一、说明：

NSURLProtocol可以拦截任何网络请求，包含UIWebView中发出的所有请求。但是在WKWebView中，只能拦截到最初始的请求，内嵌的资源下载拦截不到。比如通过WKWebView加载"http://www.baidu.com",则只能拦截到"http://www.baidu.com",网页内部的资源加载拦截不到。页面跳转属于最初始请求之内，可以拦截到。

二、创建NSURLProtocol的子类，通过下面的代码注册此协议类：

[NSURLProtocol registerClass:[MyURLProtocol class]];

三、下面是此子类的代码：

#import "MyURLProtocol.h"

#define MyURLProtocolHandled @"MyURLProtocolHandled"

//创建archive数据模型，重写编码解码协议

@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 - 重写NSURLProtocol子类方法

+ (BOOL)canInitWithRequest:(NSURLRequest *)request

{

//如果此请求是拦截到请求之后，接管请求而发起的新请求，则不处理。

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

{

//如果发现已经存在此请求的缓存数据，则返回缓存数据，否则发起新的请求从服务求加载数据

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做请求转向，直接将请求和数据转发到之前的请求

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

{

//接管此网络请求，发起一个新的请求，后续会将新请求拿到的数据交给之前的旧请求

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

//增加标记，标示是由我们接管而发出的请求

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

self.connection = [NSURLConnection connectionWithRequest:connectionRequest

delegate:self];

}

}

- (void)stopLoading

{

[self.connection cancel];

self.connection = nil;

}

#pragma mark - 网络请求代理

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

willSendRequest:(NSURLRequest *)request

redirectResponse:(NSURLResponse *)response

{

if(response != nil)

{

NSMutableURLRequest *redirectableRequest = [request mutableCopyWorkaround];

//缓存数据

MyCacheData *cacheData = [MyCacheData new];

[cacheData setData:self.httpData];

[cacheData setResponse:response];

[cacheData setRequest:redirectableRequest];

[NSKeyedArchiver archiveRootObject:cacheData

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

//将请求和缓存的响应数据转向到之前的请求

[[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

{

//保存响应对象

self.response = response;

[self.client URLProtocol:self didReceiveResponse:response

cacheStoragePolicy:NSURLCacheStorageNotAllowed];

}

- (void)connection:(NSURLConnection *)connection

didReceiveData:(NSData *)data

{

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

//保存服务器返回的数据

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];

//请求加载完毕之后，将数据缓存

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 - 为请求创建缓存路径

- (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

部分代码转自：http://tanlimin201.blog.163.com/blog/static/38171407201383032914736/