如何在使用AVAssetExportSession保存视频时启动进度

import AVFoundation

func saveVideoWithProgress(url: URL, outputURL: URL, progressHandler: @escaping (Float) -> Void, completionHandler: @escaping (Bool, Error?) -> Void) {
    let asset = AVURLAsset(url: url)
    guard let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetHighestQuality) else {
        completionHandler(false, nil)
        return
    }
    
    exportSession.outputURL = outputURL
    exportSession.outputFileType = .mp4
    
    // 设置导出会话的输出文件的属性，如视频的分辨率、码率、帧率等
    
    exportSession.exportAsynchronously {
        switch exportSession.status {
        case .completed:
            completionHandler(true, nil)
        case .failed:
            completionHandler(false, exportSession.error)
        case .cancelled:
            completionHandler(false, nil)
        default:
            break
        }
    }
    
    // 监听导出进度的更新
    let timer = Timer(timeInterval: 0.1, repeats: true) { _ in
        let progress = exportSession.progress
        progressHandler(progress)
        
        if progress >= 1.0 {
            timer.invalidate()
        }
    }
    RunLoop.current.add(timer, forMode: .default)
}