Best practice: How to call Objective-C code from JavaScript

Question

I've been looking for a way to call Objective-C code from some JavaScript in my UIWebView . A lot of topics has been created about this, and some of them are recommending the procedure done in the blog post UIWebView Secrets - Part3 - How to Properly Call ObjectiveC From Javascript , where UIWebViewDelegate methods are hacked to call native Objective-C code from. Is this still the best way to do this? It seems that PhoneGap has a way to do this, but I cannot find out how to. But if their procedure is equal to this, I cannot see why I should include their library just to do this.

Which procedure is currently best practice to do this?

Answer 1

Without any external framework we can do that.To achieve this like phone we have to use webView. For example, If you need to call an objective c function when a button is clicked in the webview.When the onclick of your button in the html page calls a javascript, just add an iFrame which will include the function name of the objective C function.

eg:

var iframe = document.createElement("IFRAME");
    iframe.setAttribute("src", "js-frame:" + functionName + ":" + callbackId);
    document.documentElement.appendChild(iframe);
    iframe.parentNode.removeChild(iframe);
    iframe = null

;

This iFrame can be accesed in your webView Delegate implemented in your ParentView of the webView, like-

- (BOOL)webView:(UIWebView *)webView2 
shouldStartLoadWithRequest:(NSURLRequest *)request 
 navigationType:(UIWebViewNavigationType)navigationType {

    NSString *requestString = [[request URL] absoluteString];




    if ([requestString hasPrefix:@"js-frame:"]) {

        NSArray *components = [requestString componentsSeparatedByString:@":"];

        NSString *function = (NSString*)[components objectAtIndex:1];
        int callbackId = [((NSString*)[components objectAtIndex:2]) intValue];

                                  stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        ;

        [self handleCall:function callbackId:callbackId];

        return NO;
    }

    return YES;
}

The handleCall will have to handle the invoking of your intended method having name "function"

Answer 2

There is no (public) API to do this other than using a custom URL scheme inside your JS code to invoke javascript.

Let's say you load the URL myproto://invokeMethodA in your JS code like so

window.location.href = "myproto://invokeMethodA";

you can intercept that load in UIWebView s delegate method

– webView:shouldStartLoadWithRequest:navigationType:

and do your stuff. Make sure you return NO to not actually perform the the request.

Answer 3

我最终使用了博客文章中推荐的NativeBridge插件。