增强UIWebView的cache

尝试了一下增强UIWebView的cache。不过实际效果并不理想。即便有cache，消除了从新联网请求都时间，但是重新排版时间仍然很长。UIWebView对前进后退都响应速度没明显改善。

 

这里介绍简单粗暴的利用文件系统增加cache的方法。

 

基本原理是继承NSURLCache，并替换默认NSURLCache实例。在发现cache未命中都时候，去请求cache内容。因为UIWebView并不返回所有内容给NSURLCache。具体可以自己跟踪一下里面保存cache的方法。UIWebView每请求一个页面，只会存一次cache，即页面都cache。其他图片，css，js都不会保存。而且实际上也没进内存，NSURLCache默认都实现貌似是抛弃了结果。因为每次从新查询cache都是空返回。

 

这里基于AISHTTPRequest，这样不需要自己写队列和处理cookie。

可以去这里下http://allseeing-i.com/ASIHTTPRequest/

很好很强大都开源代码

 

也可以用NSData直接通过url请求，不过这样出了要考虑cookie以外，靠多线程处理会需要一下开很多线程，要么自己写队列。

 

顺便鄙视一下csdn插入代码不支持objectiv c

 

继承NSURLCache

 

#import <Foundation/Foundation.h>#import <Foundation/NSURLCache.h>#import "ASIHTTPRequestDelegate.h"// just a fack cache to record the cache request@interface VURLCache : NSURLCache <ASIHTTPRequestDelegate> {int found;int missed;}-(BOOL) shouldBlockFileCache:(NSURLRequest*) request;-(NSString*) cacheFilePath:(NSURLRequest*) request;-(NSCachedURLResponse*) loadCacheFromFile:(NSURLRequest*) request;@end 

 

