該文章閱讀的AFNetworking的版本為3.2.0。
這個分類是為UIButton新增非同步載入網路圖片的方法
1.介面檔案
- 圖片下載器的訪問方法
/**
設定用於下載圖片的圖片下載器
*/
+ (void)setSharedImageDownloader:(AFImageDownloader *)imageDownloader;
/**
獲取用於下載圖片的圖片下載器
*/
+ (AFImageDownloader *)sharedImageDownloader;
複製程式碼- 為按鈕設定圖片的方法
/**
為按鈕設定指定狀態和指定圖片連結的圖片
*/
- (void)setImageForState:(UIControlState)state
withURL:(NSURL *)url;
/**
為按鈕設定指定狀態、指定圖片連結和指定佔點陣圖的圖片
*/
- (void)setImageForState:(UIControlState)state
withURL:(NSURL *)url
placeholderImage:(nullable UIImage *)placeholderImage;
/**
為按鈕設定指定狀態、指定圖片連結、指定佔點陣圖以及指定成功與失敗回撥block的圖片
*/
- (void)setImageForState:(UIControlState)state
withURLRequest:(NSURLRequest *)urlRequest
placeholderImage:(nullable UIImage *)placeholderImage
success:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, UIImage *image))success
failure:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, NSError *error))failure;
複製程式碼- 為按鈕設定背景圖片的方法
/**
為按鈕設定指定狀態和指定圖片連結的背景圖片
*/
- (void)setBackgroundImageForState:(UIControlState)state
withURL:(NSURL *)url;
/**
為按鈕設定指定狀態、指定圖片連結和指定佔點陣圖的背景圖片
*/
- (void)setBackgroundImageForState:(UIControlState)state
withURL:(NSURL *)url
placeholderImage:(nullable UIImage *)placeholderImage;
/**
為按鈕設定指定狀態、指定圖片連結、指定佔點陣圖以及指定成功與失敗回撥block的背景圖片
*/
- (void)setBackgroundImageForState:(UIControlState)state
withURLRequest:(NSURLRequest *)urlRequest
placeholderImage:(nullable UIImage *)placeholderImage
success:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, UIImage *image))success
failure:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, NSError *error))failure;
複製程式碼- 取消圖片載入方法
/**
取消按鈕在指定狀態下的所有圖片下載任務
*/
- (void)cancelImageDownloadTaskForState:(UIControlState)state;
/**
取消按鈕在指定狀態下的所有背景圖片下載任務
*/
- (void)cancelBackgroundImageDownloadTaskForState:(UIControlState)state;
複製程式碼2.實現檔案
2.1.UIButton+_AFNetworking私有分類
2.1.1.image相關
- 靜態字元
// 普通
static char AFImageDownloadReceiptNormal;
// 高亮
static char AFImageDownloadReceiptHighlighted;
// 已選
static char AFImageDownloadReceiptSelected;
// 禁用
static char AFImageDownloadReceiptDisabled;
複製程式碼- 靜態方法
/**
這個方法通過傳入的控制元件狀態返回對應的靜態字元
*/
static const char * af_imageDownloadReceiptKeyForState(UIControlState state) {
switch (state) {
case UIControlStateHighlighted:
return &AFImageDownloadReceiptHighlighted;
case UIControlStateSelected:
return &AFImageDownloadReceiptSelected;
case UIControlStateDisabled:
return &AFImageDownloadReceiptDisabled;
case UIControlStateNormal:
default:
return &AFImageDownloadReceiptNormal;
}
}
複製程式碼- 屬性的訪問方法
/**
通過Runtime的關聯物件為分類新增屬性的getter
*/
- (AFImageDownloadReceipt *)af_imageDownloadReceiptForState:(UIControlState)state {
return (AFImageDownloadReceipt *)objc_getAssociatedObject(self, af_imageDownloadReceiptKeyForState(state));
}
/**
通過Runtime的關聯物件為分類新增屬性的setter
*/
- (void)af_setImageDownloadReceipt:(AFImageDownloadReceipt *)imageDownloadReceipt
forState:(UIControlState)state
{
objc_setAssociatedObject(self, af_imageDownloadReceiptKeyForState(state), imageDownloadReceipt, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
複製程式碼2.1.2.backgroundImage相關
- 靜態字元
// 普通
static char AFBackgroundImageDownloadReceiptNormal;
// 高亮
static char AFBackgroundImageDownloadReceiptHighlighted;
// 已選
static char AFBackgroundImageDownloadReceiptSelected;
// 禁用
static char AFBackgroundImageDownloadReceiptDisabled;
複製程式碼- 靜態方法
/**
這個方法通過傳入的控制元件狀態返回對應的靜態字元
