iOS實作簡易的長截圖

長截圖的實作原理：

實際上是將view的內容繪制成圖片，再將各個view繪制出來的圖片拼接出來，

具體代碼：

將view繪制成圖片

func getImage(in view:UIView?) -> UIImage? {
	guard let view = view else {return nil}
	let size = view.bounds.size
	UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale)
	view.layer.render(in: UIGraphicsGetCurrentContext()!)
	view.layer.contents = nil
	let image = UIGraphicsGetImageFromCurrentImageContext()
	UIGraphicsEndImageContext()
	return image
}

1.繪制狀態欄

// 先獲取狀態欄view
func getStatusBar() -> UIView? {
	if Float(UIDevice.current.systemVersion)! >= 13 {
        guard let statusBarManager = UIApplication.shared.keyWindow?.windowScene?.statusBarManager,
              let localStatusBar = statusBarManager.value(forKey: "createLocalStatusBar") as? NSObject,
              let statusBar = localStatusBar.value(forKey: "statusBar") as? UIView else {return nil}
        return statusBar
    } else {
        guard let statusBarWindow = UIApplication.shared.value(forKey: "statusBarWindow") as? UIWindow  else {return nil}
        let statusBar = statusBarWindow.value(forKey: "statusBar") as? UIView
        return statusBar
    }
}

// 再繪制成圖片
let statusBarImage = getImage(in: getStatusBar())

2.繪制導航欄(如果有的話)

if let nav = vc.navigationController { // 表示有導航欄
    let navBar = nav.navigationBar
    let navBarImage = getImage(in: navBar)
}

在某些情況下，如自定義的導航欄，則需要另外自行獲取view再來繪制

3.繪制ScrollView

繪制scrollview長圖的時候，如果直接繪制的話，那么得到的圖片就是scrollview的frame.size大小的圖片，而沒有滾動到的地方則不會繪制進去，所以要先將scrollview的size變成和contentSize一樣

func getScrollViewImage(scrollView:UIScrollView?) -> UIImage? {
    if let scroll = scrollView {
        let saveOffset = scroll.contentOffset // 保存偏移量，用于繪制圖片完成后還原
        let saveFrame = scroll.frame // 保存frame
        scroll.contentOffset = CGPoint.zero
        scroll.frame = CGRect(origin: saveFrame.origin, size: scroll.contentSize) // 設定size和contentSize一致
        
        UIGraphicsBeginImageContext(scroll.frame.size)
        UIGraphicsBeginImageContextWithOptions(CGSize(width: scroll.frame.size.width, height: scroll.frame.size.height), false, UIScreen.main.scale)
        scroll.layer.render(in: UIGraphicsGetCurrentContext()!)
        let scrollImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        scroll.contentOffset = saveOffset // 還原偏移量，否則繪制圖片之后，scrollview偏移量不正確
        scroll.frame = saveFrame // 還原frame
        return scrollImage
    }
    return nil
}

到這里，其實最難的一步已經完成了，但是這個方法也不是完美的，當這個scrollview添加到父視圖的時候是添加約束的方式來確定大小和位置的時候，使用這個方法繪制出來的圖片大小沒有問題，但是內容卻可能只有螢屏上顯示出來的部分多一點，其他部分是空白，具體原因我也不太清楚，只要在繪制成圖片之前將約束移除，繪制之后再添加回來

func getScrollViewImage(scrollView:UIScrollView?) -> UIImage? {
    if let scroll = scrollView {
        let saveOffset = scroll.contentOffset // 保存偏移量，用于繪制圖片完成后還原
        let saveFrame = scroll.frame // 保存frame
        scroll.contentOffset = CGPoint.zero
        scroll.frame = CGRect(origin: saveFrame.origin, size: scroll.contentSize) // 設定size和contentSize一致
        let layouts = scroll.superview!.constraints // 獲取的是scrollview的父容器的約束，這才是約束scrollview大小和位置的正確約束
        scroll.superview?.removeConstraints(layouts)
        
        UIGraphicsBeginImageContext(scroll.frame.size)
        UIGraphicsBeginImageContextWithOptions(CGSize(width: scroll.frame.size.width, height: scroll.frame.size.height), false, UIScreen.main.scale)
        scroll.layer.render(in: UIGraphicsGetCurrentContext()!)
        let scrollImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        scroll.contentOffset = saveOffset // 還原偏移量，否則繪制圖片之后，scrollview偏移量不正確
        scroll.frame = saveFrame // 還原frame
        scroll.superview?.addConstraints(layouts) // 還原約束
        return scrollImage
    }
    return nil
}

如果專案中集成了SnapKit的話可以用其給scrollview重新設定約束，繪制圖片結束后在還原也可以

func getScrollViewImage(scrollView:UIScrollView?) -> UIImage? {
    if let scroll = scrollView {
        
		// ......

        let layouts = scroll.superview!.constraints // 獲取的是scrollview的父容器的約束，這才是約束scrollview大小和位置的正確約束
        scroll.snp.remakeConstraints { (make) in
            make.top.left.right.equalTo(0)
            make.height.equalTo(scroll.contentSize.height)
        }
        
        // ...... 
        
        scroll.snp.removeConstraints()
        scroll.superview?.addConstraints(layouts) // 還原約束
        
        return scrollImage
    }
    return nil
}

4.拼接圖片

已經得到了所需要的各個部分的元素，這里按照上下位置將其拼接起來

func combineImages(with upImage:UIImage?, and downImage:UIImage?) -> UIImage? {
    if upImage == nil {
        return downImage
    }
    if downImage == nil {
        return upImage
    }
    guard let up = upImage,
          let down = downImage else {return nil}
    let size = CGSize(width: up.size.width, height: up.size.height + down.size.height)
    UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale)
    
    let upRect = CGRect(origin: CGPoint(x: 0, y: 0), size: up.size)
    up.draw(in: upRect)
    let downRect = CGRect(x: (up.size.width - down.size.width) / 2, y: upRect.origin.y + upRect.size.height, width: down.size.width, height: down.size.height)
    down.draw(in: downRect)
    
    let result = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return result
}

這里是圖片的上下拼接，左右拼接與這個類似，只需要計算好圖片的左右位置即可，
效果圖：