iOS 8.0推出了UIAlertController来替代UIActionSheet。不幸的是，Apple没有添加任何关于如何呈现它的信息。我在hayaGeek的博客中找到了一个示例，但在iPad上似乎无法正常工作，视图完全错位：
错位：
正确：
我使用以下代码将其展示在界面上：
let alert = UIAlertController()
// setting buttons
self.presentModalViewController(alert, animated: true)
有没有其他方法可以在iPad上添加它？或者苹果只是忘记了iPad，还是尚未实现？
您可以使用 UIPopoverPresentationController 来从弹出窗口中展示一个 UIAlertController。
您可以使用 UIPopoverPresentationController 从弹出视图中呈现一个 UIAlertController。
UIViewController *self; // code assumes you're in a view controller
UIButton *button; // the button you want to show the popup sheet from
UIAlertController *alertController;
UIAlertAction *destroyAction;
UIAlertAction *otherAction;
alertController = [UIAlertController alertControllerWithTitle:nil
message:nil
preferredStyle:UIAlertControllerStyleActionSheet];
destroyAction = [UIAlertAction actionWithTitle:@"Remove All Data"
style:UIAlertActionStyleDestructive
handler:^(UIAlertAction *action) {
// do destructive stuff here
}];
otherAction = [UIAlertAction actionWithTitle:@"Blah"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction *action) {
// do something here
}];
// note: you can control the order buttons are shown, unlike UIActionSheet
[alertController addAction:destroyAction];
[alertController addAction:otherAction];
[alertController setModalPresentationStyle:UIModalPresentationPopover];
UIPopoverPresentationController *popPresenter = [alertController
popoverPresentationController];
popPresenter.sourceView = button;
popPresenter.sourceRect = button.bounds;
[self presentViewController:alertController animated:YES completion:nil];
虽然有很多关于Swift 4.2的博客可供参考，但在这里编辑可能可以节省您的时间。
if let popoverController = yourAlert.popoverPresentationController {
popoverController.sourceView = self.view //to set the source of your alert
popoverController.sourceRect = CGRect(x: self.view.bounds.midX, y: self.view.bounds.midY, width: 0, height: 0) // you can set this as per your requirement.
popoverController.permittedArrowDirections = [] //to hide the arrow of any particular direction
}
在iPad上，使用新的UIPopoverPresentationController，警报将显示为弹出窗口，需要指定一个锚点来呈现弹出窗口，可以使用以下方法之一：
为了指定锚点，您需要获取对UIAlertController的UIPopoverPresentationController的引用，并设置其中一个属性如下：
alertController.popoverPresentationController.barButtonItem = button;
示例代码：
UIAlertAction *actionDelete = nil;
UIAlertAction *actionCancel = nil;
// create action sheet
UIAlertController *alertController = [UIAlertController
alertControllerWithTitle:actionTitle message:nil
preferredStyle:UIAlertControllerStyleActionSheet];
// Delete Button
actionDelete = [UIAlertAction
actionWithTitle:NSLocalizedString(@"IDS_LABEL_DELETE", nil)
style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action) {
// Delete
// [self deleteFileAtCurrentIndexPath];
}];
// Cancel Button
actionCancel = [UIAlertAction
actionWithTitle:NSLocalizedString(@"IDS_LABEL_CANCEL", nil)
style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
// cancel
// Cancel code
}];
// Add Cancel action
[alertController addAction:actionCancel];
[alertController addAction:actionDelete];
// show action sheet
alertController.popoverPresentationController.barButtonItem = button;
alertController.popoverPresentationController.sourceView = self.view;
[self presentViewController:alertController animated:YES
completion:nil];
在 Swift 2 中，您想要执行类似以下的操作才能在 iPhone 和 iPad 上正确显示：
func confirmAndDelete(sender: AnyObject) {
guard let button = sender as? UIView else {
return
}
let alert = UIAlertController(title: NSLocalizedString("Delete Contact?", comment: ""), message: NSLocalizedString("This action will delete all downloaded audio files.", comment: ""), preferredStyle: .ActionSheet)
alert.modalPresentationStyle = .Popover
let action = UIAlertAction(title: NSLocalizedString("Delete", comment: ""), style: .Destructive) { action in
EarPlaySDK.deleteAllResources()
}
let cancel = UIAlertAction(title: NSLocalizedString("Cancel", comment: ""), style: .Cancel) { action in
}
alert.addAction(cancel)
alert.addAction(action)
if let presenter = alert.popoverPresentationController {
