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相信不少朋友用过UIWebView，webView下载的图片一般比较大，这个要能缓存就好了，可以大幅度提高加载速度，同时为用户节省流量。本文就是讲如何完美解决webView缓存的问题。
实际上，UIWebView自己是有缓存的，但容量有限，清理时间我们也不好掌握，那它是用什么做的缓存呢？是NSURLCache。看到它有几个方法:
+ (void)setSharedURLCache:(NSURLCache *)cache;
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request;
- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request;
太好了，我们只要写一个子类继承NSURLCache，实现后两个方法，再让这个子类对象成为sharedURLCache，就可以操控webView的请求和缓存了。抛个砖吧：
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
NSString *pathString = [[request URL] absoluteString];
if(![pathString hasSuffix:@".jpg"]) {
return[super cachedResponseForRequest:request];
}
if([[MYURLCache sharedCache] hasDataForURL:pathString]) {
NSData *data = [[MYURLCache sharedCache] dataForURL:pathString];
NSURLResponse *response = [[[NSURLResponse alloc] initWithURL:[request URL]
MIMEType:@"image/jpg"
expectedContentLength:[data length]
textEncodingName:nil] autorelease];
return[[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];
}
return[super cachedResponseForRequest:request];
}
- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request {
NSString *pathString = [[request URL] absoluteString];
if(![pathString hasSuffix:@".jpg"]) {
[super storeCachedResponse:cachedResponse forRequest:request];
return;
}
[[MYURLCache sharedCache] storeData:cachedResponse.data forURL:pathString];
}
上面的代码是专门用来搞定webView中的jpg图片的，其中MYURLCache提供了把data读、写入文件的功能，这个不是本文的重点，请各位自己实现吧。
在程序启动的时候，加入以下代码：
MYURLCache *cache = [[MYURLCache alloc] init];
[NSURLCache setSharedURLCache:cache];
OK，搞定了，试试webView加载图片吧~
//=========================//
- (id)initWithMemoryCapacity:(NSUInteger)memoryCapacity diskCapacity:(NSUInteger)diskCapacity diskPath:(NSString *)path cacheTime:(NSInteger)cacheTime {
if (self = [self initWithMemoryCapacity:memoryCapacity diskCapacity:diskCapacity diskPath:path]) {
self.cacheTime = cacheTime;
if (path)
self.diskPath = path;
else
self.diskPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
self.responseDictionary = [NSMutableDictionary dictionaryWithCapacity:0];
}
return self;
}
- (void)dealloc {
[_diskPath release];
[_responseDictionary release];
[super dealloc];
}
- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
if ([request.HTTPMethod compare:@"GET"] != NSOrderedSame) {
return [super cachedResponseForRequest:request];
}
return [self dataFromRequest:request];
}
- (void)removeAllCachedResponses {
[super removeAllCachedResponses];
[self deleteCacheFolder];
}
- (void)removeCachedResponseForRequest:(NSURLRequest *)request {
[super removeCachedResponseForRequest:request];
NSString *url = request.URL.absoluteString;
NSString *fileName = [self cacheRequestFileName:url];
NSString *otherInfoFileName = [self cacheRequestOtherInfoFileName:url];
NSString *filePath = [self cacheFilePath:fileName];
NSString *otherInfoPath = [self cacheFilePath:otherInfoFileName];
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager removeItemAtPath:filePath error:nil];
[fileManager removeItemAtPath:otherInfoPath error:nil];
}
#pragma mark - custom url cache
- (NSString *)cacheFolder {
return @"URLCACHE";
}
- (void)deleteCacheFolder {
NSString *path = [NSString stringWithFormat:@"%@/%@", self.diskPath, [self cacheFolder]];
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager removeItemAtPath:path error:nil];
}
- (NSString *)cacheFilePath:(NSString *)file {
NSString *path = [NSString stringWithFormat:@"%@/%@", self.diskPath, [self cacheFolder]];
NSFileManager *fileManager = [NSFileManager defaultManager];
BOOL isDir;
if ([fileManager fileExistsAtPath:path isDirectory:&isDir] && isDir) {
} else {
[fileManager createDirectoryAtPath:path withIntermediateDirectories:YES attributes:nil error:nil];
}
return [NSString stringWithFormat:@"%@/%@", path, file];
}
- (NSString *)cacheRequestFileName:(NSString *)requestUrl {
return [Util md5Hash:requestUrl];
}
- (NSString *)cacheRequestOtherInfoFileName:(NSString *)requestUrl {
return [Util md5Hash:[NSString stringWithFormat:@"%@-otherInfo", requestUrl]];
}
- (NSCachedURLResponse *)dataFromRequest:(NSURLRequest *)request {
NSString *url = request.URL.absoluteString;
NSString *fileName = [self cacheRequestFileName:url];
NSString *otherInfoFileName = [self cacheRequestOtherInfoFileName:url];
NSString *filePath = [self cacheFilePath:fileName];
NSString *otherInfoPath = [self cacheFilePath:otherInfoFileName];
NSDate *date = [NSDate date];
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:filePath]) {
BOOL expire = false;
NSDictionary *otherInfo = [NSDictionary dictionaryWithContentsOfFile:otherInfoPath];
float u=[date timeIntervalSince1970];
NSLog(@"%f",u);
if (self.cacheTime > 0) {
NSInteger createTime = [[otherInfo objectForKey:@"time"] intValue];
if (createTime + self.cacheTime < [date timeIntervalSince1970]) {
expire = true;
}
}
if (expire == false) {
NSLog(@"data from cache ...");
NSData *data = [NSData dataWithContentsOfFile:filePath];
NSURLResponse *response = [[NSURLResponse alloc] initWithURL:request.URL
MIMEType:[otherInfo objectForKey:@"MIMEType"]
expectedContentLength:data.length
textEncodingName:[otherInfo objectForKey:@"textEncodingName"]];
NSCachedURLResponse *cachedResponse = [[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];
[response release];
return cachedResponse;
} else {
NSLog(@"cache expire ... ");
[fileManager removeItemAtPath:filePath error:nil];
[fileManager removeItemAtPath:otherInfoPath error:nil];
}
}
//sendSynchronousRequest请求也要经过NSURLCache
id boolExsite = [self.responseDictionary objectForKey:url];
if (boolExsite == nil) {
[self.responseDictionary setValue:[NSNumber numberWithBool:TRUE] forKey:url];
NSError *error = nil;
NSURLResponse *response = nil;
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
[self.responseDictionary removeObjectForKey:url];
if (error) {
NSLog(@"error : %@", error);
NSLog(@"not cached: %@", request.URL.absoluteString);
return nil;
}
NSLog(@"get request ... ");
//save to cache
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"%f", [date timeIntervalSince1970]], @"time",
response.MIMEType, @"MIMEType",
response.textEncodingName, @"textEncodingName", nil];
[dict writeToFile:otherInfoPath atomically:YES];
[data writeToFile:filePath atomically:YES];
NSCachedURLResponse *cachedResponse = [[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];
return cachedResponse;
}
return nil;
}
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