拦截webP的网络请求，利用SDWebImage进行转码，然后加载

//
//  WebPLoadProtocol.m
//  WCFriend
//
//  Created by apple on 2016/11/18.
//  Copyright © 2016年 apple. All rights reserved.
//

/*
 
 在需要加载webP的控制器加入此句
 [NSURLProtocol registerClass:[WebPLoadProtocol class]];
 
 */

#import "WebPLoadProtocol.h"
#import "UIImage+WebP.h"

static NSString *URLProtocolHandledKey = @"URLHasHandle";

@interface WebPLoadProtocol ()<NSURLSessionDelegate>

@property(nonatomic, strong) NSURLSession *session;

@end

@implementation WebPLoadProtocol

#pragma mark - 初始化请求

+ (BOOL)canInitWithRequest:(NSURLRequest *)request
{
    //只处理http和https请求
    NSString *scheme = [[request URL] scheme];
    if ( ([scheme caseInsensitiveCompare:@"http"] == NSOrderedSame ||
          [scheme caseInsensitiveCompare:@"https"] == NSOrderedSame))
    {
        if ([NSURLProtocol propertyForKey:URLProtocolHandledKey inRequest:request]) {
            return NO;
        }
        return YES;
    }
    return NO;
}

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

#pragma mark - 通信协议内容实现

- (void)startLoading
{
    NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
    //标示改request已经处理过了，防止无限循环
    [NSURLProtocol setProperty:@YES forKey:URLProtocolHandledKey inRequest:mutableReqeust];
    
    if (![[self.request.URL absoluteString] hasSuffix:@"webp"]) {
        
        NSLog(@"是一个正常的,%@",self.request.URL);
        
    }else{
        NSLog(@"检测到了 webp---%@,拦截它",self.request.URL);
    }
    
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    self.session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue currentQueue]];
    [[self.session dataTaskWithRequest:mutableReqeust] resume];
    
}

- (void)stopLoading
{
    [self.session invalidateAndCancel];
}

#pragma mark dataDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
{
    [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    
    if (completionHandler) {
        completionHandler(NSURLSessionResponseAllow);
    }
    
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{
    
    NSData *transData = data;
    
    if ([dataTask.currentRequest.URL.absoluteString hasSuffix:@"webp"]) {
        NSLog(@"webp---%@---替换它",dataTask.currentRequest.URL);
        //采用 SDWebImage 的转换方法
        UIImage *imgData = [UIImage sd_imageWithWebPData:data];
        transData = UIImageJPEGRepresentation(imgData, 1.0f);
    }
    
    [self.client URLProtocol:self didLoadData:transData];
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(nullable NSError *)error{
    
    if (error) {
        
        [self.client URLProtocol:self didFailWithError:error];
    }else{
        
        [self.client URLProtocolDidFinishLoading:self];
    }
    
}
@end