AFNetworking2.0源码解析<四>
2014-11-18
续AFNetworking2.0源码解析<一><二><三>，本篇来看看AFURLResponseSerialization做的事情。
结构
AFURLResponseSerialization负责解析网络返回数据，检查数据是否合法，把NSData数据转成相应的对象，内置的转换器有json,xml,plist,image，用户可以很方便地继承基类AFHTTPResponseSerializer去解析更多的数据格式，AFNetworking这一套响应解析机制结构很简单，主要就是两个方法：
1.-validateResponse:data:error:
基类AFHTTPResponseSerializer的这个方法检测返回的HTTP状态码和数据类型是否合法，属性acceptableStatusCodes和acceptableContentTypes规定了合法的状态码和数据类型，例如JSONSerialization就把acceptableContentTypes设为@”application/json”, @”text/json”, @”text/javascript”，若不是这三者之一，就验证失败，返回相应的NSError对象。一般子类不需要重写这个方法，只需要设置好acceptableStatusCodes和acceptableContentTypes就行了。
2.-responseObjectForResponse:data:error:
这个方法解析数据，把NSData转成相应的对象，上层AFURLConnectionOperation会调用这个方法获取转换后的对象。
在解析数据之前会先调上述的validateResponse方法检测HTTP响应是否合法，要注意的是即使这里检测返回不合法，也会继续解析数据生成对象，因为有可能错误信息就在返回的数据里。
如果validateResponse返回error，这里的解析数据又出错，这时有两个error对象，怎样返回给上层？这里的处理是把解析数据的NSError对象保存到validateResponse NSError的userInfo里，作为UnderlyingError，NSError专门给了个NSUnderlyingErrorKey作为这种错误包含错误的键值。
剩下的就是NSecureCoding相关方法了，如果子类增加了property，需要加上相应的NSecureCoding方法。
JSON解析
AFJSONResponseSerializer使用系统内置的NSJSONSerialization解析json，NSJSON只支持解析UTF8编码的数据（还有UTF-16LE之类的，都不常用），所以要先把返回的数据转成UTF8格式。这里会尝试用HTTP返回的编码类型和自己设置的stringEncoding去把数据解码转成字符串NSString，再把NSString用UTF8编码转成NSData，再用NSJSONSerialization解析成对象返回。
上述过程是NSData->NSString->NSData->NSObject，这里有个问题，如果你能确定服务端返回的是UTF8编码的json数据，那NSData->NSString->NSData这两步就是无意义的，而且这两步进行了两次编解码，很浪费性能，所以如果确定服务端返回utf8编码数据，就建议自己再写个JSONResponseSerializer，跳过这两个步骤。
此外AFJSONResponseSerializer专门写了个方法去除NSNull，直接把对象里值是NSNull的键去掉，还蛮贴心，若不去掉，上层很容易忽略了这个数据类型，判断了数据是否nil没判断是否NSNull，进行了错误的调用导致core。
图片解压
当我们调用UIImage的方法imageWithData:方法把数据转成UIImage对象后，其实这时UIImage对象还没准备好需要渲染到屏幕的数据，现在的网络图像PNG和JPG都是压缩格式，需要把它们解压转成bitmap后才能渲染到屏幕上，如果不做任何处理，当你把UIImage赋给UIImageView，在渲染之前底层会判断到UIImage对象未解压，没有bitmap数据，这时会在主线程对图片进行解压操作，再渲染到屏幕上。这个解压操作是比较耗时的，如果任由它在主线程做，可能会导致速度慢UI卡顿的问题。
AFImageResponseSerializer除了把返回数据解析成UIImage外，还会把图像数据解压，这个处理是在子线程（AFNetworking专用的一条线程，详见AFURLConnectionOperation），处理后上层使用返回的UIImage在主线程渲染时就不需要做解压这步操作，主线程减轻了负担，减少了UI卡顿问题。
具体实现上在AFInflatedImageFromResponseWithDataAtScale里，创建一个画布，把UIImage画在画布上，再把这个画布保存成UIImage返回给上层。只有JPG和PNG才会尝试去做解压操作，期间如果解压失败，或者遇到CMKY颜色格式的jpg，或者图像太大(解压后的bitmap太占内存，一个像素3-4字节，搞不好内存就爆掉了)，就直接返回未解压的图像。
另外在代码里看到iOS才需要这样手动解压，MacOS上已经有封装好的对象NSBitmapImageRep可以做这个事。
关于图片解压，还有几个问题不清楚：
1.本来以为调用imageWithData方法只是持有了数据，没有做解压相关的事，后来看到调用堆栈发现已经做了一些解压操作，从调用名字看进行了huffman解码，不知还会继续做到解码jpg的哪一步。
2.以上图片手动解压方式都是在CPU进行的，如果不进行手动解压，把图片放进layer里，让底层自动做这个事，是会用GPU进行的解压的。不知用GPU解压与用CPU解压速度会差多少，如果GPU速度很快，就算是在主线程做解压，也变得可以接受了，就不需要手动解压这样的优化了，不过目前没找到方法检测GPU解压的速度。
P.S. 关于图片解压，有篇挺挺不错的文章：Avoiding Image Decompression Sickness
源码注释
// AFSerialization.h
//
// Copyright (c) 2013-2014 AFNetworking (http://afnetworking.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#import "AFURLResponseSerialization.h"
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
#import <UIKit/UIKit.h>
#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
#import <Cocoa/Cocoa.h>
#endif
