Uiview 在Swift 2中拍摄照片后显示缩略图

当尝试加载和显示刚刚拍摄的照片的缩略图时，如下所示：

func photom(){

    if let videoConnection = self.stillImageOutput.connectionWithMediaType(AVMediaTypeVideo) {

        self.stillImageOutput.captureStillImageAsynchronouslyFromConnection(videoConnection) { (imageDataSampleBuffer, error) -> Void in

            let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer)
            let lPhoto = UIImage(data: imageData)
            var imageIdentifier: String?

            PHPhotoLibrary.sharedPhotoLibrary().performChanges({ () -> Void in

                let changeRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(lPhoto!)
                let placeHolder = changeRequest.placeholderForCreatedAsset
                imageIdentifier = placeHolder!.localIdentifier

            }, completionHandler: { success, error in

                if success {

                    self.currentSelectedID = imageIdentifier!
                    self.makeSelectedItemButton(0)

                    return
                }
            })
        }
    }
}

其中makeSelectedItemButton（）是：

func makeSelectedItemButton(layConst: CGFloat){

    if let selButto = view.viewWithTag(6){
        selButto.removeFromSuperview()
    }

    PhotoHelper().getThumbnailWithIdentifer(currentSelectedID, groesse: CGSize(width: cellHocR ,height: cellHocR), completion: { (image) -> Void in

        if image != nil {
            let libView = UIImageView()

            libView.frame = CGRectMake(self.abstanR, self.abstanR, 22, 22)
            libView.layer.cornerRadius = 11
            libView.clipsToBounds = true
            libView.contentMode = .ScaleAspectFill
            libView.image = image

            let libButton = UIButton()
            libButton.backgroundColor = UIColor.clearColor()
            libButton.tag = 6
            libButton.frame = CGRectMake(0+layConst, self.view.frame.height-self.cellHocR, self.cellHocR, self.cellHocR)
            libButton.addTarget(self, action: "libTap:", forControlEvents: .TouchUpInside)
            libButton.insertSubview(libView, atIndex: 0)
            self.view.addSubview(libButton)

        }
    })
}

func getThumbnailWithIdentifer(localIdentifier:String, groesse: CGSize, completion: (image:UIImage?) -> Void) {

    let manager = PHImageManager.defaultManager()
    let fetchOptions = PHFetchOptions()
    fetchOptions.predicate = NSPredicate(format: "mediaType == %d", PHAssetMediaType.Image.rawValue)

    let fetchResults = PHAsset.fetchAssetsWithLocalIdentifiers([localIdentifier], options: fetchOptions)

    if fetchResults.count > 0 {

        if let imageAsset = fetchResults.objectAtIndex(0) as? PHAsset {

            let requestOptions = PHImageRequestOptions()
            requestOptions.synchronous = true
            requestOptions.deliveryMode = .HighQualityFormat
            manager.requestImageForAsset(imageAsset, targetSize: groesse, contentMode: .AspectFit, options: requestOptions, resultHandler: { (image, info) -> Void in
                completion(image: image)
                print(image!.size)
            })

        } else {

            completion(image: nil)
        }

    } else {

        completion(image: nil)
    }
}

和PhotoHelper（）。getThumbnailWithIdentifer是：

func makeSelectedItemButton(layConst: CGFloat){

    if let selButto = view.viewWithTag(6){
        selButto.removeFromSuperview()
    }

    PhotoHelper().getThumbnailWithIdentifer(currentSelectedID, groesse: CGSize(width: cellHocR ,height: cellHocR), completion: { (image) -> Void in

        if image != nil {
            let libView = UIImageView()

            libView.frame = CGRectMake(self.abstanR, self.abstanR, 22, 22)
            libView.layer.cornerRadius = 11
            libView.clipsToBounds = true
            libView.contentMode = .ScaleAspectFill
            libView.image = image

            let libButton = UIButton()
            libButton.backgroundColor = UIColor.clearColor()
            libButton.tag = 6
            libButton.frame = CGRectMake(0+layConst, self.view.frame.height-self.cellHocR, self.cellHocR, self.cellHocR)
            libButton.addTarget(self, action: "libTap:", forControlEvents: .TouchUpInside)
            libButton.insertSubview(libView, atIndex: 0)
            self.view.addSubview(libButton)

        }
    })
}

func getThumbnailWithIdentifer(localIdentifier:String, groesse: CGSize, completion: (image:UIImage?) -> Void) {

    let manager = PHImageManager.defaultManager()
    let fetchOptions = PHFetchOptions()
    fetchOptions.predicate = NSPredicate(format: "mediaType == %d", PHAssetMediaType.Image.rawValue)

    let fetchResults = PHAsset.fetchAssetsWithLocalIdentifiers([localIdentifier], options: fetchOptions)

    if fetchResults.count > 0 {

        if let imageAsset = fetchResults.objectAtIndex(0) as? PHAsset {

            let requestOptions = PHImageRequestOptions()
            requestOptions.synchronous = true
            requestOptions.deliveryMode = .HighQualityFormat
            manager.requestImageForAsset(imageAsset, targetSize: groesse, contentMode: .AspectFit, options: requestOptions, resultHandler: { (image, info) -> Void in
                completion(image: image)
                print(image!.size)
            })

        } else {

            completion(image: nil)
        }

    } else {

        completion(image: nil)
    }
}

---

这会导致按钮在拍摄照片后至少5秒显示。当使用旧照片时，相同的功能运行得很快，并且与预期的一样。这里有什么问题？

由于getThumbnailWithIdentifer中的以下行，您是否正在等待：

requestOptions.synchronous = true

---

您可以将其更改为

false

，并尝试使用占位符缩略图图像，直到实际缩略图返回为止？

对不起，我很久以前就通过调度解决了这个问题。我不知道你的解决方案是否有效，但谢谢你！