calling javascript objective-c without visible uiwebview

Question

I want to call javascript functions from my objective-c. This for iphone. I understand how the call to the javascript function is done with this line

NSString *returnValue = [webView stringByEvaluatingJavascriptFromString:method];

But I dont actually want a webview to be seen or used as part of the UI. So can I just create an instance of it right before calling the method above in some way.

I have tried:

UIWebView *webView = [[UIWebView alloc]initWithFrame:CGRectZero];
[webView loadRequest:[NSUrLRequest requestWithUrl:url]];

but nothing seems to happen. So is there a method similar to the above that I am meant to use.

Adding it to the view is not the main issue. See my answer for the full solution. — james_womack
– james_womack, Commented Jul 9, 2013 at 10:18

Vame · Accepted Answer · 2013-07-09 10:16:13Z

1

add the webview in your controller's view in order to run the javascript. it won't be visible since it has zero height and width.

edited Jul 9, 2013 at 10:16

answered Jul 9, 2013 at 10:11

Vame

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7 Comments

walsh06 Over a year ago

I added it to the view before thinking something like that would happen but I got the error "application windows are expected to have a root view controller"

Vame Over a year ago

where did you try to add it? you should do this inside a view controller. [self addSubview:web view];

walsh06 Over a year ago

I must have done something wrong earlier as I tried it again and it worked this time. So thanks for the help.

walsh06 Over a year ago

Sorry slight follow up question but my returnValue is not taking a NSString as the result. Do you know why this might be?? In the console it says @<variable is not NSString>

Vame Over a year ago

Return Value: The result of running script or nil if it fails. Cross check it. it might be nil.

|

james_womack · Accepted Answer · 2013-07-09 10:38:31Z

0

Your issue is not related to the size of the UIWebView. It is simply a timing issue. The following code works as desired with a zero rect UIWebView instance. Note the use of UIWebViewDelegate method webViewDidFinishLoad:. UIWebView is slow and it takes time for the view to load its content and be prepared to accept JavaScript commands.

@interface NGViewController () <UIWebViewDelegate>
@property (nonatomic, strong) UIWebView *hiddenWebView;
@end

@implementation NGViewController

@synthesize hiddenWebView = _hiddenWebView;

- (void)viewWillLayoutSubviews
{
  [super viewWillLayoutSubviews];

  if (!self.hiddenWebView.superview)
  {
    [self.view addSubview:self.hiddenWebView];
  }
}

- (UIWebView *)hiddenWebView
{
  if (!_hiddenWebView) {
    _hiddenWebView = [UIWebView.alloc initWithFrame:CGRectZero];
    _hiddenWebView.delegate = self;
    [_hiddenWebView loadHTMLString:@"<html><head><script>window.james = 'My name';</script></head><body><h1>Hidden Web View by James</h1></body></html>" baseURL:nil];
  }
  return _hiddenWebView;
}

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
  NSString *documentBodyString = [self.hiddenWebView stringByEvaluatingJavaScriptFromString:@"window.james;"];
  NSLog(@"The body's inner HTML is: %@", documentBodyString);
}

@end

The output of which is:

2013-07-09 03:13:29.347 WebViewTest[14261:c07] The body's inner HTML is: My name

edited Jul 9, 2013 at 10:38

answered Jul 9, 2013 at 10:17

james_womack

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2 Comments

walsh06 Over a year ago

cannot I not just use webViewDidFinishLoad instead of manually delaying??

james_womack Over a year ago

@walsh06 — did you try it? The point is you have a timing issue, and I've provided you with a working example. I've updated the answer to show that delegate method also works.

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