ios – 如何使用Swift保存远程图像？

我试图用 Swift显示和保存图像.在第一击中,它在imageview上显示远程图像,第二次按下它会显示空白的imageview,而不是应该是第一次保存的本地图像.

var paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask,true)[0] as String
    var imagePath = paths.stringByAppendingPathComponent("images/\(id)/logo.jpg" )
    var checkImage = NSFileManager.defaultManager()

    if (checkImage.fileExistsAtPath(imagePath)) {
        let getimage = UIImage(contentsOfFile: imagePath)
        self.image?.image = getimage
    } else {
        dispatch_async(dispatch_get_main_queue()) {
            let getimage =  UIImage(data: NSData(contentsOfURL: NSURL(string: remoteImage)))
            UIImageJPEGRepresentation(getimage,100).writetoFile(imagePath,atomically: true)
            self.image?.image = getimage
        }
    }

编辑：这一个为我工作.

var paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,true)[0] as String
var dirPath = paths.stringByAppendingPathComponent("images/\(id)" )
var imagePath = paths.stringByAppendingPathComponent("images/\(id)/logo.jpg" )
var checkImage = NSFileManager.defaultManager()

if (checkImage.fileExistsAtPath(imagePath)) {
    let getimage = UIImage(contentsOfFile: imagePath)
    self.image?.image = getimage
} else {
    dispatch_async(dispatch_get_global_queue(disPATCH_QUEUE_PRIORITY_BACKGROUND,0)) {
        checkImage.createDirectoryAtPath(dirPath,withIntermediateDirectories: true,attributes: nil,error: nil)
        let getimage =  UIImage(data: NSData(contentsOfURL: NSURL(string: remoteImage)))
        UIImageJPEGRepresentation(getimage,atomically: true)

        dispatch_async(dispatch_get_main_queue()) {
            self.image?.image = getimage
            return
        }
    }
}

解决方法

要回答你的主要问题,你打电话给错误的UIImage初始化程序.您应该在swift 2中调用UIImage(contentsOfFile：imagePath),并在swift 3中调用UIImage(contentsOf：imagePath).

另外,看起来您正在使用dispatch_async(或swift 3中的dispatchQueue)在后台进行远程抓取,但是您将其传递给主队列,因此您实际上阻止了主/ .您应该将其分派到其中一个后台队列,然后在实际在UI中设置图像时将其分派回主队列：

Swift 3：

dispatchQueue.global(qos: dispatchQoS.background.qosClass).async {
    do {
        let data = try Data(contentsOf: URL(string: self.remoteImage)!)
        let getimage = UIImage(data: data)
        try UIImageJPEGRepresentation(getimage!,100)?.write(to: imagePath)
        dispatchQueue.main.async {
            self.image?.image = getimage
            return
        }
    }
    catch {
            return
    }
}

Swift 2：

dispatch_async(dispatch_get_global_queue(disPATCH_QUEUE_PRIORITY_BACKGROUND,0)) {
    let getimage =  UIImage(data: NSData(contentsOfURL: NSURL(string: self.remoteImage)))
    UIImageJPEGRepresentation(getimage,atomically: true)

    dispatch_async(dispatch_get_main_queue()) {
        self.image?.image = getimage
        return
    }
}

@Rob’s answer re：获取远程图像并保存它真的是最好的方法.