GitHub Demo

介紹

對 UIScrollView 及其子類 UITableView征绎、UICollectionView 的內(nèi)容進行長截圖。

思路

對 UIScrollView進行長截屏時是整，需要知道它的全部內(nèi)容，包括未加載未渲染的內(nèi)容。

做法是通過設(shè)置它的內(nèi)容偏移量 contentOffset挺尾， 讓 ScrollView 的內(nèi)容滑動到底部返顺，這樣便可以觸發(fā) ScrollView 中全部內(nèi)容的加載和渲染肮蛹。

用 CoreGraphics 對 ScrollView 的內(nèi)容渲染生成圖片，此時我們需要令 ScrollView 的寬高等于 它 contentSize 的真實寬高创南，在截屏結(jié)束后再恢復伦忠，因此需要提前緩存一份 ScrollView 的屬性。

問題

Q：設(shè)置 ScrollView 偏移量時稿辙，用戶看見的界面內(nèi)容會發(fā)生偏移昆码，怎么處理？

A：在設(shè)置偏移之前邻储，使用 UIView 的 func snapshotView(afterScreenUpdates afterUpdates: Bool) -> UIView? 方法對當前看見的內(nèi)容截屏（注意：此方法只會截屏已顯示加載出來的內(nèi)容赋咽，非全部），然后用 addSubview() 添加 Scrollview.superView上吨娜，蓋在 UIScrollView 之上脓匿，這樣用戶看見的就是一個假的不會變動的View。

使用：

scrollView.swContentCapture { (image) in
    // TODO:                           
}

全部代碼如下：

代碼中有詳細注釋

// Reference:  https://github.com/startry/SwViewCapture
// Notes: The 'swContentCapture(_:)' method would lose constraints of UIScrollview, we need remake its constraints after screenshot.

import UIKit

public extension UIScrollView {

    func swContentCapture (_ completionHandler: @escaping (_ capturedImage: UIImage?) -> Void) {

        // Put a fake Cover of View
        let snapShotView = self.snapshotView(afterScreenUpdates: false)
        snapShotView?.frame = CGRect(x: self.frame.origin.x, y: self.frame.origin.y, width: (snapShotView?.frame.size.width)!, height: (snapShotView?.frame.size.height)!)
        self.superview?.addSubview(snapShotView!)

        // Backup all properties of scrollview if needed
        let bakFrame     = self.frame
        let bakOffset    = self.contentOffset
        let bakSuperView = self.superview
        let bakIndex     = self.superview?.subviews.firstIndex(of: self)

        // Scroll To Bottom show all cached view
        if self.frame.size.height < self.contentSize.height {
            self.contentOffset = CGPoint(x: 0, y: self.contentSize.height - self.frame.size.height)
        }

        self.swRenderImageView({ [weak self] (capturedImage) -> Void in
            // Recover View

            let strongSelf = self!

            strongSelf.removeFromSuperview()
            strongSelf.frame = bakFrame
            strongSelf.contentOffset = bakOffset
            bakSuperView?.insertSubview(strongSelf, at: bakIndex!)

            snapShotView?.removeFromSuperview()

            completionHandler(capturedImage)
        })
    }

    private func swRenderImageView(_ completionHandler: @escaping (_ capturedImage: UIImage?) -> Void) {
        // Due to scroll to bottom, delay to wait for contentOffset refreshing.
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.6) {
            // Rebuild scrollView superView and their hold relationship
            let swTempRenderView = UIView(frame: CGRect(x: 0, y: 0, width: self.contentSize.width, height: self.contentSize.height))
            self.removeFromSuperview()
            swTempRenderView.addSubview(self)

            self.contentOffset = CGPoint.zero
            self.frame         = swTempRenderView.bounds

            // Sometimes ScrollView will Capture nothing without defer;
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
                let bounds = self.bounds
                UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
                self.layer.render(in: UIGraphicsGetCurrentContext()!)
                let capturedImage = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()

                completionHandler(capturedImage)
            }
        }
    }
}

SwViewCapture