本文的内容主要以代码为主，分析和学习了主要的类，在学习过程中添加相关的中文注释，重要且利于理解的英文注释也保留;如果有理解不对的地方，请告诉我。
KingfisherManager
/// Shared manager used by the extensions across Kingfisher.
public static let shared = KingfisherManager()
/// Cache used by this manager
//图片缓存配置
public var cache: ImageCache
/// Downloader used by this manager
//图片下载配置
public var downloader: ImageDownloader
对外接口
@discardableResult
//获取缓存图片
public func retrieveImage(with resource: Resource,
options: KingfisherOptionsInfo?,
progressBlock: DownloadProgressBlock?,
completionHandler: CompletionHandler?) -> RetrieveImageTask
{
let task = RetrieveImageTask()
//强制刷新 从网络获取图片
if let options = options, options.forceRefresh {
_ = downloadAndCacheImage(
with: resource.downloadURL,
forKey: resource.cacheKey,
retrieveImageTask: task,
progressBlock: progressBlock,
completionHandler: completionHandler,
options: options)
} else {
//从本地取图片
tryToRetrieveImageFromCache(
forKey: resource.cacheKey,
with: resource.downloadURL,
retrieveImageTask: task,
progressBlock: progressBlock,
completionHandler: completionHandler,
options: options)
}
return task
}
下载并缓存
@discardableResult
//下载并且缓存图片
func downloadAndCacheImage(with url: URL,
forKey key: String,
retrieveImageTask: RetrieveImageTask,
progressBlock: DownloadProgressBlock?,
completionHandler: CompletionHandler?,
options: KingfisherOptionsInfo?) -> RetrieveImageDownloadTask?
{
//获取下载器 并开启下载
let options = options ?? KingfisherEmptyOptionsInfo
let downloader = options.downloader
return downloader.downloadImage(with: url, retrieveImageTask: retrieveImageTask, options: options,
progressBlock: { receivedSize, totalSize in
progressBlock?(receivedSize, totalSize)
},
completionHandler: { image, error, imageURL, originalData in
let targetCache = options.targetCache
if let error = error, error.code == KingfisherError.notModified.rawValue {
// Not modified. Try to find the image from cache.
// (The image should be in cache. It should be guaranteed by the framework users.)
//如果有错误并且没有修改过URL 返回缓存图片
targetCache.retrieveImage(forKey: key, options: options, completionHandler: { (cacheImage, cacheType) -> () in
completionHandler?(cacheImage, nil, cacheType, url)
})
return
}
//图片存入本地
if let image = image, let originalData = originalData {
targetCache.store(image,
original: originalData,
forKey: key,
processorIdentifier:options.processor.identifier,
cacheSerializer: options.cacheSerializer,
toDisk: !options.cacheMemoryOnly,
completionHandler: nil)
}
completionHandler?(image, error, .none, url)
})
}
从本地取，失败后下载
func tryToRetrieveImageFromCache(forKey key: String,
with url: URL,
retrieveImageTask: RetrieveImageTask,
progressBlock: DownloadProgressBlock?,
completionHandler: CompletionHandler?,
options: KingfisherOptionsInfo?)
