如何在 Swift 中截取 UITableView 中选定行的屏幕截图并将其保存为 UIImage？

Question

在我的 Swift 应用程序中，我有一个 UITableView，其中包含 4 个静态单元格，然后它具有不同数量的动态单元格。我只想截取静态单元格的屏幕截图。

我找到了以下扩展：

extension UITableView {
    var capturedImage : UIImage {
        UIGraphicsBeginImageContext(contentSize);
        scrollToRow(at: NSIndexPath(row: 0, section: 0) as IndexPath, at:     UITableViewScrollPosition.top, animated: false)
        layer.render(in: UIGraphicsGetCurrentContext()!)
        let row = numberOfRows(inSection: 0)
        let numberofRowthatShowinscreen = 4
        let scrollCount = row / numberofRowthatShowinscreen

        for i in 0 ..< scrollCount  {
            scrollToRow(at: NSIndexPath(row: (i+1)*numberofRowthatShowinscreen, section: 0) as     IndexPath, at: UITableViewScrollPosition.top, animated: false)
            layer.render(in: UIGraphicsGetCurrentContext()!)
        }

        let image:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext();
        return image;
    }
}

来自这个问题How to render a whole UITableView as an UIImage in iOS?

但问题是，即使我改变了：

let numberofRowthatShowinscreen = 4

到：

let numberofRowthatShowinscreen = 3

那么它仍然会截取整个UITableView。那么有没有办法将其限制在前 4 行？

Answer 1

在您的示例代码中，您将在图像上下文中呈现表格视图的图层。这将始终对整个表视图进行快照。您可以听取评论者的建议并在快照之前调整表格视图的单元格。或者您可以对要渲染的单元格的图层进行快照。例如：

extension UITableView
{
    func snapshotRows(at indexPaths: Set<IndexPath>) -> UIImage?
    {
        guard !indexPaths.isEmpty else { return nil }
        var rect = self.rectForRow(at: indexPaths.first!)
        for indexPath in indexPaths
        {
            let cellRect = self.rectForRow(at: indexPath)
            rect = rect.union(cellRect)
        }

        UIGraphicsBeginImageContextWithOptions(rect.size, false, 0.0)
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        for indexPath in indexPaths
        {
            let cell = self.cellForRow(at: indexPath)
            cell?.layer.bounds.origin.y = self.rectForRow(at: indexPath).origin.y - rect.minY
            cell?.layer.render(in: context)
            cell?.layer.bounds.origin.y = 0
        }

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

用法：

let image = tableView.snapshotRows(at: Set([IndexPath(row: 0, section: 0), IndexPath(row: 0, section: 1)]))

只会对特定单元格进行快照。正如另一篇文章的答案所说，这仅适用于重复使用单元格的可见单元格。