ios - 首先显示 UIAlertController，然后显示 MFMailComposeViewController。仅在第一次工作

Question

我有 UIAlertController。单击确定，显示 MFMailComposeViewController。我通过点击电子邮件撰写屏幕中的取消按钮关闭了 MFMailComposeViewController。 MFMailComposeViewController 的委托(delegate)方法在关闭时被正确调用。 MFMailComposeViewController 成功关闭。紧接着，如果我再次尝试相同的功能(流程)。我没有得到警报，而是低于错误。可能是什么原因？我尝试了 stackoverflow 中可用的大部分解决方案。仍然遇到同样的问题。

Attempt to present <UIAlertController: 0x13890beb0> on <MFMailComposeViewController: 0x1371ef000> whose view is not in the window hierarchy!**

我正在使用 self presentViewController 来呈现 alertcontroller 和 MFMailComposeViewController。

示例代码在这里:

- (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(nullable NSError *)error{
    [controller dismissViewControllerAnimated:YES completion: nil];


}


UIAlertController * alertController=   [UIAlertController alertControllerWithTitle:@"Title" message:@"message"                    preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction* ok = [UIAlertAction
                         actionWithTitle:@"Ok"
                         style:UIAlertActionStyleDefault
                         handler:^(UIAlertAction * action)
                         {
                             [alertController dismissViewControllerAnimated:YES completion:nil];

                             MFMailComposeViewController *mailComposerVC = [MFMailComposeViewController new];

                             mailComposerVC.mailComposeDelegate = self;

                             if ([MFMailComposeViewController canSendMail]) {


                                 [self presentViewController:(MFMailComposeViewController*)mailComposerVC animated: true completion: nil];
                             }

                         }];
    UIAlertAction* cancel = [UIAlertAction
                             actionWithTitle:@"Cancel"
                             style:UIAlertActionStyleDefault
                             handler:^(UIAlertAction * action)
                             {
                                 [alertController dismissViewControllerAnimated:YES completion:nil];

                             }];

    [alertController addAction:ok];
    [alertController addAction:cancel];

    [self presentViewController:alertController animated:false completion:nil];

Answer 1

请使用以下代码来显示邮件 Controller :

UIAlertController * alertController=   [UIAlertController alertControllerWithTitle:@"Title" message:@"message"                    preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction* ok = [UIAlertAction  actionWithTitle:@"Ok"  style:UIAlertActionStyleDefault  handler:^(UIAlertAction * action) {
                         [alertController dismissViewControllerAnimated:YES completion:nil];

                         MFMailComposeViewController *composer = [[MFMailComposeViewController alloc] init];

                         mailComposerVC.mailComposeDelegate = self;

                         if ([MFMailComposeViewController canSendMail]) {

                            [[[[[UIApplication sharedApplication] delegate] window] rootViewController] presentViewController:mailComposerVC
                                                                                             animated:YES
                                                                                           completion:nil];

                         }

                     }];
UIAlertAction* cancel = [UIAlertAction actionWithTitle:@"Cancel"  style:UIAlertActionStyleDefault  handler:^(UIAlertAction * action)  {
                             [alertController dismissViewControllerAnimated:YES completion:nil];

                         }];

[alertController addAction:ok];
[alertController addAction:cancel];

[self presentViewController:alertController animated:false completion:nil];