UIImage 是否缓存图像? [英] Does the UIImage Cache image?

问题描述

UIImage *img = [[UIImage alloc] initWithContentsOfFile:@"xx.jpg"]
UIImage *img = [UIImage imageNamed:@"xx.jpg"]

在第二种类型中，图像会被缓存吗?
而在第一种类型中，图像不会被缓存?

In the second type will the image get cached ?
Whereas the in the first type the images doesn't get cached?

推荐答案

• -initWithContentsOfFile: 创建一个没有缓存的新图像，这是一个普通的初始化方法.

  • The -initWithContentsOfFile: creates a new image without caching, it's an ordinary initialization method.

    +imageNamed: 方法使用缓存.这是来自 UIImage Reference 的文档:

    The +imageNamed: method uses cache. Here's a documentation from UIImage Reference:

    此方法在系统缓存中查找具有指定名称的图像对象，如果存在则返回该对象.如果缓存中没有匹配的图像对象，则此方法从指定文件加载图像数据，缓存它，然后返回结果对象.

    This method looks in the system caches for an image object with the specified name and returns that object if it exists. If a matching image object is not already in the cache, this method loads the image data from the specified file, caches it, and then returns the resulting object.

    UIImage 将保留加载的图像，使其保持活动状态直到内存不足导致缓存被清除.

    UIImage will retain loaded image, keeping it alive until low memory condition will cause the cache to be purged.

    Swift 更新:在 Swift 中，UIImage(named: "...") 函数是缓存图像的函数.

    Update for Swift: In Swift the UIImage(named: "...") function is the one that caches the image.

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