Xcode 图像操作内存泄漏

Question

我目前正在开发的 iOS 项目遇到问题。它经历了一个过程，它必须从服务器下载图像，将它们四舍五入并将它们放在黑色背景上，最后将它们保存为文件。这会循环遍历 2000 多个不同图像的 URL，并且必须对每个 URL 进行处理。问题是某处似乎存在巨大的内存泄漏，我只是想不出如何解决它。应用程序终止前触发内存警告四次。

func getRoundedPNGDataFromData(imageData: NSData) -> NSData? {
    let Image: UIImage? = UIImage(data: imageData)!
    let ImageFrame: CGRect = CGRectMake(0, 0, Image!.size.width, Image!.size.height)
    UIGraphicsBeginImageContextWithOptions(Image!.size, false, 1.0);
    let CurrentContext: CGContextRef = UIGraphicsGetCurrentContext()
    CGContextSetFillColorWithColor(CurrentContext, UIColor.blackColor().CGColor)
    CGContextFillRect(CurrentContext, ImageFrame)
    UIBezierPath(roundedRect: ImageFrame, cornerRadius: 10.0).addClip()
    Image!.drawInRect(ImageFrame)
    let NewImage: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return UIImagePNGRepresentation(NewImage!)
}

...
var ProgressCounter: Int = 0
    for OID: String in MissingThumbnails {
    let CurrentProgress: CFloat = (CFloat(ProgressCounter) / CFloat(MissingThumbnails.count))
    dispatch_sync(dispatch_get_main_queue(), {
        progressView?.progress
        progressView?.setProgress(CurrentProgress, animated: true)
    })
    let ThumbURL: NSURL = NSURL(string: "http://\(Host):\(Port)/\(self.WebAPIThumbnailPath)".stringByReplacingOccurrencesOfString("${OID}", withString: OID, options: [], range: nil).stringByReplacingOccurrencesOfString("${ThumbnailNumber}", withString: self.padID(5), options: [], range: nil))!
    var ThumbData: NSData? = NSData(contentsOfURL: ThumbURL)
    if (ThumbData != nil) {
        if (ThumbData!.length > 0) {
                var RoundedPNG: NSData? = self.getRoundedPNGDataFromData(ThumbData!)
            if ((RoundedPNG!.writeToFile(FSTools.getDocumentSub("\(self.Structs[Paths.OBJ_THUMBNAILS])/\(OID).png"), atomically: false)) == false) {
                dispatch_sync(dispatch_get_main_queue(), {() -> Void in
                    UIApplication.sharedApplication().networkActivityIndicatorVisible = false
                    delegate?.thumbnailCacheCompleted?(false)
                })
            }
            RoundedPNG = nil
            ThumbData = nil
        }
    }
    ProgressCounter++
}

Answer 1

您需要在循环内添加一个自动释放池以允许释放自动释放的内存。

for OID: String in MissingThumbnails {
    autoreleasepool {
      /* code */ 
    }
}

当当前自动释放池范围离开时，自动释放的内存被释放，这通常发生在运行循环中。但是如果代码紧凑，运行循环没有运行，内存就不会及时释放。在每次迭代时添加显式自动释放池将允许在循环的每次迭代中回收临时自动释放内存。

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