{
let diskTaskCompletionHandler: CompletionHandler = { (image, error, cacheType, imageURL) -> () in
completionHandler?(image, error, cacheType, imageURL)
}
let targetCache = options?.targetCache ?? cache
targetCache.retrieveImage(forKey: key, options: options,
completionHandler: { image, cacheType in
if image != nil {
//成功
diskTaskCompletionHandler(image, nil, cacheType, url)
} else if let options = options, options.onlyFromCache {
//失败，但设定只从本地取
let error = NSError(domain: KingfisherErrorDomain, code: KingfisherError.notCached.rawValue, userInfo: nil)
diskTaskCompletionHandler(nil, error, .none, url)
} else {
//失败，从网络获取
self.downloadAndCacheImage(
with: url,
forKey: key,
retrieveImageTask: retrieveImageTask,
progressBlock: progressBlock,
completionHandler: diskTaskCompletionHandler,
options: options)
}
}
)
}
ImageView+Kingfisher
加载图片
@discardableResult
public func setImage(with resource: Resource?,
placeholder: Image? = nil,
options: KingfisherOptionsInfo? = nil,
progressBlock: DownloadProgressBlock? = nil,
completionHandler: CompletionHandler? = nil) -> RetrieveImageTask
{
guard let resource = resource else {
base.image = placeholder
setWebURL(nil)
completionHandler?(nil, nil, .none, nil)
return .empty
}
var options = options ?? KingfisherEmptyOptionsInfo
//图片加载过程中是否显示placeholder
if !options.keepCurrentImageWhileLoading {
base.image = placeholder
}
//加载动画存在即开启
let maybeIndicator = indicator
maybeIndicator?.startAnimatingView()
//关联下载链接
setWebURL(resource.downloadURL)
// 默认开启加载所有GIF图片数据，显示GIF 动态图片
if base.shouldPreloadAllGIF() {
options.append(.preloadAllGIFData)
}
//调用KingfisherManager来获取图片
let task = KingfisherManager.shared.retrieveImage(
with: resource,
options: options,
progressBlock: { receivedSize, totalSize in
guard resource.downloadURL == self.webURL else {
return
}
if let progressBlock = progressBlock {
//下载进度
progressBlock(receivedSize, totalSize)
}
},
completionHandler: {[weak base] image, error, cacheType, imageURL in
DispatchQueue.main.safeAsync {
guard let strongBase = base, imageURL == self.webURL else {
return
}
self.setImageTask(nil)
guard let image = image else {
maybeIndicator?.stopAnimatingView()
completionHandler?(nil, error, cacheType, imageURL)
return
}
//动画条件判断
guard let transitionItem = options.firstMatchIgnoringAssociatedValue(.transition(.none)),
case .transition(let transition) = transitionItem, ( options.forceTransition || cacheType == .none) else
{
maybeIndicator?.stopAnimatingView()
strongBase.image = image
completionHandler?(image, error, cacheType, imageURL)
return
}
//过渡动画
#if !os(macOS)
UIView.transition(with: strongBase, duration: 0.0, options: [],
animations: { maybeIndicator?.stopAnimatingView() },
completion: { _ in
UIView.transition(with: strongBase, duration: transition.duration,
options: [transition.animationOptions, .allowUserInteraction],
animations: {
// Set image property in the animation.
transition.animations?(strongBase, image)
},
completion: { finished in
transition.completion?(finished)
completionHandler?(image, error, cacheType, imageURL)
})
})
#endif
}
})
setImageTask(task)
return task
}
加载动画实现
// MARK: - Associated Object
private var lastURLKey: Void?
private var indicatorKey: Void?
private var indicatorTypeKey: Void?
private var imageTaskKey: Void?
//加载动画视图实现
extension Kingfisher where Base: ImageView {
/// Get the image URL binded to this image view.
public var webURL: URL? {
return objc_getAssociatedObject(base, &lastURLKey) as? URL
}
fileprivate func setWebURL(_ url: URL?) {
objc_setAssociatedObject(base, &lastURLKey, url, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
/// Holds which indicator type is going to be used.
/// Default is .none, means no indicator will be shown.
public var indicatorType: IndicatorType {
get {
let indicator = (objc_getAssociatedObject(base, &indicatorTypeKey) as? Box)?.value
return indicator ?? .none
}
set {
switch newValue {
case .none:
indicator = nil
case .activity:
indicator = ActivityIndicator()
case .image(let data):
indicator = ImageIndicator(imageData: data)
case .custom(let anIndicator):
indicator = anIndicator
}
objc_setAssociatedObject(base, &indicatorTypeKey, Box(value: newValue), .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}
public fileprivate(set) var indicator: Indicator? {
get {
return (objc_getAssociatedObject(base, &indicatorKey) as? Box)?.value
}
set {
// Remove previous
if let previousIndicator = indicator {
previousIndicator.view.removeFromSuperview()
}
// Add new
if var newIndicator = newValue {
newIndicator.view.frame = base.frame
newIndicator.viewCenter = CGPoint(x: base.bounds.midX, y: base.bounds.midY)
newIndicator.view.isHidden = true
base.addSubview(newIndicator.view)
}
// Save in associated object
objc_setAssociatedObject(base, &indicatorKey, Box(value: newValue), .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}
fileprivate var imageTask: RetrieveImageTask? {
return objc_getAssociatedObject(base, &imageTaskKey) as? RetrieveImageTask
}
fileprivate func setImageTask(_ task: RetrieveImageTask?) {
objc_setAssociatedObject(base, &imageTaskKey, task, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}