NSString * const AFURLResponseSerializationErrorDomain = @"com.alamofire.error.serialization.response";
NSString * const AFNetworkingOperationFailingURLResponseErrorKey = @"com.alamofire.serialization.response.error.response";
//把一个NSError对象作为另一个NSError的附属Error，放在userInfo的NSUnderlyingErrorKey键里
static NSError * AFErrorWithUnderlyingError(NSError *error, NSError *underlyingError) {
if (!error) {
return underlyingError;
}
if (!underlyingError || error.userInfo[NSUnderlyingErrorKey]) {
return error;
}
NSMutableDictionary *mutableUserInfo = [error.userInfo mutableCopy];
mutableUserInfo[NSUnderlyingErrorKey] = underlyingError;
return [[NSError alloc] initWithDomain:error.domain code:error.code userInfo:mutableUserInfo];
}
//NSError对象是否指定domain和code，把UnderlyingError也给判断了
static BOOL AFErrorOrUnderlyingErrorHasCodeInDomain(NSError *error, NSInteger code, NSString *domain) {
if ([error.domain isEqualToString:domain] && error.code == code) {
return YES;
} else if (error.userInfo[NSUnderlyingErrorKey]) {
return AFErrorOrUnderlyingErrorHasCodeInDomain(error.userInfo[NSUnderlyingErrorKey], code, domain);
}
return NO;
}
//删除JSON NSDictionary数据里的NSNull对象，直接去掉这个键
static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingOptions readingOptions) {
if ([JSONObject isKindOfClass:[NSArray class]]) {
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:[(NSArray *)JSONObject count]];
for (id value in (NSArray *)JSONObject) {
[mutableArray addObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions)];
}
return (readingOptions & NSJSONReadingMutableContainers) ? mutableArray : [NSArray arrayWithArray:mutableArray];
} else if ([JSONObject isKindOfClass:[NSDictionary class]]) {
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:JSONObject];
for (id <NSCopying> key in [(NSDictionary *)JSONObject allKeys]) {
id value = [(NSDictionary *)JSONObject objectForKey:key];
if (!value || [value isEqual:[NSNull null]]) {
[mutableDictionary removeObjectForKey:key];
} else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]]) {
[mutableDictionary setObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions) forKey:key];
}
}
return (readingOptions & NSJSONReadingMutableContainers) ? mutableDictionary : [NSDictionary dictionaryWithDictionary:mutableDictionary];
}
return JSONObject;
}
@implementation AFHTTPResponseSerializer
+ (instancetype)serializer {
return [[self alloc] init];
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
//默认UTF8编码，若HTTP Response里没有encoding数据，会用这个编码去解码数据
self.stringEncoding = NSUTF8StringEncoding;
//只接受HTTP状态码2xx，2xx在HTTP状态码里表示请求成功
self.acceptableStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(200, 100)];
//默认任何数据类型都接受
self.acceptableContentTypes = nil;
return self;
}
#pragma mark -
- (BOOL)validateResponse:(NSHTTPURLResponse *)response
data:(NSData *)data
error:(NSError * __autoreleasing *)error
{
BOOL responseIsValid = YES;
NSError *validationError = nil;
if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]]) {
//返回的数据类型不在定义的acceptableContentTypes里，不合法
if ([data length] > 0) {
