覆盖UIWebView用户代理 - 但不适用于Facebook SDK

Question

我按照this other question中的说明在我的应用中为webviews设置了自定义UserAgent。具体而言，我正在设置

NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"MyApp/MyLongVersionInfoString", @"UserAgent", nil]; 
[[NSUserDefaults standardUserDefaults] registerDefaults:dictionary]; 

在应用程序启动时。 （只需为UIWebView使用的NSMutableURLRequest设置适当的头文件 - UserAgent，User-Agent，User_Agent - 不起作用。）

这会导致我的嵌入式webviews使用正确的用户代理。但是，它也打破了Facebook SDK用于对话框的嵌入式网页浏览 - 例如，在发布到我的墙上之后，FB对话框webview的内容被替换为文本类似于window.location.href="fbconnect:\/\/success?post_id=100002469633196_43677789308119...，并且webview未关闭通常会（用户必须手动关闭它）。这只发生在我设置了自定义用户代理时。

我想我可以通过在Facebook调用并重置之前取消设置用户代理来避开这个问题，但似乎我无法取消默认的默认设置;我在每次Facebook调用之前尝试呼叫[[NSUserDefaults standardUserDefaults] removeObjectForKey:@"UserAgent"]和[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:NSRegistrationDomain]，并在调用的结果处理程序中再次设置它们，但我仍然看到相同的错误行为。

我想我的切换初始设置[[NSUserDefaults standardUserDefaults] setObject:newUA forKey:@"UserAgent"];，但随后我网页视图不拿起用户代理。

当然，有人已经在使用非Facebook嵌入式网页浏览的应用程序之前使用过Facebook SDK。我错过了什么？我在这方面进行了多轮讨论，每一个似乎都能解决所有问题。

Answer 1

我最终不得不通过实现NSURLProtocol子类来做到这一点。虽然我的实现很麻烦，但我在下面包含了一个经过修改的版本，因为我很惊讶，无法在StackOverflow上找到一个示例。

#import <Foundation/Foundation.h> 

@interface MyProtocol : NSURLProtocol { 
    NSURLConnection *connection; 
} 

@property (nonatomic, retain) NSURLConnection *connection; 

@end 

@implementation MyProtocol 

@synthesize connection; 

#pragma mark - 
#pragma mark custom methods 

+ (NSString *)myUA { 
    return [[NSUserDefaults standardUserDefaults] stringForKey:@"MyCustomUserAgent"]; 
} 
+ (BOOL)canInitWithRequest:(NSURLRequest *)request 
{ 
    NSString *scheme = [request.URL.scheme stringByAppendingString:@"://"]; 
    NSString *baseRequestString = [[[request.URL absoluteString] stringByReplacingOccurrencesOfString:request.URL.path withString:@""] 
            stringByReplacingOccurrencesOfString:scheme withString:@""]; 
    if (request.URL.query != nil) { 
     NSString *query = [@"?" stringByAppendingString:request.URL.query]; 
     baseRequestString = [baseRequestString stringByReplacingOccurrencesOfString:query withString:@""]; 
    } 

    BOOL shouldIntercept = [baseRequestString isEqualToString:myWebHost]; 
    BOOL alreadyIntercepted = [[NSURLProtocol propertyForKey:@"UserAgent" inRequest:request] isEqualToString:[self myUA]]; 
    return shouldIntercept && !alreadyIntercepted; 
} 

+ (NSURLRequest *) canonicalRequestForRequest:(NSURLRequest *)request 
{ 
    return request; 
} 

- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id<NSURLProtocolClient>)client 
{ 
    NSMutableURLRequest *mutableRequest = [NSMutableURLRequest requestWithURL:request.URL 
                 cachePolicy:request.cachePolicy 
                timeoutInterval:request.timeoutInterval]; 
    [mutableRequest setAllHTTPHeaderFields:[request allHTTPHeaderFields]]; 
    [mutableRequest setHTTPMethod:[request HTTPMethod]]; 
    if ([request HTTPBody] != nil) 
     [mutableRequest setHTTPBody:[request HTTPBody]]; 
    if ([request HTTPBodyStream] != nil) 
     [mutableRequest setHTTPBodyStream:[request HTTPBodyStream]]; 
    [NSURLProtocol setProperty:[[self class] myUA] forKey:@"UserAgent" inRequest:mutableRequest]; 
    [mutableRequest setValue:[[self class] myUA] forHTTPHeaderField:@"User-Agent"]; 
    [mutableRequest setValue:[[self class] myUA] forHTTPHeaderField:@"User_Agent"]; 

    self = [super initWithRequest:mutableRequest cachedResponse:cachedResponse client:client]; 
    return self; 
} 

- (void) dealloc 
{ 
    [connection release]; 
} 

#pragma mark - 
#pragma mark boilerplate NSURLProtocol subclass requirements 

- (void) startLoading 
{ 
    self.connection = [[NSURLConnection connectionWithRequest:[self request] delegate:self] retain]; 
} 

- (void)stopLoading 
{ 
    [self.connection cancel]; 
} 

- (void)connection:(NSURLConnection*)conn didReceiveResponse:(NSURLResponse*)response 
{ 
    [[self client] URLProtocol:self didReceiveResponse:response cacheStoragePolicy:[[self request] cachePolicy]]; 
} 

- (void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data 
{ 
    [[self client] URLProtocol:self didLoadData:data]; 
} 

- (void)connectionDidFinishLoading:(NSURLConnection*)conn 
{ 
    [[self client] URLProtocolDidFinishLoading:self]; 
} 

- (NSURLRequest*)connection:(NSURLConnection*)connection willSendRequest:(NSURLRequest*)theRequest redirectResponse:(NSURLResponse*)redirectResponse 
{ 
    return theRequest; 
} 

- (void)connection:(NSURLConnection*)conn didFailWithError:(NSError*)error 
{ 
    [[self client] URLProtocol:self didFailWithError:error]; 
} 

@end 

注意，协议必须与[NSURLProtocol registerClass:[MyProtocol class]];你做之前的任何Web请求，你想让它适用登记 - 例如，在applicationDidFinishLaunchingWithOptions:。