 
     override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)
-        DispatchQueue.main.async {  // 放在下一个Runtime周期，对所有显示出来的CollectionViewCell中的Checkbox进行布局
+        // 放在下一个Runloop周期，对所有显示出来的CollectionViewCell中的Checkbox进行布局
+        DispatchQueue.main.async {
             self._photosDisplayView.delegate?.scrollViewDidScroll?(self._photosDisplayView)
         }
     }

        fileprivate lazy var _contentViewForCancel: UIView = {
            let view = UIView()
            view.layer.masksToBounds = true
            view.layer.cornerRadius = photosSheetCorners
            view.autoresizingMask = .flexibleWidth
            return view
        }()

        // Send Photo
        fileprivate lazy var _sendPhotoBtn: _ActionItem = {
            let action = Action(title: "", tintColor: .green, action: { [weak self] in
                self?._sendPhotosAction()
            })
            let view = _ActionItem(action: action)

extension PhotosSheet.ContentController {
    func show(from viewController: UIViewController) {
        let height = _expectHeight
        let expireY = viewController.view.bounds.height - PhotosSheet.actionSheetVerticalMargin - height
        view.frame = CGRect(x: PhotosSheet.actionSheetHorizontalMargin, y: viewController.view.bounds.height, width: viewController.view.bounds.width - 2 * PhotosSheet.actionSheetHorizontalMargin, height: height)
        viewController.addChildViewController(self)
        viewController.view.addSubview(view)
        UIView.animate(withDuration: 0.25) {