//如果有数据，给出一个 不能解码 的NSError
//responseObjectForResponse里若判断到是这个Error，就不解析数据了
NSDictionary *userInfo = @{
NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
NSURLErrorFailingURLErrorKey:[response URL],
AFNetworkingOperationFailingURLResponseErrorKey: response
};
validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo], validationError);
}
//如果连数据都没有，就没数据类型什么事了，不算error
responseIsValid = NO;
}
if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode]) {
//返回的HTTP状态码不在可接受范围内
NSDictionary *userInfo = @{
NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
NSURLErrorFailingURLErrorKey:[response URL],
AFNetworkingOperationFailingURLResponseErrorKey: response
};
validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:userInfo], validationError);
responseIsValid = NO;
}
}
if (error && !responseIsValid) {
*error = validationError;
}
return responseIsValid;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
[self validateResponse:(NSHTTPURLResponse *)response data:data error:error];
return data;
}
#pragma mark - NSecureCoding
//用于对象序列化保存和反序列化取出的NSecureCoding方法们，以及用于copy的copyWithZone方法
//子类若有新增属性，需要一个个写上
+ (BOOL)supportsSecureCoding {
return YES;
}
- (id)initWithCoder:(NSCoder *)decoder {
self = [self init];
if (!self) {
return nil;
}
self.acceptableStatusCodes = [decoder decodeObjectOfClass:[NSIndexSet class] forKey:NSStringFromSelector(@selector(acceptableStatusCodes))];
self.acceptableContentTypes = [decoder decodeObjectOfClass:[NSIndexSet class] forKey:NSStringFromSelector(@selector(acceptableContentTypes))];
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[coder encodeObject:self.acceptableStatusCodes forKey:NSStringFromSelector(@selector(acceptableStatusCodes))];
[coder encodeObject:self.acceptableContentTypes forKey:NSStringFromSelector(@selector(acceptableContentTypes))];
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFHTTPResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
serializer.acceptableStatusCodes = [self.acceptableStatusCodes copyWithZone:zone];
serializer.acceptableContentTypes = [self.acceptableContentTypes copyWithZone:zone];
return serializer;
}
@end
#pragma mark -
@implementation AFJSONResponseSerializer
+ (instancetype)serializer {
return [self serializerWithReadingOptions:0];
}
+ (instancetype)serializerWithReadingOptions:(NSJSONReadingOptions)readingOptions {
AFJSONResponseSerializer *serializer = [[self alloc] init];
serializer.readingOptions = readingOptions;
return serializer;
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.acceptableContentTypes = [NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript", nil];
return self;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
//先调基类的方法验证response是否有错误，
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
//若验证不通过，但又没有错误信息，不知道是什么错误，直接返回
//若是数据类型错误，不进行数据的解析，直接返回，否则要解析数据，因为数据里可能有错误信息。
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
// Workaround for behavior of Rails to return a single space for `head :ok` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization.
