Question

我使用以下代码进行警报视图，它可以在iPhone中使用。但是当我在iPad上运行它时会出现以下错误：

由于未捕获的异常'NSGenericException'而终止应用程序，原因是：'您的应用程序已呈现样式UIAlertControllerStyleActionSheet的UIAlertController（）。具有此样式的UIAlertController的modalPresentationStyle是UIModalPresentationPopover。您必须通过警报控制器的popoverPresentationController为此弹出窗口提供位置信息。您必须提供sourceView和sourceRect或barButtonItem。如果在显示警报控制器时不知道此信息，您可以在UIPopoverPresentationControllerDelegate方法-prepareForPopoverPresentation中提供它。'

警报视图代码如下：

let alertView = UIAlertController(title: "Select Launguage", message: "\n\n\n\n\n\n\n\n\n\n", preferredStyle: UIAlertControllerStyle.ActionSheet);

   pickerView.center.x = self.view.center.x

    alertView.view.addSubview(pickerView)

    let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil)

    alertView.addAction(action)
    presentViewController(alertView, animated: true, completion: nil)

请帮帮我。为什么它不在iPad上工作......

Answer 1

在iPad上，警报将使用UIPopoverPresentationController显示为弹出窗口，它要求您为弹出窗口的显示指定一个锚点。

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];

UIAlertController中的UIPickerView仅在iPad中出错而在iPhone中是否正确？

1 个答案: