如何使用Photos框架在Swift中循环浏览照片库

Question

我有一个应用程序，为我的每个票据创建一个独特的照片库。我需要找出如何循环遍历该库，以便可以逐个上传图像到服务器。我在YouTube上遵循了这些教程。（视频）我目前使用Swift作为语言。我的最终目标是拥有以下伪代码。

//I need the following for loop example
for photo in gallery
{
    uploadToServer(photo)
}

//this function works already

func uploadToServer(photo:UIImage)
{
    callRest
    postPhoto
}

这是我的代码，但我无法想出如何循环遍历它们。

let fetchOptions = PHFetchOptions()
fetchOptions.predicate = NSPredicate(format: "title = %@", self.albumName)?
let collection:PHFetchResult = PHAssetCollection.fetchAssetCollectionsWithType(.Album, subtype: .Any, options: fetchOptions)

if let first_Obj:AnyObject = collection.firstObject{
    //found the album
    self.assetCollection = collection.firstObject as PHAssetCollection
    self.albumFound = true
}
else { albumFound = false }
var i = collection.count
self.photoAssets = PHAsset.fetchAssetsInAssetCollection(self.assetCollection, options: nil)


self.photoAssets.enumerateObjectsUsingBlock{(object: AnyObject!,
    count: Int,
    stop: UnsafeMutablePointer<ObjCBool>) in

    if object is PHAsset{
        let asset = object as PHAsset
        println("Inside  If object is PHAsset, This is number 1")

        let imageSize = CGSize(width: asset.pixelWidth,
            height: asset.pixelHeight)

        /* For faster performance, and maybe degraded image */
        let options = PHImageRequestOptions()
        options.deliveryMode = .FastFormat

        imageManager.requestImageForAsset(asset,
            targetSize: imageSize,
            contentMode: .AspectFill,
            options: options,
            resultHandler: {
                (image, info)->Void in

                self.photo = image

                var defaults: NSUserDefaults = NSUserDefaults.standardUserDefaults()
                var server = defaults.objectForKey("imageServer") as String!
                var error: NSError? = nil

                var imageData = UIImageJPEGRepresentation(self.photo, 90)
                var url = NSURL(string: server)
                var request = NSMutableURLRequest(URL: url!)
                request.HTTPMethod = "POST"
                //request.setValue("multipart/form-data", forHTTPHeaderField: "Content-Type")
                request.HTTPBody = imageData

                var response: NSURLResponse? = nil

                let reply = NSURLConnection.sendSynchronousRequest(request, returningResponse:&response, error:&error)

                let results = NSString(data:reply!, encoding:NSUTF8StringEncoding)
                println("API Response: \(results)")

                /*
                /* The image is now available to us */
                self.sendPhotos(image)
                println("enum for image, This is number 2")*/


        })
    }
}

- Spikehockey75

---

继续前进吧。哪里有难点？ - matt

我在遍历什么方面遇到了麻烦，我是Swift和iOS开发的新手。我尝试循环遍历我的PHAssetCollection，但无法实现，所以我尝试循环遍历我的PHFetchResults，但同样的问题。我不确定照片框架如何工作。 - Spikehockey75

你看了关于Photos框架的WWDC视频吗？它非常简单易懂。 - matt

我已经观看了视频，刚刚又看了一遍。它没有解释如何像数组一样循环遍历图像。至少我不明白如何“获取”它们。我将在我的帖子中添加我的代码。 - Spikehockey75

@matt 经过一些研究，我使用enumerateObjectsUsingBlock编写了上述代码，它似乎运行良好，但是获取图像数据时却得到了nil。我错过了什么吗？谢谢。 - Spikehockey75

你的requestImageForAsset实现方式太疯狂了。请记住，resultHandler是异步调用的，并且对于每个图像会被调用多次。再次强调，_观看视频_。他们详细讲解了这一点。- 请注意，你的问题现在已经完全变了；你现在正在问完全不同的事情。 - matt

Answer 1

经过一些研究和Matt的指导，我终于搞清楚了。以下是做法。请确保您在主线程上执行此操作，并设置options.synchronous = true，否则可能会导致照片没有任何价值。

func getSyncPhotos()
{
    self.albumName = String(self.ticket_id!)

    let fetchOptions = PHFetchOptions()
    fetchOptions.predicate = NSPredicate(format: "title = %@", self.albumName)?
    let collection:PHFetchResult = PHAssetCollection.fetchAssetCollectionsWithType(.Album, subtype: .Any, options: fetchOptions)

    if let first_Obj:AnyObject = collection.firstObject{
        //found the album
        self.assetCollection = collection.firstObject as PHAssetCollection
        self.albumFound = true
    }
    else { albumFound = false }
    var i = collection.count
    self.photoAssets = PHAsset.fetchAssetsInAssetCollection(self.assetCollection, options: nil)
    let imageManager = PHCachingImageManager()

    self.photoAssets.enumerateObjectsUsingBlock{(object: AnyObject!,
        count: Int,
        stop: UnsafeMutablePointer<ObjCBool>) in

        if object is PHAsset{
            let asset = object as PHAsset
            println("Inside  If object is PHAsset, This is number 1")

            let imageSize = CGSize(width: asset.pixelWidth,
                height: asset.pixelHeight)

            /* For faster performance, and maybe degraded image */
            let options = PHImageRequestOptions()
            options.deliveryMode = .FastFormat
            options.synchronous = true
            imageManager.requestImageForAsset(asset,
                targetSize: imageSize,
                contentMode: .AspectFill,
                options: options,
                resultHandler: {
                     image, info in
                    self.photo = image!
                    /* The image is now available to us */
                    self.sendPhotos(self.photo)
                    println("enum for image, This is number 2")


            })
        }
    }
}

func sendPhotos(uploadImage:UIImage)
{

    var defaults: NSUserDefaults = NSUserDefaults.standardUserDefaults()
    var server = defaults.objectForKey("imageServer") as String!
    var error: NSError? = nil

    var imageData = UIImageJPEGRepresentation(uploadImage, 90)
    var url = NSURL(string: server)
    var request = NSMutableURLRequest(URL: url!)
    request.HTTPMethod = "POST"
    //request.setValue("multipart/form-data", forHTTPHeaderField: "Content-Type")
    request.HTTPBody = imageData

    var response: NSURLResponse? = nil

    let reply = NSURLConnection.sendSynchronousRequest(request, returningResponse:&response, error:&error)

    let results = NSString(data:reply!, encoding:NSUTF8StringEncoding)
    println("API Response: \(results)")
}

- Spikehockey75

---

非常感谢你，伙计！我在网上浪费了两天时间才找到这个！ - Irshad Qureshi

使用这段代码，直到所有图像都被获取之前，内存不会被释放。如果在此任务完成之前关闭视图控制器，则会导致内存泄漏。 - PinkeshGjr

Answer 2

func fetchVideoFromLibrary() {
       let fetchOptions: PHFetchOptions = PHFetchOptions()
       fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
       let fetchResult = PHAsset.fetchAssetsWithMediaType(.Video, options: fetchOptions)
       fetchResult.enumerateObjectsUsingBlock { (object, index, stop) -> Void in
           let options = PHImageRequestOptions()
           options.synchronous = true
           options.deliveryMode = .HighQualityFormat
           PHImageManager.defaultManager().requestAVAssetForVideo(object as! PHAsset, options: .None) { (avAsset, avAudioMix, dict) -> Void in
               print(avAsset)
           }
       }
   }

- Trupti

---

如何从10到20获取视频，例如我想使用分页显示视频，所以想要获取0到10、10到20等。 - Trupti