我有一个 UIWebView 和一个自定义 NSURLProtocol 类注册到代理 HTTP 请求。我在加载 github.com 时遇到问题。如果我浏览到https://github.com,那么它会很好地加载页面及其内容。但是,如果我浏览到http://github.com,它会正确加载 HTML,但不会加载图像或 CSS。这是我加载 https 版本时的样子:
这是我加载 http 版本时的样子:
这是我用来重现此问题的视图控制器的代码:
@interface ViewController ()
{
UIWebView *aWebView;
}
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[NSURLProtocol registerClass:[WebViewProxyURLProtocol class]];
aWebView = [[UIWebView alloc] initWithFrame:self.view.frame];
aWebView.delegate = self;
[self.view addSubview:aWebView];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://github.com"]];
[aWebView loadRequest:request];
}
@end
这是 NSURLProtocol 的实现:
@interface WebViewProxyURLProtocol : NSURLProtocol <NSURLConnectionDataDelegate>
@end
@implementation WebViewProxyURLProtocol {
NSMutableURLRequest* correctedRequest;
}
+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
return ([[request allHTTPHeaderFields] objectForKey:@"X-WebViewProxy"] == nil);
}
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
return request;
}
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b {
return NO;
}
- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id<NSURLProtocolClient>)client {
if (self = [super initWithRequest:request cachedResponse:cachedResponse client:client]) {
// Add header to prevent loop in proxy
correctedRequest = request.mutableCopy;
[correctedRequest addValue:@"True" forHTTPHeaderField:@"X-WebViewProxy"];
}
return self;
}
- (void)startLoading {
[NSURLConnection connectionWithRequest:correctedRequest delegate:self];
}
- (void)stopLoading {
correctedRequest = nil;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[self.client URLProtocol:self didLoadData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[self.client URLProtocolDidFinishLoading:self];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
[self.client URLProtocol:self didFailWithError:error];
}
- (NSURLRequest *)connection:(NSURLConnection *)connection
willSendRequest:(NSURLRequest *)request
redirectResponse:(NSURLResponse *)redirectResponse
{
return request;
}
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
return nil;
}
@end
如果我禁用自定义 NSURLProtocol 类,它工作正常。我使用 Charles 来检查 HTTP 请求和响应,无论是否使用 NSURLProtocol,它们看起来都相同。
那么问题来了:为什么UIWebView在使用NSURLConnection获取页面数据的时候不请求网页的内容呢?