一、說明：

NSURLProtocol可以攔截任何網絡請求，包含UIWebView中發出的所有請求。但是在WKWebView中，只能攔截到最初始的請求，內嵌的資源下載攔截不到。比如通過WKWebView加載"http://www.baidu.com",則只能攔截到"http://www.baidu.com",網頁內部的資源加載攔截不到。頁面跳轉屬于最初始請求之內，可以攔截到。

二、創建NSURLProtocol的子類，通過下面的代碼注冊此協議類：

[NSURLProtocol registerClass:[MyURLProtocol class]];

三、下面是此子類的代碼：

#import "MyURLProtocol.h"

#define MyURLProtocolHandled @"MyURLProtocolHandled"

//創建archive數據模型，重寫編碼解碼協議

@interface MyCacheData : NSObject

@property(nonatomic,strong) NSURLRequest *request;

@property(nonatomic,strong) NSURLResponse *response;

@property(nonatomic,strong) NSData *data;

@end

@interface NSURLRequest (MutableCopyWorkaround)

- (id)mutableCopyWorkaround;

@end

@interface MyURLProtocol ()

@property(nonatomic,strong) NSURLConnection *connection;

@property(nonatomic,strong) NSMutableData *httpData;

@property(nonatomic,strong) NSURLResponse *response;

@end

@implementation MyURLProtocol

#pragma mark - 重寫NSURLProtocol子類方法

+ (BOOL)canInitWithRequest:(NSURLRequest *)request

{

? ? //如果此請求是攔截到請求之后，接管請求而發起的新請求，則不處理。

? ? if ([request.URL.scheme isEqualToString:@"http"] &&

? ? ? ? [request valueForHTTPHeaderField:MyURLProtocolHandled] == nil)

? ? {

? ? ? ? return YES;

? ? }

? ? return NO;

}

+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request

{

? ? return request;

}

+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a

?? ? ? ? ? ? ? ? ? ? ? toRequest:(NSURLRequest *)b

{

? ? return [super requestIsCacheEquivalent:a toRequest:b];

}

- (void)startLoading

{

? ? //如果發現已經存在此請求的緩存數據，則返回緩存數據，否則發起新的請求從服務求加載數據

? ? MyCacheData *cacheData = [NSKeyedUnarchiver unarchiveObjectWithFile:

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? [self cachePathForRequest:self.request]];

? ? if(cacheData != nil)

? ? {

? ? ? ? NSData *data = cacheData.data;

? ? ? ? NSURLResponse *response = cacheData.response;

? ? ? ? NSURLRequest *redirectRequest = cacheData.request;

?? ? ? ?

? ? ? ? //使用NSURLProtocolClient做請求轉向，直接將請求和數據轉發到之前的請求

? ? ? ? if(redirectRequest != nil)

? ? ? ? {

? ? ? ? ? ? [[self client] URLProtocol:self wasRedirectedToRequest:redirectRequest

? ? ? ? ? ? ? ? ? ? ? redirectResponse:response];

? ? ? ? }

? ? ? ? else

? ? ? ? {

? ? ? ? ? ? [[self client] URLProtocol:self didReceiveResponse:response

? ? ? ? ? ? ? ? ? ? cacheStoragePolicy:NSURLCacheStorageNotAllowed];

? ? ? ? ? ? [[self client] URLProtocol:self didLoadData:data];

? ? ? ? ? ? [[self client] URLProtocolDidFinishLoading:self];

? ? ? ? }

? ? }

? ? else

? ? {

//接管此網絡請求，發起一個新的請求，后續會將新請求拿到的數據交給之前的舊請求

? ? ? ? NSMutableURLRequest *connectionRequest = [[self request] mutableCopyWorkaround];

? ? ? ? //增加標記，標示是由我們接管而發出的請求

? ? ? ? [connectionRequest setValue:@"Tag" forHTTPHeaderField:MyURLProtocolHandled];

? ? ? ? self.connection = [NSURLConnection connectionWithRequest:connectionRequest

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? delegate:self];

? ? }

}

- (void)stopLoading

{

? ? [self.connection cancel];

? ? self.connection = nil;

}

#pragma mark - 網絡請求代理

- (NSURLRequest *)connection:(NSURLConnection *)connection

?? ? ? ? ? ? willSendRequest:(NSURLRequest *)request

? ? ? ? ? ? redirectResponse:(NSURLResponse *)response

{

? ? if(response != nil)

? ? {

? ? ? ? NSMutableURLRequest *redirectableRequest = [request mutableCopyWorkaround];

?? ? ? ?

