Injecting JavaScript into UIWebView

Question

I am trying to use the stringByEvaluatingJavaScriptFromString: to alter a WebView and it's not executing as I expect.

Here is the code, this JS doesn't execute though. Any idea why?

UIWebView *wv = [UIWebView alloc] init];

NSURL *url = [[NSURL alloc] initWithString:@"http://www.google.com"];

NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];

[wv loadRequest:request];

[wv stringByEvaluatingJavaScriptFromString:@"document.write('This Works')"];

phi · Accepted Answer · 2012-01-09 10:19:44Z

3

Probably you'll have to wait for the request to finish before you can use stringByEvaluatingJavaScriptFromString. Set wv.delegate = self; and then implement -webViewDidFinishLoad like this

-(void)webViewDidFinishLoad:(UIWebView *)webView {
    [webView stringByEvaluatingJavaScriptFromString:@"document.write('This Works')"];
}

answered Jan 9, 2012 at 10:19

phi

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5 Comments

Andrew Lauer Barinov Over a year ago

After I try this, the WebView goes blank and I can't see "This Works" anywhere.

A-Live Over a year ago

@Andrew Barinov, If you need to stop it, use a boolean flag. If you want to write a text to google search field, document.write is not what you are looking for.

phi Over a year ago

That's strange, it works for me. Your delegate methods are getting called properly, right?

Andrew Lauer Barinov Over a year ago

Yep, I put an NSLog into my delegate method and I see it printing on my console.

Andrew Lauer Barinov Over a year ago

@user792677 I'm actually trying to modify the structure of the page the user sees, not perform a search.

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