation token is called dispose of webserver.
        //This step obtain aditional (aprox.) 25 seconds to finish all ongoing operations.
        application.BeginBackgroundTask(() => {
            WebServerHelper.Instance.Stop();
        });
    }

Xamarin.forms iOS WkWebView 在后台运行

Xamarin.forms iOS WkWebView runs in background

xamarin.ios

xamarin.forms