其视图不在窗口层次结构中 - 电子邮件表单 [英] whose view is not in the window hierarchy - email form

问题描述

我在 appdelegate 中从 viewcontroller 调用一个方法.当我测试功能时，我只使用了 NSLog 消息，它工作正常(因此 viewcontroller 和 appdelegate 之间的连接是可以的).一旦我将电子邮件表单添加到此方法中，问题就会出现.我收到的消息是:

I'm calling a method from viewcontroller in an appdelegate. When I was testing functionality I just used NSLog message which works fine (so the connection between viewcontroller and appdelegate is OK). The problem appears once I add a email form into this method. The message I receive is:

Warning: Attempt to present <MFMailComposeViewController: 0x1fdc3990> on <ViewController: 0x1fd9e3b0> whose view is not in the window hierarchy!

谁知道该怎么做?我知道有很多主题涉及其视图不在窗口层次结构中"的问题，但没有一个对我有帮助.

Anyone who know what to do? I know there are lot of topics with 'whose view is not in the window hierarchy' issue but none of them helped me.

ViewController.m

ViewController.m

...
-(void)mail{
    NSLog(@"blablabla");
    if ([MFMailComposeViewController canSendMail]) {

        MFMailComposeViewController *mail = [[MFMailComposeViewController alloc] init];
        mail.mailComposeDelegate = self;

        [mail setSubject:@"Hello and welcome!"];

        NSArray *toRecipients = [NSArray arrayWithObject:@"[e-mail]"];
        [mail setToRecipients:toRecipients];
        [mail setCcRecipients:toRecipients];

        NSString *emailBody = @"Hey all!";
        [mail setMessageBody:emailBody isHTML:NO];

        mail.modalPresentationStyle = UIModalPresentationPageSheet;
        [self presentViewController:mail animated:YES completion:nil];


    } else {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error!"
                                                        message:@"E-mail is not supported on your device"
                                                       delegate:nil
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        [alert show];
    }
}

-(void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error{

    switch (result) {
        case MFMailComposeResultCancelled:
            break;
        case MFMailComposeResultSaved:
            NSLog(@"mail saved");
            break;
        case MFMailComposeResultSent:
            NSLog(@"mail sent");
            break;
        case MFMailComposeResultFailed:
            NSLog(@"mail failed");
            break;
    }
    [self dismissViewControllerAnimated:YES
                             completion:nil];
}
...

Appdelegate.m

Appdelegate.m

...
-(void)something {
     ViewController * vc = [[ViewController alloc] init];
     [vc mail];
}
...

这就是解决我的问题的方法:

This is what solved my problem:

- (void)something {
    ViewController *rootViewController = (ViewController*)self.window.rootViewController;
    [rootViewController mail];
}

另请查看 rmaddy 的答案以获取更多信息.

Also check the answer by rmaddy for more info.

推荐答案

既然您已经发布了代码，问题就很明显了.您创建了一个视图控制器，但从未显示它(在 something 方法中).然后你在这个未显示的视图控制器 (mail) 上调用一个方法，它试图从未显示的视图控制器显示邮件视图控制器.这就是导致错误的原因.

Now that you've posted code, the problem is obvious. You create a view controller but you never display it (in the something method). Then you call a method on this undisplayed view controller (mail) which attempts to display the mail view controller from the undisplayed view controller. This is what causes the error.

您需要从已经显示的视图控制器中显示邮件控制器(例如 rootViewController 可能).

You need to display the mail controller from a view controller that is already being displayed (such as the rootViewController maybe).

你的 ViewController 类的重点是什么?

What is the point of your ViewController class?

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