覆蓋UIWebView用戶代理 - 但不適用於Facebook SDK

Question

我按照this other question中的說明在我的應用中爲webviews設置了自定義UserAgent。具體而言，我正在設置

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

在應用程序啓動時。 （只需爲UIWebView使用的NSMutableURLRequest設置適當的頭文件 - UserAgent，User-Agent，User_Agent - 不起作用。）

這會導致我的嵌入式webviews使用正確的用戶代理。但是，它也打破了Facebook SDK用於對話框的嵌入式網頁瀏覽 - 例如，在發佈到我的牆上之後，FB對話框webview的內容被替換爲文本類似於window.location.href="fbconnect:\/\/success?post_id=100002469633196_43677789308119...，並且webview未關閉通常會（用戶必須手動關閉它）。這隻發生在我設置了自定義用戶代理時。

我想我可以通過在Facebook調用並重置之前取消設置用戶代理來避開這個問題，但似乎我無法取消默認的默認設置;我在每次Facebook調用之前嘗試呼叫[[NSUserDefaults standardUserDefaults] removeObjectForKey:@"UserAgent"]和[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:NSRegistrationDomain]，並在調用的結果處理程序中再次設置它們，但我仍然看到相同的錯誤行爲。

我想我的切換初始設置[[NSUserDefaults standardUserDefaults] setObject:newUA forKey:@"UserAgent"];，但隨後我網頁視圖不拿起用戶代理。

當然，有人已經在使用非Facebook嵌入式網頁瀏覽的應用程序之前使用過Facebook SDK。我錯過了什麼？我在這方面進行了多輪討論，每一個似乎都能解決所有問題。

Answer 1

我最終不得不通過實現NSURLProtocol子類來做到這一點。雖然我的實現很麻煩，但我在下面包含了一個經過修改的版本，因爲我很驚訝，無法在StackOverflow上找到一個示例。

#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，協議必須與[NSURLProtocol registerClass:[MyProtocol class]];你做之前的任何Web請求，你想讓它適用登記 - 例如，在applicationDidFinishLaunchingWithOptions:。