SDWebImage源码解读（四）UIButton+WebCache

时间：2017-08-30 19:53:10 阅读：255 评论：0 收藏：0 [点我收藏+]

UIButton+WebCache

.h 文件

1.获取当前button的图片url。

- (nullable NSURL *)sd_currentImageURL;

2.根据不同的状态获取图片url。

- (nullable NSURL *)sd_imageURLForState:(UIControlState)state;

3.设置按钮不同状态的url，然后异步加载，并且缓存。

 1 - (void)sd_setImageWithURL:(nullable NSURL *)url
 2                   forState:(UIControlState)state;
 3 
 4 - (void)sd_setImageWithURL:(nullable NSURL *)url
 5                   forState:(UIControlState)state
 6           placeholderImage:(nullable UIImage *)placeholder;
 7 
 8 - (void)sd_setImageWithURL:(nullable NSURL *)url
 9                   forState:(UIControlState)state
10           placeholderImage:(nullable UIImage *)placeholder
11                    options:(SDWebImageOptions)options;
12 
13 - (void)sd_setImageWithURL:(nullable NSURL *)url
14                   forState:(UIControlState)state
15                  completed:(nullable SDExternalCompletionBlock)completedBlock;
16 
17 - (void)sd_setImageWithURL:(nullable NSURL *)url
18                   forState:(UIControlState)state
19           placeholderImage:(nullable UIImage *)placeholder
20                  completed:(nullable SDExternalCompletionBlock)completedBlock;

这几个方法的实现全部调用这个方法实现：

1 - (void)sd_setImageWithURL:(nullable NSURL *)url
2                   forState:(UIControlState)state
3           placeholderImage:(nullable UIImage *)placeholder
4                    options:(SDWebImageOptions)options
5                  completed:(nullable SDExternalCompletionBlock)completedBlock;

4.我们再来看这几个方法：

 1 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
 2                             forState:(UIControlState)state;
 3 
 4 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
 5                             forState:(UIControlState)state
 6                     placeholderImage:(nullable UIImage *)placeholder;
 7 
 8 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
 9                             forState:(UIControlState)state
10                     placeholderImage:(nullable UIImage *)placeholder
11                              options:(SDWebImageOptions)options;
12 
13 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
14                             forState:(UIControlState)state
15                            completed:(nullable SDExternalCompletionBlock)completedBlock;
16 
17 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
18                             forState:(UIControlState)state
19                     placeholderImage:(nullable UIImage *)placeholder
20                            completed:(nullable SDExternalCompletionBlock)completedBlock;

同样，这五个方法全部是调用这个方法实现，作用是异步加载按钮背景图片，并且缓存：

1  - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
2                              forState:(UIControlState)state
3                      placeholderImage:(nullable UIImage *)placeholder
4                               options:(SDWebImageOptions)options
5                             completed:(nullable SDExternalCompletionBlock)completedBlock;

5.那么我们一鼓作气吧头文件中的方法给读完吧：

1 /**
2  * Cancel the current image download
3  */
4 - (void)sd_cancelImageLoadForState:(UIControlState)state;
5 
6 /**
7  * Cancel the current backgroundImage download
8  */
9 - (void)sd_cancelBackgroundImageLoadForState:(UIControlState)state;

这两个方法，功能是取消当前正在下载的button的image和backgroundImage

.M(头文件看完，我们已然明白，这个类的重点在哪里。下面我们解读.m文件)

1.首先我们看两个get方法：

 1 - (nullable NSURL *)sd_currentImageURL {
 2     NSURL *url = self.imageURLStorage[@(self.state)];
 3 
 4     if (!url) {
 5         url = self.imageURLStorage[@(UIControlStateNormal)];
 6     }
 7 
 8     return url;
 9 }
10 
11 - (nullable NSURL *)sd_imageURLForState:(UIControlState)state {
12     return self.imageURLStorage[@(state)];
13 }

1 - (SDStateImageURLDictionary *)imageURLStorage {
2     SDStateImageURLDictionary *storage = objc_getAssociatedObject(self, &imageURLStorageKey);
3     if (!storage) {
4         storage = [NSMutableDictionary dictionary];
5         objc_setAssociatedObject(self, &imageURLStorageKey, storage, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
6     }
7 
8     return storage;
9 }

typedef NSMutableDictionary<NSNumber *, NSURL *> SDStateImageURLDictionary;