// See https://github.com/rails/rails/issues/1742
NSStringEncoding stringEncoding = self.stringEncoding;
if (response.textEncodingName) {
//优先尝试用HTTP返回的编码类型，没有或不合法才用属性self.stringEncoding的编码类型
CFStringEncoding encoding = CFStringConvertIANACharSetNameToEncoding((CFStringRef)response.textEncodingName);
if (encoding != kCFStringEncodingInvalidId) {
stringEncoding = CFStringConvertEncodingToNSStringEncoding(encoding);
}
}
id responseObject = nil;
NSError *serializationError = nil;
@autoreleasepool {
//json数据可能比较大，这里responseString分别持有了拷贝，要让它尽快释放，所以加了@autoreleasepool，不用等到整个循环执行完到下个runloop才释放这个大对象
//**先用指定编码类型解码
NSString *responseString = [[NSString alloc] initWithData:data encoding:stringEncoding];
if (responseString && ![responseString isEqualToString:@" "]) {
// Workaround for a bug in NSJSONSerialization when Unicode character escape codes are used instead of the actual character
// See http://stackoverflow.com/a/12843465/157142
//**再用UTF8编码
data = [responseString dataUsingEncoding:NSUTF8StringEncoding];
if (data) {
//data不为nil就是解析成功，若解析成功后字符串长度为0，就不算解析失败，直接返回object为nil
if ([data length] > 0) {
//**最后转成NSArray/NSDictiony对象
responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];
} else {
return nil;
}
} else {
//解析失败，构建NSError返回
NSDictionary *userInfo = @{
NSLocalizedDescriptionKey: NSLocalizedStringFromTable(@"Data failed decoding as a UTF-8 string", nil, @"AFNetworking"),
NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Could not decode string: %@", nil, @"AFNetworking"), responseString]
};
serializationError = [NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo];
}
}
}
if (self.removesKeysWithNullValues && responseObject) {
//清除所有NSNull对象
responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
}
if (error) {
//如果validateResponse已返回error，把序列化的error对象加到valid的error对象里，作为underlyingError
*error = AFErrorWithUnderlyingError(serializationError, *error);;
}
return responseObject;
}
#pragma mark - NSecureCoding
- (id)initWithCoder:(NSCoder *)decoder {
self = [super initWithCoder:decoder];
if (!self) {
return nil;
}
self.readingOptions = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(readingOptions))] unsignedIntegerValue];
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:@(self.readingOptions) forKey:NSStringFromSelector(@selector(readingOptions))];
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFJSONResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
serializer.readingOptions = self.readingOptions;
return serializer;
}
@end
#pragma mark -
@implementation AFXMLParserResponseSerializer
+ (instancetype)serializer {
AFXMLParserResponseSerializer *serializer = [[self alloc] init];
return serializer;
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/xml", @"text/xml", nil];
return self;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSHTTPURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
return [[NSXMLParser alloc] initWithData:data];
}
@end
#pragma mark -
#ifdef __MAC_OS_X_VERSION_MIN_REQUIRED
@implementation AFXMLDocumentResponseSerializer
+ (instancetype)serializer {
return [self serializerWithXMLDocumentOptions:0];
}
+ (instancetype)serializerWithXMLDocumentOptions:(NSUInteger)mask {
AFXMLDocumentResponseSerializer *serializer = [[self alloc] init];
serializer.options = mask;
return serializer;
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/xml", @"text/xml", nil];
return self;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
NSError *serializationError = nil;
NSXMLDocument *document = [[NSXMLDocument alloc] initWithData:data options:self.options error:&serializationError];
if (error) {
*error = AFErrorWithUnderlyingError(serializationError, *error);
}
return document;
}
#pragma mark - NSecureCoding
- (id)initWithCoder:(NSCoder *)decoder {
self = [super initWithCoder:decoder];
if (!self) {
return nil;
}
self.options = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(options))] unsignedIntegerValue];
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:@(self.options) forKey:NSStringFromSelector(@selector(options))];
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFXMLDocumentResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
serializer.options = self.options;
return serializer;
}
@end
#endif
#pragma mark -
@implementation AFPropertyListResponseSerializer
+ (instancetype)serializer {
return [self serializerWithFormat:NSPropertyListXMLFormat_v1_0 readOptions:0];
}
+ (instancetype)serializerWithFormat:(NSPropertyListFormat)format