*/
static const char * af_backgroundImageDownloadReceiptKeyForState(UIControlState state) {
switch (state) {
case UIControlStateHighlighted:
return &AFBackgroundImageDownloadReceiptHighlighted;
case UIControlStateSelected:
return &AFBackgroundImageDownloadReceiptSelected;
case UIControlStateDisabled:
return &AFBackgroundImageDownloadReceiptDisabled;
case UIControlStateNormal:
default:
return &AFBackgroundImageDownloadReceiptNormal;
}
}
複製程式碼- 屬性的訪問方法
/**
通過Runtime的關聯物件為分類新增屬性的getter
*/
- (AFImageDownloadReceipt *)af_backgroundImageDownloadReceiptForState:(UIControlState)state {
return (AFImageDownloadReceipt *)objc_getAssociatedObject(self, af_backgroundImageDownloadReceiptKeyForState(state));
}
/**
通過Runtime的關聯物件為分類新增屬性的setter
*/
- (void)af_setBackgroundImageDownloadReceipt:(AFImageDownloadReceipt *)imageDownloadReceipt
forState:(UIControlState)state
{
objc_setAssociatedObject(self, af_backgroundImageDownloadReceiptKeyForState(state), imageDownloadReceipt, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
複製程式碼2.2.方法實現
- 屬性的訪問方法
/**
通過Runtime的關聯物件為分類新增sharedImageDownloader屬性的getter
*/
+ (AFImageDownloader *)sharedImageDownloader {
return objc_getAssociatedObject(self, @selector(sharedImageDownloader)) ?: [AFImageDownloader defaultInstance];
}
/**
通過Runtime的關聯物件為分類新增sharedImageDownloader屬性的setter
*/
+ (void)setSharedImageDownloader:(AFImageDownloader *)imageDownloader {
objc_setAssociatedObject(self, @selector(sharedImageDownloader), imageDownloader, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
複製程式碼- image相關介面方法實現
- (void)setImageForState:(UIControlState)state
withURL:(NSURL *)url
{
// 呼叫下面的方法
[self setImageForState:state withURL:url placeholderImage:nil];
}
- (void)setImageForState:(UIControlState)state
withURL:(NSURL *)url
placeholderImage:(UIImage *)placeholderImage
{
// 呼叫下面的方法
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request addValue:@"image/*" forHTTPHeaderField:@"Accept"];
[self setImageForState:state withURLRequest:request placeholderImage:placeholderImage success:nil failure:nil];
}
- (void)setImageForState:(UIControlState)state
withURLRequest:(NSURLRequest *)urlRequest
placeholderImage:(nullable UIImage *)placeholderImage
success:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, UIImage *image))success
failure:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, NSError *error))failure
{
// 如果這個網路請求正在進行中就不重複執行了
if ([self isActiveTaskURLEqualToURLRequest:urlRequest forState:state]) {
return;
}
// 取消掉這個狀態的圖片下載任務
[self cancelImageDownloadTaskForState:state];
// 例項化圖片下載器
AFImageDownloader *downloader = [[self class] sharedImageDownloader];
// 獲取到圖片快取物件
id <AFImageRequestCache> imageCache = downloader.imageCache;
// 獲取到快取圖片
UIImage *cachedImage = [imageCache imageforRequest:urlRequest withAdditionalIdentifier:nil];
// 如果有快取
if (cachedImage) {
// 如果設定了成功回撥block就呼叫，否則就為按鈕設定圖片
if (success) {
success(urlRequest, nil, cachedImage);
} else {
[self setImage:cachedImage forState:state];
}
[self af_setImageDownloadReceipt:nil forState:state];
// 如果沒有快取
} else {
// 如果有佔點陣圖先設定佔點陣圖
if (placeholderImage) {
[self setImage:placeholderImage forState:state];
}
// 開始下載
__weak __typeof(self)weakSelf = self;
NSUUID *downloadID = [NSUUID UUID];
AFImageDownloadReceipt *receipt;
receipt = [downloader
downloadImageForURLRequest:urlRequest
