在 Swift 2 中拍摄照片后显示缩略图

Posted 2023-03-08

【中文标题】在 Swift 2 中拍摄照片后显示缩略图

【英文标题】：Displaying thumbnail after photo shoot in Swift 2

【发布时间】：2015-12-23 21:06:43

【问题描述】：

当尝试加载和显示刚刚拍摄的照片的缩略图时：

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
                
            )
        
    

ma​​keSelectedItemButton() 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)

        
    )

而 PhotoHelper().getThumbnailWithIdentifer 是：

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)
    

这会使按钮在照片制作后至少显示 5 秒。使用旧照片执行时，相同的功能可以快速且按预期工作。这里有什么问题？

【参考方案1】：

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，然后您可以尝试使用占位符缩略图图像，直到实际缩略图返回？

【讨论】：

对不起，我很久以前用 dispatch_after 解决了这个问题。我不知道您的解决方案是否有效，但谢谢！