iPhone SDK: Firing custom events when a link is clicked in a UIWebView

1:41:00 PM |

Start by opening up the WebBrowserTutorialAppDelegate.h file and editing the@interface line to read:
@interface WebBrowserTutorialAppDelegate : NSObject <UIWebViewDelegate> {
What we have done is to make the main AppDelegate a delegate for the UIWebView as well.
Now we need to set our webView to have the main AppDelegate as its delegate, you can do this by opening up WebBrowserTutorialAppDelegate.m and putting the following line just inside the applicationDidFinishLaunching function:
webView.delegate = self;
That is all pretty self explanatory, it just sets the delegate of our webView to self, which in this case is our main application delegate.
Now we are pretty much done, we just need to add the function to catch the link clicks. To do this we need to add a new function, copy the content below to the WebBrowserTutorialAppDelegate.m file:
- (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType {
NSURL *url = request.URL;
NSString *urlString = url.absoluteString;
return YES;
This function will catch all requests and allow you to either manipulate them and pass them on or to perform your own custom action and stop the event from bubbling.
The first line gets the URL of the request, this is the contents inside the href attribute in the anchor tag.
The next line converts the URL to a string so we can log it out. You can access many parts of the NSURL, here are some of them and brief description of what they do.
absoluteString – An absolute string for the URL. Creating by resolving the receiver’s string against its base.
absoluteURL – An absolute URL that refers to the same resource as the receiver. If the receiver is already absolute, returns self.
baseURL – The base URL of the receiver. If the receiver is an absolute URL, returns nil.
host – The host of the URL.
parameterString – The parameter string of the URL.
password – The password of the URL (i.e. http://user:pass@www.test.com would return pass)
path – Returns the path of a URL.
port – The port number of the URL.
query – The query string of the URL.
relativePath – The relative path of the URL without resolving against the base URL. If the receiver is an absolute URL, this method returns the same value as path.
relativeString – string representation of the relative portion of the URL. If the receiver is an absolute URL this method returns the same value as absoluteString.
scheme – The resource specifier of the URL (i.e. http, https, file, ftp, etc).
user – The user portion of the URL.
Then the third line simply logs the URL to the console, so you will new to open up the console while you run this in the simulator to see the results.
Finally the forth line returns YES, this will allow the UIWebView to follow the link, if you would just like to catch a link and stop the UIWebView from following it then simply return NO.