UIKit新手求助：如何在Xcode中通过PHImageRequestID显示图片？

核心说明 #

PHImageRequestID只是PHImageManager发起请求时的标识，不能直接用它获取图片，你需要先拿到拍摄的Live Photo对应的PHAsset（相册资源对象），再通过PHImageManager请求资源并显示。

步骤1：拍摄后保存Live Photo并获取PHAsset #

在AVCam的AVCapturePhotoCaptureDelegate代理方法里，保存Live Photo到相册的同时，获取刚生成的PHAsset（比RequestID更实用）：

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
    guard error == nil else { return }
    
    // 保存Live Photo到系统相册
    PHPhotoLibrary.shared().performChanges({
        let creationRequest = PHAssetCreationRequest.forLivePhoto()
        let resourceOptions = PHAssetResourceCreationOptions()
        
        // 添加Live Photo的静态图片资源
        if let imageData = photo.fileDataRepresentation() {
            creationRequest.addResource(with: .photo, data: imageData, options: resourceOptions)
        }
        // 添加Live Photo的视频资源
        if let videoURL = photo.livePhotoMovieFileURL {
            creationRequest.addResource(with: .pairedVideo, fileURL: videoURL, options: resourceOptions)
        }
    }) { [weak self] success, error in
        guard success, error == nil else { return }
        
        // 抓取最新保存的Live Photo Asset
        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        fetchOptions.fetchLimit = 1
        let livePhotos = PHAsset.fetchAssets(with: .livePhoto, options: fetchOptions)
        
        if let latestAsset = livePhotos.firstObject {
            self?.latestLivePhotoAsset = latestAsset // 保存到全局变量
            self?.showPhotoButton.isHidden = false // 显示查看按钮
        }
    }
}

提前在类里定义变量：private var latestLivePhotoAsset: PHAsset?

步骤2：添加拍摄完成后的查看按钮 #

在界面初始化时添加按钮，默认隐藏，拍摄完成后显示：

// 初始化查看按钮
private func setupShowPhotoButton() {
    let showButton = UIButton(type: .system)
    showButton.setTitle("查看刚拍的Live Photo", for: .normal)
    showButton.addTarget(self, action: #selector(showLatestLivePhotoTapped), for: .touchUpInside)
    showButton.isHidden = true
    showButton.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(showButton)
    
    // 布局按钮（底部居中）
    NSLayoutConstraint.activate([
        showButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        showButton.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -20)
    ])
    
    self.showPhotoButton = showButton
}

类里定义按钮变量：private var showPhotoButton: UIButton?

步骤3：按钮点击后显示Live Photo #

用PHLivePhotoView来显示Live Photo（支持动态播放），点击可关闭：

@objc private func showLatestLivePhotoTapped() {
    guard let asset = latestLivePhotoAsset else { return }
    
    let requestOptions = PHLivePhotoRequestOptions()
    requestOptions.deliveryMode = .highQualityFormat // 请求高质量资源
    
    // 请求Live Photo资源
    PHImageManager.default().requestLivePhoto(for: asset, targetSize: view.bounds.size, contentMode: .aspectFit, options: requestOptions) { [weak self] livePhoto, info in
        guard let self = self, let livePhoto = livePhoto else { return }
        
        // 切到主线程更新UI
        DispatchQueue.main.async {
            let livePhotoView = PHLivePhotoView(frame: self.view.bounds)
            livePhotoView.livePhoto = livePhoto
            livePhotoView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
            livePhotoView.isUserInteractionEnabled = true
            
            // 添加点击关闭手势
            let tapToClose = UITapGestureRecognizer(target: self, action: #selector(self.hideLivePhotoView))
            livePhotoView.addGestureRecognizer(tapToClose)
            
            self.view.addSubview(livePhotoView)
        }
    }
}

@objc private func hideLivePhotoView(sender: UITapGestureRecognizer) {
    sender.view?.removeFromSuperview()
}

关键注意点 #

• 所有UI操作必须在主线程执行，避免界面卡顿或崩溃
• 显示Live Photo必须用PHLivePhotoView，普通UIImageView只能显示静态帧
• 若你已经持有PHImageRequestID，它的作用是取消请求（调用PHImageManager.default().cancelImageRequest(requestID)），而非直接获取图片

内容的提问来源于stack exchange，提问作者kaynmanhngen