? ? ? ? //緩存數據

? ? ? ? MyCacheData *cacheData = [MyCacheData new];

? ? ? ? [cacheData setData:self.httpData];

? ? ? ? [cacheData setResponse:response];

? ? ? ? [cacheData setRequest:redirectableRequest];

?? ? ? ?

? ? ? ? [NSKeyedArchiver archiveRootObject:cacheData

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? toFile:[self cachePathForRequest:[self request]]];

?? ? ? ?

? ? ? ? //將請求和緩存的響應數據轉向到之前的請求

? ? ? ? [[self client] URLProtocol:self wasRedirectedToRequest:redirectableRequest

? ? ? ? ? ? ? ? ? redirectResponse:response];

? ? ? ? return redirectableRequest ;

? ? }

? ? return request;

}

- (BOOL)connectionShouldUseCredentialStorage:(NSURLConnection *)connection

{

? ? return YES;

}

- (void)connection:(NSURLConnection *)connection

didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge

{

? ? [self.client URLProtocol:self didReceiveAuthenticationChallenge:challenge];

}

- (void)connection:(NSURLConnection *)connection

didCancelAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge

{

? ? [self.client URLProtocol:self didCancelAuthenticationChallenge:challenge];

}

- (void)connection:(NSURLConnection *)connection

didReceiveResponse:(NSURLResponse *)response

{

? ? //保存響應對象

? ? self.response = response;

? ? [self.client URLProtocol:self didReceiveResponse:response

? ? ? ? ? cacheStoragePolicy:NSURLCacheStorageNotAllowed];

}

- (void)connection:(NSURLConnection *)connection

? ? didReceiveData:(NSData *)data

{

? ? [self.client URLProtocol:self didLoadData:data];

?? ?

? ? //保存服務器返回的數據

? ? if(self.httpData == nil) {

? ? ? ? self.httpData = [NSMutableData dataWithData: data];

? ? }

? ? else

? ? {

? ? ? ? [self.httpData appendData:data];

? ? }

}

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection

? ? ? ? ? ? ? ? ? willCacheResponse:(NSCachedURLResponse *)cachedResponse

{

? ? return cachedResponse;

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

? ? [self.client URLProtocolDidFinishLoading:self];

?? ?

? ? //請求加載完畢之后，將數據緩存

? ? MyCacheData *cacheData = [MyCacheData new];

? ? [cacheData setData:self.httpData];

? ? [cacheData setResponse:self.response];

? ? [NSKeyedArchiver archiveRootObject:cacheData

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? toFile:[self cachePathForRequest:self.request]];

?? ?

? ? self.connection = nil;

? ? self.httpData = nil;

? ? self.response = nil;

}

- (void)connection:(NSURLConnection *)connection

? didFailWithError:(NSError *)error

{

? ? [self.client URLProtocol:self didFailWithError:error];

?? ?

? ? self.connection = nil;

? ? self.httpData = nil;

? ? self.response = nil;

}

#pragma mark - 為請求創建緩存路徑

- (NSString *)cachePathForRequest:(NSURLRequest *)aRequest

{

? ? NSString *cachesPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory,

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? NSUserDomainMask, YES) lastObject];

? ? return [cachesPath stringByAppendingPathComponent:

? ? ? ? ? ? [NSString stringWithFormat:@"%ld", [[[aRequest URL] absoluteString] hash]]];

}

@end

@implementation NSURLRequest (MutableCopyWorkaround)

- (id) mutableCopyWorkaround {

? ? NSMutableURLRequest *mutableURLRequest = [[NSMutableURLRequest alloc]

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? initWithURL:[self URL]

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? cachePolicy:[self cachePolicy]

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? timeoutInterval:[self timeoutInterval]];

? ? [mutableURLRequest setAllHTTPHeaderFields:[self allHTTPHeaderFields]];

? ? return mutableURLRequest;

}

@end

@implementation MyCacheData

-(id) initWithCoder:(NSCoder *) aDecoder

{

? ? self = [super init];

? ? if(!self) {

? ? ? ? return nil;

? ? }

? ? [self setData:[aDecoder decodeObjectForKey:@"data"]];

? ? [self setRequest:[aDecoder decodeObjectForKey:@"request"]];

? ? [self setResponse:[aDecoder decodeObjectForKey:@"response"]];

?? ?

? ? return self;

}

- (void)encodeWithCoder:(NSCoder *)aCoder

{

? ? [aCoder encodeObject:[self data] forKey:@"data"];

? ? [aCoder encodeObject:[self request] forKey:@"request"];

? ? [aCoder encodeObject:[self response] forKey:@"response"];

}

@end

部分代碼轉自：http://tanlimin201.blog.163.com/blog/static/38171407201383032914736/

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