Injecting local files into UIWebView without breaking links - html

Question

I am working on an iOS app that needs to display webpages from a server inside a UIWebView while injecting relevant local png and css files as needed in order to speed up load time. Here is the code I am using to try to do this:
NSData *myFileData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"http://www.example.com/index.html"]]];
NSString* myFileHtml = [[NSString alloc] initWithData:myFileData encoding:NSASCIIStringEncoding];
[myWebView loadHTMLString:myFileHtml baseURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] bundlePath]]];
My problem is that some of the webpages have buttons in them that link to other webpages on the server, and because the UIWebView is only loading a string, the buttons when tapped don't cause the UIWebView to load the new webpage URL like it would if I had used the loadRequest method.
My question is how can I get the the UIWebView to behave like it is loading a request while still injecting local files from the baseurl?
Thanks

Answer 1

The relative links in the button cannot work, because the linked pages are on a remote server and not on the device's file system. However you can use a UIWebViewDelegate method to make it work:
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
if (navigationType == UIWebViewNavigationTypeLinkClicked) {
NSString *localRootPath = [NSString stringWithFormat:#"file://%#", [[NSBundle mainBundle] bundlePath]];
NSString *remoteRootPath = #"http://yourdomain.com";
NSString *remotePath = [[request.URL absoluteString] stringByReplacingOccurrencesOfString:localRootPath withString:remoteRootPath];
[self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:remotePath]]];
// or you can use your own loading mechanism here
return NO;
}
return YES;
}
This method intercepts all requests from your WebView. If the request was triggered by a user tap / click the URL gets modified from a relative URL to a absolute URL so it can be loaded from the server. Don't forget to set the delegate on the WebView or this method will not be called.

Answer 2

NSURLPRotocol is a handler for NSURLConnection and will give you the opportunity to intercept the calls to the server and substitute your own content.
1) Derive a class from NSURlProtocol
2) Call NSURLProtocol registerClass: in your application:didFinishLaunchingWithOption
3) Read the documentation on implement these methods as necessary:
initWithRequest:cachedResponse:client:,
startLoading,
URLProtocol:didReceiveResponse:cacheStoragePolicy:
URLProtocolDidFinishLoading: