Loading resources from relative paths through NSURLProtocol subclass

问题

I have an NSURLProtocol registered for a UIWebView-based app, set up to respond to file scheme requests.

In the web view, I load images, CSS, JS etc. and all that's all working fine; the problem comes when I try to reference an image in a CSS file that's not at the root directory of the HTML tree. E.g.

<html>
    <head>
        <style type="text/css">
        .1 { background-image: url("1.png"); }
        </style>
        <link href="css/style.css" rel="stylesheet" type="text/css" />
        <!-- contents of css/style.css might be:
        .2 { background-image: url("../2.png"); }
        -->
    </head>
    <body>
        <div class="1">properly styled</div>
        <div class="2">not styled</div>
    </body>
</head>

Looking at the requests arriving at my NSURLProtocol, I can't see a way of determining where in my source tree the requesting file sits.

For example, if the above HTML was in a file called source/index.html, my NSURLProtocol subclass would get a request for ../2.png from the source/css/style.css file.

This should resolve to source/2.png, but I can't tell there should be that css subdirectory included in the path.

Is there any way to get more context about the source of a request, so that I fix up the paths when I look for the requested file?

回答1:

I had a quite similar issue, explained here: Loading resources from relative paths through NSURLProtocol subclass

I had the following in my NSURLProtocol :

- (void)startLoading {
    [self.client URLProtocol:self
          didReceiveResponse:[[NSURLResponse alloc] init]
          cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    //Some other stuff
}

and solved the issue with the following :

- (void)startLoading {
    [self.client URLProtocol:self
          didReceiveResponse:[[NSURLResponse alloc] initWithURL:_lastReqURL MIMEType:nil expectedContentLength:-1 textEncodingName:nil]
          cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    //Some other stuff
}

Where _lastReqURL is _lastReqURL = request.URL;, from

- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id < NSURLProtocolClient >)client {
    self = [super initWithRequest:request cachedResponse:cachedResponse client:client];
    if (self) {
        _lastReqURL = request.URL;
        // Some stuff
    }
}

I can only assume the URL part in NSURLResponse is critical when dealing with relative-paths (seems logical).

来源：https://stackoverflow.com/questions/11874795/loading-resources-from-relative-paths-through-nsurlprotocol-subclass

标签

ios

uiwebview

webview

nsurlprotocol