ios – UIAlertController崩溃(iPad)

当我使用UIAlertController,它可以在iPhone 6模拟器上运行良好,但在iPad模拟器上崩溃.

我的问题,当点击“分享”,那么它可能会崩溃.
我该怎么解决？

这是我的代码：

override func tableView(tableView: UITableView,editActionsForRowATindexPath indexPath: NSIndexPath) -> [AnyObject] {

    var shareAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default,title: "Share",handler: { (action:UITableViewRowAction!,indexPath:NSIndexPath!) -> Void in

        let shareMenu = UIAlertController(title: nil,message: "Share using",preferredStyle: .ActionSheet)
        let twitterAction = UIAlertAction(title: "Twitter",style: UIAlertActionStyle.Default,handler: nil)
        let facebookAction = UIAlertAction(title: "Facebook",handler: nil)
        let emailAction = UIAlertAction(title: "Email",handler: nil)
        let cancelAction = UIAlertAction(title: "Cancel",style: UIAlertActionStyle.Cancel,handler: nil)

        shareMenu.addAction(twitterAction)
        shareMenu.addAction(facebookAction)
        shareMenu.addAction(emailAction)
        shareMenu.addAction(cancelAction)

        self.presentViewController(shareMenu,animated: true,completion: nil)
        }
    )

Xcode显示此消息：

******TerminaTing app due to uncaught exception 'NSGenericException',reason: 'Your application has presented a UIAlertController (<UIAlertController: 0xaf71c80>) of style UIAlertControllerStyleActionSheet. 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[![enter image description here][1]][1] present the alert controller,you may provide it in the UIPopoverPresentationControllerDelegate method -prepareForPopoverPresentation.'
*** First throw call stack:
(
    0   CoreFoundation                      0x0023c746 __exceptionPreprocess + 182
    1   libobjc.A.dylib                     0x01c7aa97 objc_exception_throw + 44
    2   UIKit                               0x012c4062 -[UIPopoverPresentationController presentationTransitionWillBegin] + 3086
    3   UIKit                               0x00bda174 __71-[UIPresentationController _initViewHierarchyForPresentationSuperview:]_block_invoke + 1549
    4   UIKit                               0x00bd8247 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 198
    5   UIKit                               0x00c0d31b __40+[UIViewController _scheduleTransition:]_block_invoke + 18
    6   UIKit                               0x00ac6862 ___afterCACommitHandler_block_invoke + 15
    7   UIKit                               0x00ac680d _applyBlockToCFArrayCopiedToStack + 415
    8   UIKit                               0x00ac6622 _afterCACommitHandler + 549
    9   CoreFoundation                      0x0015d86e __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
    10  CoreFoundation                      0x0015d7b0 __CFRunLoopDoObservers + 400
    11  CoreFoundation                      0x001531ea __CFRunLoopRun + 1226
    12  CoreFoundation                      0x00152a5b CFRunLoopRunSpecific + 443
    13  CoreFoundation                      0x0015288b CFRunLoopRunInMode + 123
    14  Graphicsservices                    0x047b82c9 GSEventRunModal + 192
    15  Graphicsservices                    0x047b8106 GSEventRun + 104
    16  UIKit                               0x00a9c106 UIApplicationMain + 1526
    17  Mars I                              0x0001c724 main + 180
    18  libdyld.dylib                       0x02392ac9 start + 1
    19  ???                                 0x00000001 0x0 + 1
)
libc++abi.dylib: terminaTing with uncaught exception of type NSException******