未显示的视图的屏幕截图 [英] Screenshot of a view without displaying it

问题描述

我正在尝试在显示 MyFirstViewController 时截取 MySecondViewController.view 的屏幕截图.我不希望 MySecondViewController 随时出现在屏幕上.这可能吗?

I am trying to take a screenshot of a MySecondViewController.view while MyFirstViewController is displayed. I don't want MySecondViewController to appear on the screen at any moment. Is that possible?

这是我当前在 MyFirstViewController 函数中的代码:

Here is my current code inside a function of MyFirstViewController:

func createPreview() {
    let mySecondViewController = self.storyboard!.instantiateViewController(withIdentifier: "MySecondViewController")
    self.navigationController?.pushViewController(mySecondViewController, animated: false)
    let snapshot = mySecondViewController.view.snapshot()
    self.navigationController?.popViewController(animated: false)
}

这是我正在使用的 UIView 扩展:

Here is the UIView extension I am using:

func snapshot() -> UIImage {
    UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
    drawHierarchy(in: self.bounds, afterScreenUpdates: true)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image!
}

使用此代码，snapshot 变量包含具有良好尺寸的不可见图片.我认为它是在视图从导航控制器中弹出后截取屏幕截图.

With this code, the snapshot variable contains an invisible picture with the good dimensions. I think it is taking the screenshot after the view has been popped out of the navigation controller.

如果我尝试将 afterScreenUpdates 值设置为 false，那么结果是相同的.然后，我认为它是在导航控制器中推送视图之前截取屏幕截图.

If I try setting the afterScreenUpdates value to false, then the result is the same. Then, I think it is taking the screenshot before the view has been pushed in the navigation controller.

推荐答案

我找到了我要找的东西.

I've found what I was looking for.

这是新代码:

func createPreview() {
    let mySecondViewController = self.storyboard!.instantiateViewController(withIdentifier: "MySecondViewController")
    let snapshot = mySecondViewController.view.snapshot()
}

extension UIView {
    func snapshot() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, self.isOpaque, UIScreen.main.scale)
        layer.render(in: UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image!
    }
}

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