withReceiptID:downloadID
success:^(NSURLRequest * _Nonnull request, NSHTTPURLResponse * _Nullable response, UIImage * _Nonnull responseObject) {
// 如果是當前按鈕的下載回撥
__strong __typeof(weakSelf)strongSelf = weakSelf;
if ([[strongSelf af_imageDownloadReceiptForState:state].receiptID isEqual:downloadID]) {
// 如果設定了成功回撥block就呼叫，否則就為按鈕設定圖片
if (success) {
success(request, response, responseObject);
} else if(responseObject) {
[strongSelf setImage:responseObject forState:state];
}
// 將儲存下載封裝物件的屬性置nil
[strongSelf af_setImageDownloadReceipt:nil forState:state];
}
}
failure:^(NSURLRequest * _Nonnull request, NSHTTPURLResponse * _Nullable response, NSError * _Nonnull error) {
// 如果是當前按鈕的下載回撥
__strong __typeof(weakSelf)strongSelf = weakSelf;
if ([[strongSelf af_imageDownloadReceiptForState:state].receiptID isEqual:downloadID]) {
// 失敗回撥block
if (failure) {
failure(request, response, error);
}
// 將儲存下載封裝物件的屬性置nil
[strongSelf af_setImageDownloadReceipt:nil forState:state];
}
}];
// 用分類的屬性儲存圖片下載封裝物件
[self af_setImageDownloadReceipt:receipt forState:state];
}
}
- (void)cancelImageDownloadTaskForState:(UIControlState)state {
// 通過狀態獲取到圖片下載封裝物件
AFImageDownloadReceipt *receipt = [self af_imageDownloadReceiptForState:state];
if (receipt != nil) {
// 根據獲取到的圖片下載封裝物件取消對應的圖片下載任務
[[self.class sharedImageDownloader] cancelTaskForImageDownloadReceipt:receipt];
// 把儲存圖片下載封裝物件的屬性置nil
[self af_setImageDownloadReceipt:nil forState:state];
}
}
複製程式碼- backgroundImage相關介面方法實現
backgroundImage的實現和image的實現除了在設定圖片時一個給backgroundImage，一個給image之外都相同。
- (void)setBackgroundImageForState:(UIControlState)state
withURL:(NSURL *)url
{
[self setBackgroundImageForState:state withURL:url placeholderImage:nil];
}
- (void)setBackgroundImageForState:(UIControlState)state
withURL:(NSURL *)url
placeholderImage:(nullable UIImage *)placeholderImage
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request addValue:@"image/*" forHTTPHeaderField:@"Accept"];
[self setBackgroundImageForState:state withURLRequest:request placeholderImage:placeholderImage success:nil failure:nil];
}
- (void)setBackgroundImageForState:(UIControlState)state
withURLRequest:(NSURLRequest *)urlRequest
placeholderImage:(nullable UIImage *)placeholderImage
success:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, UIImage *image))success
failure:(nullable void (^)(NSURLRequest *request, NSHTTPURLResponse * _Nullable response, NSError *error))failure
{
if ([self isActiveBackgroundTaskURLEqualToURLRequest:urlRequest forState:state]) {
return;
}
[self cancelBackgroundImageDownloadTaskForState:state];
AFImageDownloader *downloader = [[self class] sharedImageDownloader];
id <AFImageRequestCache> imageCache = downloader.imageCache;
//Use the image from the image cache if it exists
UIImage *cachedImage = [imageCache imageforRequest:urlRequest withAdditionalIdentifier:nil];
if (cachedImage) {
if (success) {
success(urlRequest, nil, cachedImage);
} else {
[self setBackgroundImage:cachedImage forState:state];
}
[self af_setBackgroundImageDownloadReceipt:nil forState:state];
} else {
if (placeholderImage) {
[self setBackgroundImage:placeholderImage forState:state];
}
__weak __typeof(self)weakSelf = self;
NSUUID *downloadID = [NSUUID UUID];
AFImageDownloadReceipt *receipt;
receipt = [downloader
downloadImageForURLRequest:urlRequest
withReceiptID:downloadID
