有一个API可直接从Objective-C调用Javascript， 但不能直接从Javascript调用Objective-C。
如何告诉您的Objective-C代码通过WebView中的Java脚本执行某些操作
您必须将Javascript操作序列化为一个特殊的URL，并在UIWebView的委托
shouldStartLoadWithRequest方法中截取该URL
。
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType;
在这里，您可以反序列化该特殊URL并对其进行解释，以实现Objective-
C方面的目标。（您应该返回
NO上述
shouldStartLoadWithRequest方法，以便UIWebView不会使用您的虚假URL实际发出HTTP请求来加载网页。）
如何从Objective-C运行Javascript代码
然后，您可以通过在Webview上调用此方法来从Objective-C运行Javascript。
- (NSString *)stringByevaluatingJavascriptFromString:(NSString *)script;
范例程式码
我建议使用伪造的URL方案，这样很容易分辨出操作URL和合法请求之间的区别。您可以按照以下方式在Javascript中发出此请求：
// Javascript to send an action to your Objective-C prevar myAppName = 'myfakeappname';var myActionType = 'myJavascriptActionType';var myActionParameters = {}; // put extra info into a dict if you need it// (separating the actionType from parameters makes it easier to parse in ObjC.)var jsonString = (JSON.stringify(myActionParameters));var escapedJsonParameters = escape(jsonString);var url = myAppName + '://' + myActionType + "#" + escapedJsonParameters;document.location.href = url;然后，在
UIWebView.delegate的
shouldStartLoadWithRequest方法中，您可以检查URL方案和片段，以检查这是正常请求还是您的特殊操作之一。（URL的片段位于后面
#。）
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType { // these need to match the values defined in your Javascript NSString *myAppScheme = @"myfakeappname"; NSString *myActionType = @"myJavascriptActionType"; // ignore legit webview requests so they load normally if (![request.URL.scheme isEqualToString:myAppScheme]) { return YES; } // get the action from the path NSString *actionType = request.URL.host; // deserialize the request JSON NSString *jsonDictString = [request.URL.fragment stringByReplacingPercentEscapesUsingEncoding:NSASCIIStringEncoding]; // look at the actionType and do whatever you want here if ([actionType isEqualToString:myActionType]) { // do something in response to your javascript action // if you used an action parameters dict, deserialize and inspect it here } // make sure to return NO so that your webview doesn't try to load your made-up URL return NO;}
