同样的问题也出现在我的项目中，然后我找到了解决方案，在iPad中打开UIActivityViewController，我们必须使用UIPopoverController

下面是在iPhone和iPad上使用它的代码:

//to attach the image and text with sharing 
UIImage *image=[UIImage imageNamed:@"giraffe.png"];
NSString *str=@"Image form My app";
NSArray *postItems=@[str,image];

UIActivityViewController *controller = [[UIActivityViewController alloc] initWithActivityItems:postItems applicationActivities:nil];

//if iPhone
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
    [self presentViewController:controller animated:YES completion:nil];
}
//if iPad
else {
    // Change Rect to position Popover
    UIPopoverController *popup = [[UIPopoverController alloc] initWithContentViewController:controller];
    [popup presentPopoverFromRect:CGRectMake(self.view.frame.size.width/2, self.view.frame.size.height/4, 0, 0)inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
}

对于swift 4.2 / swift 5

func openShareDilog() {
    let text = "share text will goes here"

    // set up activity view controller
    let textToShare = [text]
    let activityViewController = UIActivityViewController(activityItems: textToShare, applicationActivities: nil)
    activityViewController.excludedActivityTypes = [.airDrop]

    if let popoverController = activityViewController.popoverPresentationController {
        popoverController.sourceRect = CGRect(x: UIScreen.main.bounds.width / 2, y: UIScreen.main.bounds.height / 2, width: 0, height: 0)
        popoverController.sourceView = self.view
        popoverController.permittedArrowDirections = UIPopoverArrowDirection(rawValue: 0)
    }

    self.present(activityViewController, animated: true, completion: nil)
}

对于Swift 2.0。我发现，如果你试图将弹出窗口锚定在iPad上的共享按钮上，这种方法是有效的。这假设您已经在工具栏中为共享按钮创建了一个出口。

func share(sender: AnyObject) {
    let firstActivityItem = "test"

    let activityViewController = UIActivityViewController(activityItems: [firstActivityItem], applicationActivities: nil)

    if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.Phone {
        self.presentViewController(activityViewController, animated: true, completion: nil)
    }
    else {            
        if activityViewController.respondsToSelector("popoverPresentationController") {
            activityViewController.popoverPresentationController!.barButtonItem = sender as? UIBarButtonItem
            self.presentViewController(activityViewController, animated: true, completion: nil)
        }

    }
}

在Swift修复这个iPad，最好的方法是这样做，我发现。

    let things = ["Things to share"]
    let avc = UIActivityViewController(activityItems:things, applicationActivities:nil)
    avc.setValue("Subject title", forKey: "subject")
    avc.completionWithItemsHandler = {
        (s: String!, ok: Bool, items: [AnyObject]!, err:NSError!) -> Void in
    }

    self.presentViewController(avc, animated:true, completion:nil)
    if let pop = avc.popoverPresentationController {
        let v = sender as! UIView // sender would be the button view tapped, but could be any view
        pop.sourceView = v
        pop.sourceRect = v.bounds
    }

Swift = ios7/ ios8

let activityViewController = UIActivityViewController(activityItems: sharingItems, applicationActivities: nil)

//if iPhone
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.Phone) {
    // go on..
} else {
    //if iPad
    if activityViewController.respondsToSelector(Selector("popoverPresentationController")) {
        // on iOS8
        activityViewController.popoverPresentationController!.barButtonItem = self.shareButtonItem;
    }
}
self.presentViewController(activityViewController, animated: true, completion: nil)

我看到很多人在使用Swift代码时对iPhone/iPad等进行硬编码。

这是不需要的，你必须使用语言功能。下面的代码假设你将使用一个UIBarButtonItem，并将在iPhone和iPad上工作。

@IBAction func share(sender: AnyObject) {
    let vc = UIActivityViewController(activityItems: ["hello"], applicationActivities: nil)
    vc.popoverPresentationController?.barButtonItem = sender as? UIBarButtonItem
    self.presentViewController(vc, animated: true, completion: nil)
 }

注意这里没有If语句或其他疯狂的东西。可选的展开在iPhone上将是nil，所以行vc。popoverpresentationcontroller ?在iphone上没有任何功能。

我找到了这个解 首先，你呈现弹窗的视图控制器应该实现<UIPopoverPresentationControllerDelegate>协议。

接下来，你需要设置popoverPresentationController的委托。

添加以下功能:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
// Assuming you've hooked this all up in a Storyboard with a popover presentation style
    if ([segue.identifier isEqualToString:@"showPopover"]) {
        UINavigationController *destNav = segue.destinationViewController;
        PopoverContentsViewController *vc = destNav.viewControllers.firstObject;

        // This is the important part
        UIPopoverPresentationController *popPC = destNav.popoverPresentationController;
        popPC.delegate = self;
    }
}

- (UIModalPresentationStyle)adaptivePresentationStyleForPresentationController: (UIPresentationController *)controller {
    return UIModalPresentationNone;
}