success:^(NSURLRequest * _Nonnull request, NSHTTPURLResponse * _Nullable response, UIImage * _Nonnull responseObject) {
__strong __typeof(weakSelf)strongSelf = weakSelf;
if ([[strongSelf af_backgroundImageDownloadReceiptForState:state].receiptID isEqual:downloadID]) {
if (success) {
success(request, response, responseObject);
} else if(responseObject) {
[strongSelf setBackgroundImage:responseObject forState:state];
}
[strongSelf af_setBackgroundImageDownloadReceipt:nil forState:state];
}
}
failure:^(NSURLRequest * _Nonnull request, NSHTTPURLResponse * _Nullable response, NSError * _Nonnull error) {
__strong __typeof(weakSelf)strongSelf = weakSelf;
if ([[strongSelf af_backgroundImageDownloadReceiptForState:state].receiptID isEqual:downloadID]) {
if (failure) {
failure(request, response, error);
}
[strongSelf af_setBackgroundImageDownloadReceipt:nil forState:state];
}
}];
[self af_setBackgroundImageDownloadReceipt:receipt forState:state];
}
}
- (void)cancelBackgroundImageDownloadTaskForState:(UIControlState)state {
AFImageDownloadReceipt *receipt = [self af_backgroundImageDownloadReceiptForState:state];
if (receipt != nil) {
[[self.class sharedImageDownloader] cancelTaskForImageDownloadReceipt:receipt];
[self af_setBackgroundImageDownloadReceipt:nil forState:state];
}
}
複製程式碼- 私有方法
/**
判斷圖片下載請求是否已經正在進行中
*/
- (BOOL)isActiveTaskURLEqualToURLRequest:(NSURLRequest *)urlRequest forState:(UIControlState)state {
// 先根據狀態獲取到屬性中儲存的圖片下載封裝物件
AFImageDownloadReceipt *receipt = [self af_imageDownloadReceiptForState:state];
// 根據兩者的連結是否相同進行比較
return [receipt.task.originalRequest.URL.absoluteString isEqualToString:urlRequest.URL.absoluteString];
}
/**
判斷背景圖片下載請求是否已經正在進行中
*/
- (BOOL)isActiveBackgroundTaskURLEqualToURLRequest:(NSURLRequest *)urlRequest forState:(UIControlState)state {
// 實現和上面的方法相同
AFImageDownloadReceipt *receipt = [self af_backgroundImageDownloadReceiptForState:state];
return [receipt.task.originalRequest.URL.absoluteString isEqualToString:urlRequest.URL.absoluteString];
}
複製程式碼3.總結
當我們利用這個分類為按鈕設定圖片時
- 首先會根據要設定的控制元件狀態和圖片連結判斷是否是重複下載，如果是重複下載就不繼續向下進行了。
- 接著會取消在設定的控制元件狀態下正在進行的下載操作（如果有的話），也就是說只有最新的這次圖片設定才有效。
- 然後獲取到圖片下載器的圖片快取物件，從圖片快取物件中查詢是否有快取，如果有快取的話會直接取出新增到按鈕上，但是如果使用者設定了成功回撥block，就不會將圖片新增到按鈕上，而是會呼叫blokc，將結果傳遞給使用者，讓使用者來處理。
- 如果沒有快取，就會先判斷有沒有佔點陣圖，如果有佔點陣圖的話，就先給按鈕設定佔點陣圖。
- 接下來將UUID作為識別符號開啟圖片下載任務，並將任務封裝物件儲存在屬性中，屬性的命名是根據圖片要設定的控制元件狀態相關聯的。
- 下載任務執行完成後，無論成功還是失敗，都會先根據設定的控制元件狀態獲取到對應的下載任務封裝物件，對比下載任務封裝物件的識別符號和UUID判斷是否是同一任務的回撥，只用是同一任務的回撥才繼續執行
- 在下載成功的情況下，如果使用者設定了成功回撥block，就呼叫block，將結果傳遞給使用者，讓使用者來處理，如果沒有設定，就直接將下載好的圖片新增到按鈕的指定狀態上，並將指定狀態所對應的儲存下載任務封裝物件的屬性置nil。
- 當下載失敗時，如果使用者設定了失敗回撥block，就呼叫block，將結果傳遞給使用者，讓使用者來處理，如果沒有設定，就將指定狀態所對應的儲存下載任務封裝物件的屬性置nil。
原始碼閱讀系列：AFNetworking
原始碼閱讀：AFNetworking（二）——AFURLRequestSerialization
原始碼閱讀：AFNetworking（三）——AFURLResponseSerialization
原始碼閱讀：AFNetworking（四）——AFSecurityPolicy
原始碼閱讀：AFNetworking（五）——AFNetworkReachabilityManager
原始碼閱讀：AFNetworking（六）——AFURLSessionManager
原始碼閱讀：AFNetworking（七）——AFHTTPSessionManager
原始碼閱讀：AFNetworking（八）——AFAutoPurgingImageCache
原始碼閱讀：AFNetworking（九）——AFImageDownloader
原始碼閱讀：AFNetworking（十）——AFNetworkActivityIndicatorManager
原始碼閱讀：AFNetworking（十一）——UIActivityIndicatorView+AFNetworking
原始碼閱讀：AFNetworking（十二）——UIButton+AFNetworking
原始碼閱讀：AFNetworking（十三）——UIImageView+AFNetworking
原始碼閱讀：AFNetworking（十四）——UIProgressView+AFNetworking