presenter.sourceView = button
presenter.sourceRect = button.bounds
}
presentViewController(alert, animated: true, completion: nil)
}
如果您不设置presentor，那么在iPad上的-[UIPopoverPresentationController presentationTransitionWillBegin]方法中会出现异常，错误信息如下:
Fatal Exception: NSGenericException 您的应用程序已经展示了一个样式为UIAlertControllerStyleActionSheet的UIAlertController (<UIAlertController: 0x17858a00>)。具有此样式的UIAlertController的modalPresentationStyle是UIModalPresentationPopover。对于这个popover，您必须通过警报控制器的popoverPresentationController提供位置信息。您必须提供sourceView和sourceRect或barButtonItem之一。如果在呈现警报控制器时不知道此信息，则可以在UIPopoverPresentationControllerDelegate方法-prepareForPopoverPresentation中提供它。
Swift 5
我在 iPhone 上使用了 "actionsheet" 样式，在 iPad 上使用了 "alert" 样式。iPad 显示在屏幕中央，无需指定 sourceView 或将视图固定在任何位置。
var alertStyle = UIAlertController.Style.actionSheet
if (UIDevice.current.userInterfaceIdiom == .pad) {
alertStyle = UIAlertController.Style.alert
}
let alertController = UIAlertController(title: "Your title", message: nil, preferredStyle: alertStyle)
编辑：根据ShareToD的建议，更新了过时的“ UI_USER_INTERFACE_IDIOM（）== UIUserInterfaceIdiom.pad”检查
针对Swift 3.0及以上版本的更新
let actionSheetController: UIAlertController = UIAlertController(title: "SomeTitle", message: nil, preferredStyle: .actionSheet)
let editAction: UIAlertAction = UIAlertAction(title: "Edit Details", style: .default) { action -> Void in
print("Edit Details")
}
let deleteAction: UIAlertAction = UIAlertAction(title: "Delete Item", style: .default) { action -> Void in
print("Delete Item")
}
let cancelAction: UIAlertAction = UIAlertAction(title: "Cancel", style: .cancel) { action -> Void in }
actionSheetController.addAction(editAction)
actionSheetController.addAction(deleteAction)
actionSheetController.addAction(cancelAction)
// present(actionSheetController, animated: true, completion: nil) // doesn't work for iPad
actionSheetController.popoverPresentationController?.sourceView = yourSourceViewName // works for both iPhone & iPad
present(actionSheetController, animated: true) {
print("option menu presented")
}
Swift 4及以上版本
我已经创建了一个扩展
extension UIViewController {
public func addActionSheetForiPad(actionSheet: UIAlertController) {
if let popoverPresentationController = actionSheet.popoverPresentationController {
popoverPresentationController.sourceView = self.view
popoverPresentationController.sourceRect = CGRect(x: self.view.bounds.midX, y: self.view.bounds.midY, width: 0, height: 0)
popoverPresentationController.permittedArrowDirections = []
}
}
}
使用方法：
let actionSheetVC = UIAlertController(title: "Title", message: nil, preferredStyle: .actionSheet)
addActionSheetForiPad(actionSheet: actionSheetVC)
present(actionSheetVC, animated: true, completion: nil)
2018年更新
我的一个应用因为这个原因被拒绝，解决方法是将操作表改为警告框。
非常有效，并且通过了App Store的测试。
可能不适合每个人，但我希望这能够帮助一些人快速摆脱困境。
Swift 4.2 您可以使用以下条件：
let alert = UIAlertController(title: nil, message: nil, preferredStyle: UIDevice.current.userInterfaceIdiom == .pad ? .alert : .actionSheet)
适用于iPad和iPhone。
对于iPhone，操作表将如常显示；对于iPad，它会显示在按钮下方。
actionSheet.popoverPresentationController?.sourceView = fooButton
actionSheet.popoverPresentationController?.sourceRect = fooButton.bounds
在iPhone上，操作表将像常规情况下一样显示；而在iPad上，它将居中显示在屏幕/视图中。
actionSheet.popoverPresentationController?.sourceView = view
actionSheet.popoverPresentationController?.sourceRect = CGRect(x: view.bounds.midX, y: view.bounds.midY, width: 0, height: 0)
actionSheet.popoverPresentationController?.permittedArrowDirections = []
NSString *text = self.contentTextView.text;
NSArray *items = @[text];
UIActivityViewController *activity = [[UIActivityViewController alloc]
initWithActivityItems:items
applicationActivities:nil];
activity.excludedActivityTypes = @[UIActivityTypePostToWeibo];
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
//activity.popoverPresentationController.sourceView = shareButtonBarItem;
activity.popoverPresentationController.barButtonItem = shareButtonBarItem;
[self presentViewController:activity animated:YES completion:nil];
}
[self presentViewController:activity animated:YES completion:nil];