readOptions:(NSPropertyListReadOptions)readOptions
{
AFPropertyListResponseSerializer *serializer = [[self alloc] init];
serializer.format = format;
serializer.readOptions = readOptions;
return serializer;
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/x-plist", nil];
return self;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
id responseObject;
NSError *serializationError = nil;
if (data) {
responseObject = [NSPropertyListSerialization propertyListWithData:data options:self.readOptions format:NULL error:&serializationError];
}
if (error) {
*error = AFErrorWithUnderlyingError(serializationError, *error);
}
return responseObject;
}
#pragma mark - NSecureCoding
- (id)initWithCoder:(NSCoder *)decoder {
self = [super initWithCoder:decoder];
if (!self) {
return nil;
}
self.format = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(format))] unsignedIntegerValue];
self.readOptions = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(readOptions))] unsignedIntegerValue];
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:@(self.format) forKey:NSStringFromSelector(@selector(format))];
[coder encodeObject:@(self.readOptions) forKey:NSStringFromSelector(@selector(readOptions))];
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFPropertyListResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
serializer.format = self.format;
serializer.readOptions = self.readOptions;
return serializer;
}
@end
#pragma mark -
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
#import <CoreGraphics/CoreGraphics.h>
static UIImage * AFImageWithDataAtScale(NSData *data, CGFloat scale) {
//不清楚这里为什么不用[[UIImage alloc] initWithData:data scale:scale]而要创建两次UIImage
UIImage *image = [[UIImage alloc] initWithData:data];
return [[UIImage alloc] initWithCGImage:[image CGImage] scale:scale orientation:image.imageOrientation];
}
static UIImage * AFInflatedImageFromResponseWithDataAtScale(NSHTTPURLResponse *response, NSData *data, CGFloat scale) {
if (!data || [data length] == 0) {
return nil;
}
CGImageRef imageRef = NULL;
CGDataProviderRef dataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
if ([response.MIMEType isEqualToString:@"image/png"]) {
imageRef = CGImageCreateWithPNGDataProvider(dataProvider, NULL, true, kCGRenderingIntentDefault);
} else if ([response.MIMEType isEqualToString:@"image/jpeg"]) {
imageRef = CGImageCreateWithJPEGDataProvider(dataProvider, NULL, true, kCGRenderingIntentDefault);
// CGImageCreateWithJPEGDataProvider does not properly handle CMKY, so if so, fall back to AFImageWithDataAtScale
//英文解释得挺清楚了，如果jpg的色彩空间是CMKY而不是RGB的话，不进行解压
if (imageRef) {
CGColorSpaceRef imageColorSpace = CGImageGetColorSpace(imageRef);
CGColorSpaceModel imageColorSpaceModel = CGColorSpaceGetModel(imageColorSpace);
if (imageColorSpaceModel == kCGColorSpaceModelCMYK) {
CGImageRelease(imageRef);
imageRef = NULL;
}
}
}
CGDataProviderRelease(dataProvider);
//这里创建了UIImage对象，用于不符合解压条件时直接返回未解压的UIImage
//这里这样创建代码写起来是方便了，但无论符不符合解压条件，这个备用的UIImage都生成了，浪费了性能
UIImage *image = AFImageWithDataAtScale(data, scale);
if (!imageRef) {
//images是用于做动画的多张图片，如果是这个类型，或者image对象生成失败，直接返回
if (image.images || !image) {
return image;
}
//TODO 为毛要copy呢
imageRef = CGImageCreateCopy([image CGImage]);
if (!imageRef) {
return nil;
}
}
//获取图片宽高和存储一个像素需要用到的字节数
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);
//图片太大了就不解压了，因为解压后bitmap数据一直保存在UIImage对象里，有可能把内存撑爆了
//如果一个像素的字节数大于8也不解压，一般RGBA每个颜色2byte，一共8byte，不清楚什么情况下会有大于8字节的
if (width * height > 1024 * 1024 || bitsPerComponent > 8) {
CGImageRelease(imageRef);
return image;
}
//画布的参数
size_t bytesPerRow = 0; // CGImageGetBytesPerRow() calculates incorrectly in iOS 5.0, so defer to CGBitmapContextCreate
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGColorSpaceModel colorSpaceModel = CGColorSpaceGetModel(colorSpace);
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
if (colorSpaceModel == kCGColorSpaceModelRGB) {
uint32_t alpha = (bitmapInfo & kCGBitmapAlphaInfoMask);
if (alpha == kCGImageAlphaNone) {
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
bitmapInfo |= kCGImageAlphaNoneSkipFirst;
} else if (!(alpha == kCGImageAlphaNoneSkipFirst || alpha == kCGImageAlphaNoneSkipLast)) {
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
bitmapInfo |= kCGImageAlphaPremultipliedFirst;
}
}
//生成像素画布
CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);
CGColorSpaceRelease(colorSpace);
if (!context) {
CGImageRelease(imageRef);
return image;
}
//在画布上画出图片，保存成CGImageRef对象，转成UIImage，完成解压
