SDWebImage、YYWebImage让UIImageVie

参考：

• iOS Runtime交换对象方法和类方法探讨
• YYImage
• SDWebImage

SDWebimage解析网络动画图片的过程

1、将data转换成img

NSData *data = xxx;
UIImage *img = SDImageCacheDecodeImageData(data, @"", SDWebImageContinueInBackground, @{});

如果是动画的图，内部解析并转换成UIImage

animatedImage = [UIImage animatedImageWithImages:animatedImages duration:totalDuration / 1000.f];

SDWebimage使用本地图片展示动画图的过程

SDAnimatedImageView+SDAnimatedImage

YYWebImage使用本地图片展示动画的过程

YYAnimatedImageView+YYImage

默认让UIImageView支持YYImage的动画播放的原理就是hook掉UIImageView的setImage方法，如果YYImage里有多帧，将YYImage转换成UIImage来进行展示

#import "UIImageView+YYAutoAnim.h"
#import <objc/runtime.h>
#import "YYAnimatedImageView.h"
#import "YYImage.h"


@implementation UIImageView (YYAutoAnim)
+(void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
    Class clazz = objc_getClass("UIImageView") 
    SEL sel1 = @selector(setImage:) ;
    SEL sel2 = @selector(yy_Anim_setImage:) ;
    Method origMethod = class_getInstanceMethod(clazz, sel1);
    Method altMethod = class_getInstanceMethod(clazz, sel2);
    BOOL didAddMethod = class_addMethod(clazz,sel1,
                                        method_getImplementation(altMethod),
                                        method_getTypeEncoding(altMethod));
    
    if (didAddMethod) {
        class_replaceMethod(clazz,altSel,
                            method_getImplementation(origMethod),
                            method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, altMethod);
    }
    
 });
}
- (void)yy_Anim_setImage:(UIImage *)image {
    
    if ([image isKindOfClass:YYImage.class] && ![self isKindOfClass:YYAnimatedImageView.class]) {
        YYImage *yImage = (YYImage *)image;
        if (yImage.animatedImageFrameCount<=1) {
            [self yy_Anim_setImage:image];
        }else{
            NSMutableArray *imageList = [NSMutableArray array];
            NSTimeInterval duration = 0;
            for (NSInteger i=0; i<yImage.animatedImageFrameCount; i++) {
                [imageList addObject:[yImage animatedImageFrameAtIndex:i]];
                duration += [yImage animatedImageDurationAtIndex:i];
            }
            UIImage *animatedImg = [UIImage animatedImageWithImages:imageList duration:duration];
            [self yy_Anim_setImage:animatedImg];
        }
    }else{
        [self yy_Anim_setImage:image];
    }
}
@end