实现文件cache

//// VURLCache.m// CacheTestSample//// Created by apple on 10-11-16.// Copyright 2010 __MyCompanyName__. All rights reserved.//#import "VURLCache.h"#import "ASIHTTPRequest.h"#import <Foundation/NSURLRequest.h>@implementation VURLCache//- (NSCachedURLResponse*)cachedResponseForRequest:(NSURLRequest *)request {//NSLog( @"req cache for %@", [[request URL] description] );//NSLog( @"main dom url %@", [[request mainDocumentURL] description]);//NSCachedURLResponse* rep = [super cachedResponseForRequest: request];//return rep;//}////- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request {//NSLog( @"store cache for %@", [[request URL] description] );//[super storeCachedResponse:cachedResponse forRequest:request];//}#pragma mark NSURLCache- (id)initWithMemoryCapacity:(NSUInteger)memoryCapacity diskCapacity:(NSUInteger)diskCapacity diskPath:(NSString *)path {self = [super initWithMemoryCapacity:memoryCapacity diskCapacity:diskCapacity diskPath:path];found = 0;missed = 0;return self;}-(NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {//NSLog( @"request cache for %@", [[request URL] description] );NSCachedURLResponse* cacheResponse = [super cachedResponseForRequest: request];if( nil != cacheResponse ) {found++;// NSLog(@"got cache from NSURLCache");// NSLog(@"found %d missed %d", found, missed);return cacheResponse;}if( [self shouldBlockFileCache:request] ) {// NSLog(@"block from file cache");missed++;// NSLog(@"found %d missed %d", found, missed);return nil;}cacheResponse = [self loadCacheFromFile:request];if( nil == cacheResponse ) {missed++;} else {found++;}// NSLog(@"found %d missed %d", found, missed);return cacheResponse;}#pragma mark -#pragma mark disk cache afx-(NSString*) cacheFilePath:(NSURLRequest*) request {// parse urlNSURL* url = request.URL;// the top path is host nameNSString* host = url.host;// create hash code according to the reletive pathNSString* relUrl = url.relativePath;NSUInteger hash = [relUrl hash];NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); //NSLog(@"PATH S%@", paths); NSString *documentsDirectory = [paths objectAtIndex:0];NSString* storagePath = [NSString stringWithFormat:@"%@/cache/%@/%08x", documentsDirectory, host, hash];// storagePath is auto releasereturn storagePath;}-(NSCachedURLResponse*) loadCacheFromFile:(NSURLRequest*) request {NSCachedURLResponse* cacheResponse = nil;NSString* storagePath = [self cacheFilePath:request];if( nil == storagePath ) {return cacheResponse;}NSString* dataPath = [storagePath stringByAppendingString:@"/data"];NSString* mimePath = [storagePath stringByAppendingString:@"/mime"];NSString* encodingPath = [storagePath stringByAppendingFormat:@"/encoding"];if ([[NSFileManager defaultManager] fileExistsAtPath:dataPath]) {NSLog(@"CACHE FOUND for %@", request.URL.relativePath);NSData* content = [NSData dataWithContentsOfFile:dataPath];NSData* mimeData = [NSData dataWithContentsOfFile:mimePath];NSData* encodingData = [NSData dataWithContentsOfFile:encodingPath];NSString* mime = nil;if( nil != mimeData ) {mime = [[NSString alloc] initWithData:mimeData encoding:NSUTF8StringEncoding];} else {mime = @"";}NSString* encoding = nil;if( nil != encodingData ) {encoding = [[NSString alloc] initWithData:encodingData encoding:NSUTF8StringEncoding];}NSURLResponse* response = [[NSURLResponse alloc] initWithURL:request.URL MIMEType:mime expectedContentLength:[content length] textEncodingName:encoding];cacheResponse = [[NSCachedURLResponse alloc] initWithResponse:response data:content];} else {//trick here : if no cache, populate it asynchronously and return nilNSLog(@"download CACHE for %@", request.URL.relativePath);// [NSThread detachNewThreadSelector:@selector(populateCacheFor:) toTarget:self withObject:request];NSURL *url = request.URL;ASIHTTPRequest *asirequest = [ASIHTTPRequest requestWithURL:url];asirequest.argObj = request;[asirequest setDelegate:self];[asirequest startAsynchronous];}return cacheResponse;}-(BOOL) shouldBlockFileCache:(NSURLRequest*) request {NSURL* url = request.URL;if( nil == url.host || 0 == url.host.length ) {// block the request without hostreturn YES;}if( nil != url.user || nil != url.password ) {// block the request with securityreturn YES;}// check the file typeNSString* ressourceName = url.relativePath; //we're only caching the following files if ([ressourceName rangeOfString:@".png"].location!=NSNotFound || [ressourceName rangeOfString:@".jp"].location!=NSNotFound ||[ressourceName rangeOfString:@".gif"].location!=NSNotFound ||[ressourceName rangeOfString:@".tif"].location!=NSNotFound || [ressourceName rangeOfString:@".js"].location!=NSNotFound ||[ressourceName rangeOfString:@".css"].location!=NSNotFound ||[ressourceName rangeOfString:@".cgz"].location!=NSNotFound || [ressourceName rangeOfString:@".jgz"].location!=NSNotFound) {return NO;}return YES;}#pragma mark -#pragma mark ASIHTTPRequestDelegate- (void)requestFinished:(ASIHTTPRequest *)request {NSString* storagePath = [self cacheFilePath: request.argObj];NSData* content = [request responseData];NSString* contentType = [[request responseHeaders] objectForKey:@"Content-Type"];NSString* mime = nil;NSString* encoding = nil;// split contentTypeNSRange sepRange = [contentType rangeOfString:@"; "];if( sepRange.location != NSNotFound ) {// sep the content typemime = [contentType substringToIndex: sepRange.location];// get text encodingencoding = [contentType substringFromIndex: (sepRange.location + sepRange.length)];} else {mime = contentType;}NSError* error = nil;//the store is invoked automatically.[[NSFileManager defaultManager] createDirectoryAtPath:storagePath withIntermediateDirectories:YES attributes:nil error:&error];BOOL ok;// = [[NSFileManager defaultManager] createDirectoryAtPath:absolutePath withIntermediateDirectories:YES attributes:nil error:&error];NSString* dataPath = [storagePath stringByAppendingString:@"/data"];ok = [content writeToFile:dataPath atomically:YES];//NSLog(@"Caching %@ : %@", dataPath , ok?@"OK":@"KO");if( ok ) {//save mime and encodingif( nil != mime ) {error = nil;NSString* mimePath = [storagePath stringByAppendingString:@"/mime"];[mime writeToFile:mimePath atomically:YES encoding:NSUTF8StringEncoding error:&error];}if( nil != encoding ) {error = nil;NSString* encodingPath = [storagePath stringByAppendingFormat:@"/encoding"];[encoding writeToFile:encodingPath atomically:YES encoding:NSUTF8StringEncoding error:&error];}} }#pragma mark -@end 

 

UIWebView会通过cachedResponseForRequest方法查询cache。

这时候可以提交我们自己的cache。

同时，如果cache没有命中，可以利用传入的NSURLRequest发送请求。

这里利用了ASIHTTPRequest的异步方法，发送请求。

 

为了利用ASIHTTPRequest都队列，还修改了一下这个类，增加了一个引用，记录了对应都NSURLRequest。

这样在回调requestFinished方法时，就能知道是那个请求，保存cache。

 

最后去AppDelegate里替换掉全局的NSURLCache

// Override point for customization after app launch. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *docDir = [paths objectAtIndex:0]; NSString *path = docDir; // the path to the cache file NSUInteger discCapacity = 0; NSUInteger memoryCapacity = 5120*1024;// create cache file poolNSString* diskCachePath = [NSString stringWithFormat:@"%@/%@", docDir, @"cache"];NSError* error; [[NSFileManager defaultManager] createDirectoryAtPath:diskCachePath withIntermediateDirectories:YES attributes:nil error:&error];// add extended cache pool for all browser VURLCache *cache = [[VURLCache alloc] initWithMemoryCapacity:memoryCapacity diskCapacity:discCapacity diskPath:path]; [NSURLCache setSharedURLCache:cache]; [cache release]; 

 

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