WKWebView.EvaluateJavaScript 从不返回

问题描述：

我正在尝试使用 WKWebView.EvaluateJavaScript(string, WKJavascriptEvaluationResult) 从我的 javascript 代码获取一个值返回到我的应用程序.问题是，委托 WKJavascriptEvaluationResult 从未被调用.这是我的代码:

I'm trying to get a value from my javascript code back to my application using WKWebView.EvaluateJavaScript(string, WKJavascriptEvaluationResult). The problem is, the delegate WKJavascriptEvaluationResult is never called. Here's my code:

C#:

TaskCompletionSource<NSObject> tcs = new TaskCompletionSource<NSObject>();

webView.EvaluateJavaScript(javascript, (result, error) =>
    {
        tcs.SetResult(result);
    });

return tcs.Task.Result;

Javascript:

function a()
{
    return "test";
}

a();

应用程序停留在 Wait() 调用上并且永远不会返回，因为 WKJavascriptEvaluationResult 永远不会被调用.是否有我不知道的已知问题?有没有更好的方法可以将我的 javascript 代码中的值获取到我的应用程序中，还是我没有正确使用它?

The application is stuck on the Wait() call and never returns because the WKJavascriptEvaluationResult never gets called. Is there a know issue that I'm not aware of? Is there a better way to get values from my javascript code to my application, or am I not using it correctly?

注意:我使用 TaskCompletionSource 只是为了使整个方法同步.

Note: I'm using a TaskCompletionSource simply to make the whole method synchronous.

答

如果您使用 Xamarin IOS，在 Xamarin Forms 中为我工作应该是相同的.

Worked for me in Xamarin Forms should be the same if you are using Xamarin IOS.

    public class IosWebViewRenderer : ViewRenderer<HybridWebView, WKWebView>
    {
        const string HtmlCode = "document.body.outerHTML";

        protected override void OnElementChanged(ElementChangedEventArgs<HybridWebView> e)
        {
            base.OnElementChanged(e);
            if (Control == null)
            {
                WKWebView wKWebView = new WKWebView(Frame, new WKWebViewConfiguration());
                wKWebView.NavigationDelegate = new WebViewDelate();
                SetNativeControl(wKWebView);
            }
            if (e.NewElement != null)
            {
                NSUrlRequest nSUrlRequest = new NSUrlRequest(new NSUrl(hybridWebView.Uri.ToString()));
                Control.LoadRequest(nSUrlRequest);
            }
        }

        class WebViewDelate : WKNavigationDelegate
        {
            public override void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
            {
                WKJavascriptEvaluationResult handler = (NSObject result, NSError error) => {
                    if (error != null)
                    {
                        Console.WriteLine(result.ToString());
                    }
                };
                webView.EvaluateJavaScript(HtmlCode, handler);
            }
        }
    }

WKWebView.EvaluateJavaScript 从不返回

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