YYAnimatedImageView

一、源码分析

1、来到YYAnimatedImageView.m的- (instancetype)initWithImage:(UIImage *)image;

- (instancetype)initWithImage:(UIImage *)image {
    self = [super init];
    _runloopMode = NSRunLoopCommonModes;
    _autoPlayAnimatedImage = YES;
    self.frame = (CGRect) {CGPointZero, image.size };
    //重写了set方法
    self.image = image;
    return self;
}

2、点击.image

- (void)setImage:(UIImage *)image {
    if (self.image == image) return;
    [self setImage:image withType:YYAnimatedImageTypeImage];
}

3、点击setImage: withType:

- (void)setImage:(id)image withType:(YYAnimatedImageType)type {
    [self stopAnimating];
    if (_link) [self resetAnimated];
    _curFrame = nil;
    switch (type) {
        case YYAnimatedImageTypeNone: break;
        case YYAnimatedImageTypeImage: super.image = image; break;
        case YYAnimatedImageTypeHighlightedImage: super.highlightedImage = image; break;
        case YYAnimatedImageTypeImages: super.animationImages = image; break;
        case YYAnimatedImageTypeHighlightedImages: super.highlightedAnimationImages = image; break;
    }
    [self imageChanged];
}

4. 1 点击imageChanged

- (void)imageChanged {
    YYAnimatedImageType newType = [self currentImageType];
    id newVisibleImage = [self imageForType:newType];
    NSUInteger newImageFrameCount = 0;
    BOOL hasContentsRect = NO;
    if ([newVisibleImage isKindOfClass:[UIImage class]] &&
        [newVisibleImage conformsToProtocol:@protocol(YYAnimatedImage)]) {
        newImageFrameCount = ((UIImage<YYAnimatedImage> *) newVisibleImage).animatedImageFrameCount;
        if (newImageFrameCount > 1) {
            hasContentsRect = [((UIImage<YYAnimatedImage> *) newVisibleImage) respondsToSelector:@selector(animatedImageContentsRectAtIndex:)];
        }
    }
    if (!hasContentsRect && _curImageHasContentsRect) {
        if (!CGRectEqualToRect(self.layer.contentsRect, CGRectMake(0, 0, 1, 1)) ) {
            [CATransaction begin];
            [CATransaction setDisableActions:YES];
            self.layer.contentsRect = CGRectMake(0, 0, 1, 1);
            [CATransaction commit];
        }
    }
    _curImageHasContentsRect = hasContentsRect;
    if (hasContentsRect) {
        CGRect rect = [((UIImage<YYAnimatedImage> *) newVisibleImage) animatedImageContentsRectAtIndex:0];
        [self setContentsRect:rect forImage:newVisibleImage];
    }
    
    if (newImageFrameCount > 1) {
        [self resetAnimated];
        _curAnimatedImage = newVisibleImage;
        _curFrame = newVisibleImage;
        _totalLoop = _curAnimatedImage.animatedImageLoopCount;
        _totalFrameCount = _curAnimatedImage.animatedImageFrameCount;
        [self calcMaxBufferCount];
    }
    [self setNeedsDisplay];
    [self didMoved];
}

- (void)didMoved {
    if (self.autoPlayAnimatedImage) {
        if(self.superview && self.window) {
            [self startAnimating];
        } else {
            [self stopAnimating];
        }
    }
}

4.2、点击resetAnimated

- (void)resetAnimated {
    dispatch_once(&_onceToken, ^{
        _lock = dispatch_semaphore_create(1);
        _buffer = [NSMutableDictionary new];
        _requestQueue = [[NSOperationQueue alloc] init];
        _requestQueue.maxConcurrentOperationCount = 1;
        //CADisplayLink：基于屏幕刷新频率的; NSTimer（预先的时间点注册好了事件！）
        _link = [CADisplayLink displayLinkWithTarget:[YYWeakProxy proxyWithTarget:self] selector:@selector(step:)];
        if (_runloopMode) {
            [_link addToRunLoop:[NSRunLoop mainRunLoop] forMode:_runloopMode];
        }
        _link.paused = YES;
        
