iOS 11无法从MKMapView抓取屏幕

Question

我有一个应用程序，可以显示用户在MKMapView上行走的位置。当用户离开地图视图时，应用程序将抓取屏幕并将图像保存在磁盘上。直到 iOSS 10.3，这种方法总是成功的。在iOS 11.0中，屏幕抓取是空白图像。我没有收到来自 xcode 的通知，说有一些更改，我需要调整代码。

有趣的是，文本页面中的屏幕抓取仍然被成功抓取和保存。

有没有人遇到同样的问题并得到了解决方案？

到目前为止，一直成功的代码是：

override func viewWillDisappear(_ animated: Bool) {
    //Set the full file name under which the track will be saved.
    let fileBaseName = self.imageName.appending(String(describing: (self.display?.trackDate)!))
    let fileFullName = fileBaseName.appending(".png")
    //Check if the image already has been saved
    if !AuxiliaryObjects.shared.getImageFileName(with: fileFullName ) {
        //Create the sizes of the capture
        let screenRect = self.trackMapView.frame
        let screenSize = screenRect.size
        let screenScale = UIScreen.main.scale
        var grabRect = self.trackMapView.convertRegion(self.mapRegion, toRectTo: self.view)
        var heightAdjustment : CGFloat = 0.0
        //Grab the image from the screen
        UIGraphicsBeginImageContextWithOptions(screenSize, false, screenScale)
        self.trackMapView.drawHierarchy(in: screenRect, afterScreenUpdates: true)
        let myImage = UIGraphicsGetImageFromCurrentImageContext()
        grabRect.origin.x *= (myImage?.scale)!
        grabRect.origin.y *= (myImage?.scale)!
        grabRect.size.width *= (myImage?.scale)!
        grabRect.size.height *= (myImage?.scale)!
        let grabImage = (myImage?.cgImage)!.cropping(to: grabRect)
        let mapImage = UIImage(cgImage: grabImage!)
        UIGraphicsEndImageContext()
        AuxiliaryObjects.shared.save(image: mapImage, with: fileFullName, and: self.imageName)
        self.display?.displayImage = AuxiliaryObjects.shared.getImage(with: fileFullName, with: self.tableImageRect)!
    } else {
        self.display?.displayImage = AuxiliaryObjects.shared.getImage(with: fileFullName, with: self.tableImageRect)!
    }
}

Answer 1

我在Apple上提交了代码级支持请求，以获得问题的答案。苹果不支持使用drawHierarhy来抓取MapKit屏幕。要走的方法是使用 MKMapSnapshotter 实用程序创建 MKMapSnapshot，然后通过将所有地图坐标转换为查看坐标来绘制线条和注释。

由于这给我在获取镜像和正确转换坐标方面带来了一些问题，我决定使用图层方法render（in：CGContext），这为我提供了一个功能良好、非常有效的屏幕抓取。

func creatSnapshot(with fileName: String) {
    UIGraphicsBeginImageContextWithOptions(self.trackMapView.frame.size, false, UIScreen.main.scale)
    let currentContext = UIGraphicsGetCurrentContext()
    self.trackMapView.layer.render(in: currentContext!)
    let contextImage = (UIGraphicsGetImageFromCurrentImageContext())!
    UIGraphicsEndImageContext()
    let region = self.trackMapView.region
    var cropRect = self.trackMapView.convertRegion(region, toRectTo: self.trackMapView.superview)
    cropRect.origin.x *= contextImage.scale
    cropRect.origin.y *= contextImage.scale
    cropRect.size.height *= contextImage.scale
    cropRect.size.width *= contextImage.scale
    let cgMapImage = contextImage.cgImage?.cropping(to: cropRect)
    let mapImage = UIImage(cgImage: cgMapImage!)
    AuxiliaryObjects.shared.save(image: mapImage, with: fileName, and: self.imageName)
    self.displayTrack?.displayImage = AuxiliaryObjects.shared.getImage(with: fileName, with: self.tableImageRect)!
    NotificationCenter.default.post(name: self.imageSavedNotification, object: self)
}