从JavaScript中的回调函数获取结果

Question

I'm writing a Javascript function which will be called by a C# application. I can call the function from C#, but have been unable to retrieve the result of the function.

So I have the following structure:

var B = function() {
    var A = function() {
        var dfd = new $.Deferred();
            // do something and then return the value I need
            return dfd.resolve(x);
        ......
        return dfd.promise();
    }
    $.when(A()).
        then(function(x) {
            // I can get the x I want here.
            alert(x);
            // What to do at this point?
        });
}

Since A() used asynchronous methods, I chose to use jQuery.promise() method to ensure I get the final result of A() . Now I want B() to return the value x to the C# application. Is there any good solution to this?

Answer 1

I assume that you've called your Javascript function by calling WebView method InvokeScriptAsync with Js function name as a parameter.

The problem here is that your JavaScript function is an asynchronous since it uses promise - so you cannot simply get its return value on C#. The IAsyncOperation ends as the promise object has been returned, not as it has been resolved.

If your javascript function was synchronious:

The return value of the InvokeScriptAsync function is the string result of the script invocation - so if you'll wait for it you'll get the result.

MSDN documentation : https://msdn.microsoft.com/en-us/library/windows.ui.xaml.controls.webview.invokescriptasync.aspx?f=255&MSPPError=-2147217396

However, you can always invoke webView event by calling windows.external.invoke with string parameter from JavaScript and get it on C# by subscribing to webView ScriptNotify event.