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didReceiveMemoryWarning:) name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:nil];
    });
    
    [_requestQueue cancelAllOperations];
    LOCK(
         if (_buffer.count) {
             //后台线程异步释放对象的做法
             //对象的释放  dealloc
             NSMutableDictionary *holder = _buffer;
             //清除内容了！！！
             _buffer = [NSMutableDictionary new];
             dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
                 // Capture the dictionary to global queue,
                 // release these images in background to avoid blocking UI thread.
                 [holder class];
             });
         }
    );
    _link.paused = YES;
    _time = 0;
    if (_curIndex != 0) {
        [self willChangeValueForKey:@"currentAnimatedImageIndex"];
        _curIndex = 0;
        [self didChangeValueForKey:@"currentAnimatedImageIndex"];
    }
    _curAnimatedImage = nil;
    _curFrame = nil;
    _curLoop = 0;
    _totalLoop = 0;
    _totalFrameCount = 1;
    _loopEnd = NO;
    _bufferMiss = NO;
    _incrBufferCount = 0;
}

• 点击step

//刷新频率有关
- (void)step:(CADisplayLink *)link {
    UIImage <YYAnimatedImage> *image = _curAnimatedImage;
    NSMutableDictionary *buffer = _buffer;
    UIImage *bufferedImage = nil;
    NSUInteger nextIndex = (_curIndex + 1) % _totalFrameCount;
    BOOL bufferIsFull = NO;
    
    if (!image) return;
    if (_loopEnd) { // view will keep in last frame
        [self stopAnimating];
        return;
    }
    
    NSTimeInterval delay = 0;
    if (!_bufferMiss) {
        _time += link.duration;
        delay = [image animatedImageDurationAtIndex:_curIndex];
        if (_time < delay) return;
        _time -= delay;
        if (nextIndex == 0) {
            _curLoop++;
            if (_curLoop >= _totalLoop && _totalLoop != 0) {
                _loopEnd = YES;
                [self stopAnimating];
                [self.layer setNeedsDisplay]; // let system call `displayLayer:` before runloop sleep
                return; // stop at last frame
            }
        }
        delay = [image animatedImageDurationAtIndex:nextIndex];
        if (_time > delay) _time = delay; // do not jump over frame
    }
    LOCK(
         bufferedImage = buffer[@(nextIndex)];
         if (bufferedImage) {
             if ((int)_incrBufferCount < _totalFrameCount) {
                 [buffer removeObjectForKey:@(nextIndex)];
             }
             [self willChangeValueForKey:@"currentAnimatedImageIndex"];
             _curIndex = nextIndex;
             [self didChangeValueForKey:@"currentAnimatedImageIndex"];
             _curFrame = bufferedImage == (id)[NSNull null] ? nil : bufferedImage;
             if (_curImageHasContentsRect) {
                 _curContentsRect = [image animatedImageContentsRectAtIndex:_curIndex];
                 [self setContentsRect:_curContentsRect forImage:_curFrame];
             }
             nextIndex = (_curIndex + 1) % _totalFrameCount;
             _bufferMiss = NO;
             if (buffer.count == _totalFrameCount) {
                 bufferIsFull = YES;
             }
         } else {
             _bufferMiss = YES;
         }
    )//LOCK
    
    if (!_bufferMiss) {
        [self.layer setNeedsDisplay]; // let system call `displayLayer:` before runloop sleep
    }
    
    if (!bufferIsFull && _requestQueue.operationCount == 0) { // if some work not finished, wait for next opportunity
        _YYAnimatedImageViewFetchOperation *operation = [_YYAnimatedImageViewFetchOperation new];
        operation.view = self;
        operation.nextIndex = nextIndex;
        operation.curImage = image;
        [_requestQueue addOperation:operation];
    }
}