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), imageRef);
CGImageRef inflatedImageRef = CGBitmapContextCreateImage(context);
CGContextRelease(context);
UIImage *inflatedImage = [[UIImage alloc] initWithCGImage:inflatedImageRef scale:scale orientation:image.imageOrientation];
CGImageRelease(inflatedImageRef);
CGImageRelease(imageRef);
return inflatedImage;
}
#endif
@implementation AFImageResponseSerializer
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"image/tiff", @"image/jpeg", @"image/gif", @"image/png", @"image/ico", @"image/x-icon", @"image/bmp", @"image/x-bmp", @"image/x-xbitmap", @"image/x-win-bitmap", nil];
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
self.imageScale = [[UIScreen mainScreen] scale];
self.automaticallyInflatesResponseImage = YES;
#endif
return self;
}
#pragma mark - AFURLResponseSerializer
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
//iOS需要手动解压
if (self.automaticallyInflatesResponseImage) {
return AFInflatedImageFromResponseWithDataAtScale((NSHTTPURLResponse *)response, data, self.imageScale);
} else {
return AFImageWithDataAtScale(data, self.imageScale);
}
#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
//MacOS直接有内置方法可以解压
// Ensure that the image is set to it's correct pixel width and height
NSBitmapImageRep *bitimage = [[NSBitmapImageRep alloc] initWithData:data];
NSImage *image = [[NSImage alloc] initWithSize:NSMakeSize([bitimage pixelsWide], [bitimage pixelsHigh])];
[image addRepresentation:bitimage];
return image;
#endif
return nil;
}
#pragma mark - NSecureCoding
- (id)initWithCoder:(NSCoder *)decoder {
self = [super initWithCoder:decoder];
if (!self) {
return nil;
}
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
NSNumber *imageScale = [decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(imageScale))];
#if CGFLOAT_IS_DOUBLE
self.imageScale = [imageScale doubleValue];
#else
self.imageScale = [imageScale floatValue];
#endif
self.automaticallyInflatesResponseImage = [decoder decodeBoolForKey:NSStringFromSelector(@selector(automaticallyInflatesResponseImage))];
#endif
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
[coder encodeObject:@(self.imageScale) forKey:NSStringFromSelector(@selector(imageScale))];
[coder encodeBool:self.automaticallyInflatesResponseImage forKey:NSStringFromSelector(@selector(automaticallyInflatesResponseImage))];
#endif
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFImageResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)
serializer.imageScale = self.imageScale;
serializer.automaticallyInflatesResponseImage = self.automaticallyInflatesResponseImage;
#endif
return serializer;
}
@end
#pragma mark -
//可以自动尝试用多个ResponseSerializer解析数据的Serializer
@interface AFCompoundResponseSerializer ()
@property (readwrite, nonatomic, copy) NSArray *responseSerializers;
@end
@implementation AFCompoundResponseSerializer
+ (instancetype)compoundSerializerWithResponseSerializers:(NSArray *)responseSerializers {
AFCompoundResponseSerializer *serializer = [[self alloc] init];
serializer.responseSerializers = responseSerializers;
return serializer;
}
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
//遍历所有ResponseSerializater，能解析出来就返回，解析不了就尝试下一个
for (id <AFURLResponseSerialization> serializer in self.responseSerializers) {
if (![serializer isKindOfClass:[AFHTTPResponseSerializer class]]) {
continue;
}
NSError *serializerError = nil;
id responseObject = [serializer responseObjectForResponse:response data:data error:&serializerError];
if (responseObject) {
if (error) {
*error = AFErrorWithUnderlyingError(serializerError, *error);
}
return responseObject;
}
}
return [super responseObjectForResponse:response data:data error:error];
}
#pragma mark - NSecureCoding
- (id)initWithCoder:(NSCoder *)decoder {
self = [super initWithCoder:decoder];
if (!self) {
return nil;
}
self.responseSerializers = [decoder decodeObjectOfClass:[NSArray class] forKey:NSStringFromSelector(@selector(responseSerializers))];
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[super encodeWithCoder:coder];
[coder encodeObject:self.responseSerializers forKey:NSStringFromSelector(@selector(responseSerializers))];
}
#pragma mark - NSCopying
- (id)copyWithZone:(NSZone *)zone {
AFCompoundResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];
serializer.responseSerializers = self.responseSerializers;
return serializer;
}
@end
你好bang，我也叫bang，没想到撞上了同样的名字，我很惊讶，这是我的qq：1805475204
你想到bang这个名字是为什么呢？
希望我们可以交上朋友