问题：

适配iPad时，调用UIAlertController和UIActivityViewController软件崩溃。iPhone设备上软件运行正常。

错误打印如下：

Thread 1: "UIPopoverPresentationController () should have a non-nil sourceView or barButtonItem set before the presentation occurs."

Thread 1: "Your application has presented a UIAlertController () of style UIAlertControllerStyleActionSheet from purecolor.RootTabBar (). The modalPresentationStyle of a UIAlertController with this style is UIModalPresentationPopover. You must provide location information for this popover through the alert controller's popoverPresentationController. You must provide either a sourceView and sourceRect or a barButtonItem.  If this information is not known when you present the alert controller, you may provide it in the UIPopoverPresentationControllerDelegate method -prepareForPopoverPresentation."

原因：

UIAlertController和UIActivityViewController这类气泡类视图，在iPad上需要为其指定sourceView和sourceRect，以便让气泡的箭头指向sourceView。

解决：

UIAlertController在类型为actionSheet时会闪退，类型为alert时没影响。

@objc private func longPressViewAction(_ sender: Any) {guard let topVC = GAScreenUIManager.topViewController() as? LibraryViewController, topVC.className != "UIAlertController" else {return}let alert = UIAlertController(title: nil, message: tempMsg, preferredStyle: .actionSheet)if UIDevice.current.userInterfaceIdiom == .pad {var vcPoint = topVC.view.convert(self.center, to: topVC.view)vcPoint.y = vcPoint.y + UIDevice.navigationBarHeight() - topVC.collectionView.contentOffset.yalert.popoverPresentationController?.sourceView = topVC.viewalert.popoverPresentationController?.sourceRect = CGRect(x: vcPoint.x, y: vcPoint.y, width: 1, height: 1)alert.popoverPresentationController?.permittedArrowDirections = UIPopoverArrowDirection.any}let anyAction = UIAlertAction(title: "复制名称和颜色", style: .default) { action in}alert.addAction(anyAction)let cancelAction = UIAlertAction(title: "取消", style: .cancel) { action in}alert.addAction(cancelAction)topVC.present(alert, animated: true, completion: nil)
}

UIActivityViewController

private func enterActivity(_ img: UIImage) {let activity = UIActivityViewController(activityItems: [img], applicationActivities: nil)if UIDevice.current.userInterfaceIdiom == .pad {activity.popoverPresentationController?.sourceView = self.viewactivity.popoverPresentationController?.sourceRect = CGRect(x: UIScreen.main.bounds.size.width - 88, y:0 , width: 88, height: 88)activity.popoverPresentationController?.permittedArrowDirections = UIPopoverArrowDirection.any}self.present(activity, animated: true)
}

示意图：