①看第一个获取url的方法，首先在名为 imageURLStorage 的字典中根据state查找url，如果url为nil，则默认返回 UIControlStateNormal 状态的url。第二个方法和第一个方法功能一样。

②我们看下面的字典的懒加载方法，使用了runtime，分类中不能定义属性，但是可以用runtime的方法，添加属性。

③typedef的作用，定义一个指定key和value类型的字典。咱们以后再项目开发中，也可以这么用，更加安全和有逼格。

2.好的，下面大餐来了：

 1 - (void)sd_setImageWithURL:(nullable NSURL *)url
 2                   forState:(UIControlState)state
 3           placeholderImage:(nullable UIImage *)placeholder
 4                    options:(SDWebImageOptions)options
 5                  completed:(nullable SDExternalCompletionBlock)completedBlock {
 6     if (!url) {
 7         [self.imageURLStorage removeObjectForKey:@(state)];
 8         return;
 9     }
10     
11     self.imageURLStorage[@(state)] = url;
12     
13     __weak typeof(self)weakSelf = self;
14     [self sd_internalSetImageWithURL:url
15                     placeholderImage:placeholder
16                              options:options
17                         operationKey:[NSString stringWithFormat:@"UIButtonImageOperation%@", @(state)]
18                        setImageBlock:^(UIImage *image, NSData *imageData) {
19                            [weakSelf setImage:image forState:state];
20                        }
21                             progress:nil
22                            completed:completedBlock];
23 }

 1 - (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
 2                             forState:(UIControlState)state
 3                     placeholderImage:(nullable UIImage *)placeholder
 4                              options:(SDWebImageOptions)options
 5                            completed:(nullable SDExternalCompletionBlock)completedBlock {
 6     if (!url) {
 7         [self.imageURLStorage removeObjectForKey:@(state)];
 8         return;
 9     }
10     
11     self.imageURLStorage[@(state)] = url;
12     
13     __weak typeof(self)weakSelf = self;
14     [self sd_internalSetImageWithURL:url
15                     placeholderImage:placeholder
16                              options:options
17                         operationKey:[NSString stringWithFormat:@"UIButtonBackgroundImageOperation%@", @(state)]
18                        setImageBlock:^(UIImage *image, NSData *imageData) {
19                            [weakSelf setBackgroundImage:image forState:state];
20                        }
21                             progress:nil
22                            completed:completedBlock];
23 }

可仔细看过这两个方法的实现，不禁大失所望（纸都准备好了，你给我看这个）。原来这货也是用uiview的方法。

3.看这几个设置imageLoad和取消imageLoad的方法

 1 - (void)sd_setImageLoadOperation:(id<SDWebImageOperation>)operation forState:(UIControlState)state {
 2     [self sd_setImageLoadOperation:operation forKey:[NSString stringWithFormat:@"UIButtonImageOperation%@", @(state)]];
 3 }
 4 
 5 - (void)sd_cancelImageLoadForState:(UIControlState)state {
 6     [self sd_cancelImageLoadOperationWithKey:[NSString stringWithFormat:@"UIButtonImageOperation%@", @(state)]];
 7 }
 8 
 9 - (void)sd_setBackgroundImageLoadOperation:(id<SDWebImageOperation>)operation forState:(UIControlState)state {
10     [self sd_setImageLoadOperation:operation forKey:[NSString stringWithFormat:@"UIButtonBackgroundImageOperation%@", @(state)]];
11 }
12 
13 - (void)sd_cancelBackgroundImageLoadForState:(UIControlState)state {
14     [self sd_cancelImageLoadOperationWithKey:[NSString stringWithFormat:@"UIButtonBackgroundImageOperation%@", @(state)]];
15 }

眼熟吧，跟上面几个方法一样，都是调用UIView+WebCacheOperation的方法来在字典中进行store operation的。

??，这个类也搞定，小总结一下UIImageView和UIButton这俩分类，方法和功能类似，都是外围看门的小弟。值得学习的点有：

①利用runtime给分类添加属性。

②使用typedef自定义指定类型的字典或者数组。

??，小伙伴们，咱们UIView+WebCache见。?

SDWebImage源码解读（四）UIButton+WebCache

标签：开发 ret 数组 run 实现查找 ogr 按钮 ace

原文地址：http://www.cnblogs.com/cbios/p/7454616.html

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