How to send events from HTML running inside a UIWebView to native Objective-C code?

I want to integrate a full HTML framework (ie HTML/CSS/JavaScript) inside an iOS app and make the UIWebView in charge of running the HTML content being able to communicate with the rest of the native Objective-C source code.

Direction 1: from Objective-C to HTML inside a UIWebView

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  • The way to make the rest of the source send messages to the HTML content is pretty straightforward: i can just call stringByEvaluatingJavaScriptFromString: on the Objective-C side and implement JavaScript methods the right way.

    Direction 2: from HTML inside a UIWebView to Objective-C

    This is the way I can’t really figure out. My only idea so far is to make my app a local web server and make the HTML request stuff to it. But I have no idea how to do that although I suppose it can be bone as I believe apps such as Things, VLC or 1Password might use this kind of features.

    Any idea to make this direction 2 work or any new perspective to make events inside HTML content being sent to Objective-C code is welcome.

    4 Solutions Collect From Internet About “How to send events from HTML running inside a UIWebView to native Objective-C code?”

    I have done this using jQuery and UIWebViewDelegate:

    JavaScript (jQuery mobile):

    $("#bloodType").change(function() {
        url = $("#bloodType option:selected").text();
        url = "donordialog:bloodTypeChanged(" + url + ")";
        window.location = url;
    });
    

    So, the resulting URL looks like: donordialog:bloodTypeChanged(typeAB-)

    In my objc code:

    -(BOOL) webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
    {
        NSURL *URL = [request URL];
        if ([[URL scheme] isEqualToString:@"donordialog"])
        {
            // now we need to figure out the function part
            NSString *functionString = [URL resourceSpecifier];
    
            if ([functionString hasPrefix:@"bloodTypeChanged"])
            {
                // the blood type has changed, now do something about it.
                NSString *parameter = [functionString stringByReplacingOccurrencesOfString:@"bloodTypeChanged" withString:@""];
    
                // remove the '(' and then the ')'
                parameter = [parameter stringByReplacingOccurrencesOfString:@"(" withString:@""];
                parameter = [parameter stringByReplacingOccurrencesOfString:@")" withString:@""];
    
                // log the paramter, as I don't know what to do with it right now
                NSLog(@"%@", parameter);
            }
    
            return NO;
        }
    
        return YES;
    }
    

    This code was copied verbatim from a project I am currently working on, and can verify that this works.

    I just created a library that will do this for you. It supports two-way communication between your web app and iOS about through JSON, relying heavily on this method. Check it out: https://github.com/tcoulter/jockeyjs

    The way you usually talk back from JavaScript is by opening a fictional URL (by window.location), and then implementing UIWebViewDelegate‘s -webView:shouldStartLoadWithRequest:navigationType: to ignore the navigation and handle what needs to be done instead.

    (On Mac OS X WebKit, you can supply Objective-C objects that have JavaScript functions to the web site, but this is not available in iOS.)

    PhoneGap was built exactly for this