WebViewImageCache

原理: 继承NSURLProtocol, 重写startLoading方法, 当SDImageCache(其他缓存框架方案类似)存在该图片时, 将其二进制数据添加到client已加载的数据中

使用方法:

[NSURLProtocol registerClass:[LJURLCacheProtocol class]];

具体实现:

//判断加载未加载过的图片
+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
 if ([request.URL.scheme isEqualToString:@"http"] || [request.URL.scheme isEqualToString:@"https"]) {
 NSString *str = request.URL.path;
 //筛选图片 且已处理过的不再处理防止无限循环
 if (([str hasSuffix:@".png"] || [str hasSuffix:@".jpg"] || [str hasSuffix:@".jpeg"] || [str hasSuffix:@".gif"])
 && ![NSURLProtocol propertyForKey:LJURLCacheProtocolKey inRequest:request]) {
 return YES;
 }
 }
 return NO;
}
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
 NSMutableURLRequest *mutableReqeust = [request mutableCopy];
 //此处可截取request重定向.(例如:更改地址,提取请求内容,或者设置里面的请求头等)
 return mutableReqeust;
}
- (void)startLoading {
 NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
 //给处理过的请求设置标记 防止递归调用
 [NSURLProtocol setProperty:@YES forKey:LJURLCacheProtocolKey inRequest:mutableReqeust];
 
 //利用SDWebImage寻找本地图片
 NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:self.request.URL];
 
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
 //获取SDImageCache本地缓存
 NSData *data = [[SDImageCache sharedImageCache] performSelector:NSSelectorFromString(@"diskImageDataBySearchingAllPathsForKey:") withObject:key];
#pragma clang diagnostic pop
 
 if (data) {
 NSURLResponse *response = [[NSURLResponse alloc] initWithURL:mutableReqeust.URL
 MIMEType:(__bridge NSString*)[NSData sd_UTTypeFromSDImageFormat:[NSData sd_imageFormatForImageData:data]]
 expectedContentLength:data.length
 textEncodingName:nil];
 [self.client URLProtocol:self
 didReceiveResponse:response
 cacheStoragePolicy:NSURLCacheStorageNotAllowed];
 
 [self.client URLProtocol:self didLoadData:data];
 [self.client URLProtocolDidFinishLoading:self];
 } else {
 //此处处理未加载过的图片请求
 NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:nil];
 self.task = [session dataTaskWithRequest:self.request];
 [self.task resume];
 }
}
- (void)stopLoading {
 if (self.task != nil) {
 [self.task cancel];
 }
}

以下是NSURLSession协议方法

#pragma mark NSURLSessionDataDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler {
 self.responseData = [[NSMutableData alloc] init];
 [[self client] URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
 
 completionHandler(NSURLSessionResponseAllow);
}
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
 [self.responseData appendData:data];
 [[self client] URLProtocol:self didLoadData:data];
}
#pragma mark NSURLSessionTaskDelegate
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(nullable NSError *)error {
 if (error) {
 [self.client URLProtocol:self didFailWithError:error];
 }else {
 UIImage *cacheImage = [UIImage sd_imageWithData:self.responseData];
 //用SDWebImage将图片缓存
 [[SDImageCache sharedImageCache] storeImage:cacheImage forKey:[[SDWebImageManager sharedManager] cacheKeyForURL:self.request.URL] toDisk:YES completion:^{
 //do something
 }];
 [self.client URLProtocolDidFinishLoading:self];
 }
}

支持WKWebView

注意:

WKWebView拦截只在第一次加载时走startLoading方法, 此时依然可以在NSURLSessionDataDelegate方法中将图片缓存到本地

WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
if (@available(iOS 11.0, *)) {
 LJWKURLSchemeHandler *handler = [[LJWKURLSchemeHandler alloc] init];
 [configuration setURLSchemeHandler:handler forURLScheme:@"ljwebimageclick"];
} else {
 // Fallback on earlier versions
}

//
// LJWKURLSchemeHandler.h
#import <Foundation/Foundation.h>
#import <WebKit/WebKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface LJWKURLSchemeHandler : NSObject<WKURLSchemeHandler>
@end
NS_ASSUME_NONNULL_END

//
// LJWKURLSchemeHandler.m
#import "LJWKURLSchemeHandler.h"
#import <SDWebImage/UIImage+MultiFormat.h>
#import <SDWebImage/SDWebImageManager.h>
@implementation LJWKURLSchemeHandler
- (void)webView:(WKWebView *)webView startURLSchemeTask:(id<WKURLSchemeTask>)urlSchemeTask API_AVAILABLE(ios(11.0)) {
 NSURLRequest *request = urlSchemeTask.request;
 NSString *urlString = [request.URL.absoluteString stringByReplacingOccurrencesOfString:@"ljwebimageclick:" withString:@""];
 NSURL *url = [NSURL URLWithString:urlString];
 //利用SDWebImage寻找本地图片
 NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:url];
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
 NSData *data = [[SDImageCache sharedImageCache] performSelector:NSSelectorFromString(@"diskImageDataBySearchingAllPathsForKey:") withObject:key];
#pragma clang diagnostic pop
 if (data){
 [self urlSchemeTask:urlSchemeTask appendLocalData:data url:url];
 } else {
 [[SDWebImageManager sharedManager] loadImageWithURL:url options:0 progress:^(NSInteger receivedSize, NSInteger expectedSize, NSURL * _Nullable targetURL) {
 
 } completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL * _Nullable imageURL) {
 [self urlSchemeTask:urlSchemeTask appendLocalData:data url:url];
 }];
 }
 
}
- (void)urlSchemeTask:(id<WKURLSchemeTask>)urlSchemeTask appendLocalData:(NSData *)data url:(NSURL *)url API_AVAILABLE(ios(11.0)){
 NSURLResponse *response = [[NSURLResponse alloc] initWithURL:url
 MIMEType:(__bridge NSString*)[NSData sd_UTTypeFromSDImageFormat:[NSData sd_imageFormatForImageData:data]]
 expectedContentLength:data.length
 textEncodingName:nil];
 [urlSchemeTask didReceiveResponse:response];
 [urlSchemeTask didReceiveData:data];
 [urlSchemeTask didFinish];
}
- (void)webView:(nonnull WKWebView *)webView
 stopURLSchemeTask:(nonnull id<WKURLSchemeTask>)urlSchemeTask API_AVAILABLE(ios(11.0)) {
}
@end