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JavaScript and OC Interaction in iOS

Source: Internet
Author: User
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In the development of iOS many times we will deal with UIWebView, many domestic applications are now using UIWebView hybrid programming technology, the most common is the public number of content pages. Some time ago in the public platform related development, found that many applications are using HTML5 and UIWebView to achieve.

Mechanism

Objective-c language calls JavaScript language, is through the UIWebView - (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script; method to achieve. This method passes a piece of JavaScript code that needs to be executed to UIWebView and finally gets the execution result.

The JavaScript language calls the Objective-c language, and there is no ready-made API, but there are some ways to achieve that. Specifically, the UIWebView feature is used: all network requests initiated within the UIWebView can be notified via the delegate function.

Example

Here is a simple example of how to call each other, the effect is to click on a link on the interface, and then pop up a dialog box to determine whether the login is successful.

(1) The source code for the example HTML is as follows:

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            <meta http-equiv="content-type" content="text/html;charset=utf-8" />        <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <meta content="always" name="referrer" /> <title>测试网页</title>  <body> <br /> <a href="devzeng://login?name=zengjing&password=123456">点击链接</a> </body>

(2) UIWebView delegate callback method is:

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-(BOOL) WebView: (UIWebView *) WebView shouldstartloadwithrequest: (nsurlrequest *) Request Navigationtype: ( Uiwebviewnavigationtype) Navigationtype{Nsurl *url = [request URL];if ([[URL scheme] isequaltostring:@ "Devzeng"]) {//handling JavaScript and Objective-c interaction if ([[[URL host] isequaltostring:@ "login"]) { //Get the parameters above the URL Nsdictionary *params = [self getparams:[url query]]; BOOL status = [self login:[params objectforkey:@ "name"] password:[params objectforkey:@ "password"]; if (status) { //Call JS callback [WebView stringbyevaluatingjavascriptfromstring:@ "alert (' Login succeeded! ')"]; } Else { [WebView stringbyevaluatingjavascriptfromstring:@ ' alert (' Login failed! ') "]; } } return NO; return YES; }

Description

1. Synchronous and asynchronous issues

(1) Objective-c is synchronous when invoking JavaScript code

- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script;

(2) When JavaScript calls Objective-c code, it is asynchronous.

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

2, the common JS call

(1) Get page title

NSString *title = [webview stringByEvaluatingJavaScriptFromString:@"document.title"];

(2) Get the current URL

NSString *url = [webview stringByEvaluatingJavaScriptFromString:@"document.location.href"];

3. Use of third-party libraries

https://github.com/marcuswestin/WebViewJavascriptBridge

Use case

1. Dynamically zoom all the pictures on the page

The JavaScript scripts are as follows:

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function ResizeImages() {  var myImg, oldWidth;  var maxWidth = 320;  for(i = 0; i < document.images.length; i++) { myImg = document.images[i]; if(myImg.width > maxWidth) { oldWidth = myImg.width; myImg.width = maxWidth; myImg.heith = myImg.height*(maxWidth/oldWidth); } }}

Add the following code to your iOS code:

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[WebView stringbyevaluatingjavascriptfromstring: "Script.type = ' text/javascript ';" " var myimg,oldwidth; "" var maxwidth=380; "//Scaling factor " for (I=0;i <document.images.length;i++) {"  "myimg = Document.images[i];" " oldwidth = Myimg.width; "  "myimg.width = MaxWidth;"  "Myimg.height = Myimg.height * (maxwidth/oldwidth);"  "}\"; "  "document.getElementsByTagName (' head ') [0].appendchild (script);"]; [webview stringbyevaluatingjavascriptfromstring:@ "resizeimages ();"];

JavaScript and OC Interaction in iOS

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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