UIWebView注入javascript iphone

最新推荐文章于 2023-04-04 13:50:52 发布

ToddFox

最新推荐文章于 2023-04-04 13:50:52 发布

阅读量1.7k

点赞数

分类专栏： iPhone 文章标签： javascript iphone function objective c constants input

iPhone 专栏收录该内容

150 篇文章

订阅专栏

本文探讨了UIWebView中使用stringByEvaluatingJavaScriptFromString方法的强大功能，包括执行多行JavaScript代码、注入自定义函数及从HTML文档获取信息等。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

from: http://www.devdiv.com/thread-31578-1-1.html

UIWebView has very few instance methods. One of them is stringByEvaluatingJavaScriptFromString, which very powerful and unfortunately poorly documented. (This is literally the extent of Apple’s explanation: “Returns the result of running a script.”)

Let’s explore this mysterious method with a couple of examples.

A trivial example of how to use stringByEvaluatingJavaScriptFromString is to get the title of the HTML document:

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

You would typically place this line of code in webViewDidFinishLoad.

This technique is not limited to one-liners, or accessing simple properties. Here’s an example of two lines of JavaScript code executed in order, as you would expect:

[webView stringByEvaluatingJavaScriptFromString:@"var field = document.getElementById('field_2');"
"field.value='Multiple statements - OK';"];

You can also call JavaScript functions this way. And if you want to call a JavaScript function that does not already exist in the web page that you’re downloading, you can “inject” it yourself with this technique:

[webView stringByEvaluatingJavaScriptFromString:@"var script = document.createElement('script');"
"script.type = 'text/javascript';"
"script.text = \"function myFunction() { "
"var field = document.getElementById('field_3');"
"field.value='Calling function - OK';"
"}\";"
"document.getElementsByTagName('head')[0].appendChild(script);"];
[webView stringByEvaluatingJavaScriptFromString:@"myFunction();"];

In essence I’m using Objective C to create a string which represents JavaScript which which when executed adds a JavaScript function to the HTML DOM. Apologies for the multiple meta levels… Let me try to untangle this line by line.

Line 1 : First we create a <script> element using JavaScript.
Line 2 : Set the type of the <script> element to text/javascript.
Line 3-6 : Set the content of the <script> element to the JavaScript function that you want to inject.
Line 7 : Add the new <script> element as a child to the <head> element of the HTML DOM.
Line 9 : Call the new JavaScript function.

Bonus tip: You can break up NSString constants over multiple lines in Xcode for increased readability. Just end the line with a double-quote character and begin the next line with a double-quote character. At compile time these lines will be joined into one string. So the string that begins with “var script” on Line 1 is one continuous string ending with “appendChild(script);” on Line 7.

Although it’s not critical for the discussion above, here’s the HTML that the example JavaScript refers to:

01.<html>
02. <head>
03. <meta name="viewport" content="width=320; initial-scale=1.0; maximum-scale=1.0"/>
04. </head>
05. <body>
06. <p>This is the UIWebView</p>
07. <form>
08. <input id="field_1" type="text" name="value" /><br/>
09. <input id="field_2" type="text" name="value" /><br/>
10. <input id="field_3" type="text" name="value" /><br/>
11. </form>
12. </body>
13.</html>

点击页面上的一个按钮，回调到自己的Objective-c代码了

<html>
<body>
<textarea id="ttt"></textarea>
<input type="button1" value="GetSR" onClick="fn()"/>
<input type="button2" value="Download" onClick="doDownload()"/>
</body>
</html>

<script>
function fn()
{
alert("tt");
}

function doDownload()
{
var url = 'http://192.168.1.2/dj_bmw.mp3';
iPhone.downloadUrl(url);
}
</script>

页面加载完的时候调用javascript函数把页面里doDownload代码

function doDownload()
{
window.locate = '/_Custom_Lint/ var url = http://192.168.1.2/dj_bmw.mp3; iPhone.downloadUrl(url);'
}

UIWebView回调

- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request
navigation:(UIWebViewNavigationType)navigationType
{
NSString* urlString = [ [request URL] absoluteString] ;
if (urlString 包含 "/_Custom_Lint")
{
解析urlString 取出具体的下载地址（ 'http://192.168.1.2/dj_bmw.mp3'），调用本地下载代码。
return NO;
}
return YES;
}