在关闭 MFMessageController 时显示 AlertView 时出错答案

【问题标题】：Error when presenting AlertView on dismissing MFMessageController在关闭 MFMessageController 时显示 AlertView 时出错
【发布时间】：2017-01-31 08:57:56
【问题描述】：

我在视图层次结构中苦苦挣扎，但我无法弄清楚这里出了什么问题。我尝试发送消息 (MFMessageComposeViewController)。我想在委托方法的帮助下根据成功（或不成功）显示alertView。取消消息时会显示 alertView 但发送消息时出现此错误：

Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior (<UIAlertController: 0x153b3c00>)

看起来好像在发送消息时（好像还有一些东西在幕后运行），在 MFMessageComposeView 被完全解除（或解除分配）之前调用了完成块，但在它被取消时却没有。如果有帮助：

- (void)messageComposeViewController:(MFMessageComposeViewController *)controller didFinishWithResult:(MessageComposeResult)result {

    int tag;

    switch (result) {
        case MessageComposeResultCancelled:
        {
            tag = 1;
            NSLog(@"Cancelled");
            break;
        }
        case MessageComposeResultFailed:
        {
            tag = 2;
            NSLog(@"Failed");
            break;
        }

        case MessageComposeResultSent:
        {
            tag = 3;
            NSLog(@"Sent");
            break;
        }
        default:
            break;
    }
    [controller dismissViewControllerAnimated:YES completion:^{
        [self alertSMSMessageWithTag:tag];
    }];
}

- (void)alertSMSMessageWithTag:(int)tag {

    UIAlertController *alertController;

    if (tag == 1) { // cancelled
        alertController = [UIAlertController alertControllerWithTitle:@"Message cancelled" message:nil preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
        [alertController addAction:ok];
    }
    if (tag == 2) { // Failed
        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Message failed" message:nil preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
        [alertController addAction:ok];
    }
    if (tag == 3) { // sent
        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Message sent" message:nil preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
        [alertController addAction:ok];
    }
    [self presentViewController:alertController animated:YES completion:nil];
}

如果有人可以帮助我...

【问题讨论】：

标签： objective-c delegates uialertview mfmessagecomposeview

【解决方案1】：

您没有以正确的方式初始化UIAlertController。您正在使用对

公开的相同变量名 alertController

if (tag == 3) {
}

但不对方法公开。而且您正在使用相同的变量名，该变量名对方法 UIAlertController *alertController; 是公开的 [self presentViewController:alertController animated:YES completion:nil]; 正在访问方法变量的公共变量，即 UIAlertController *alertController;，您已为标签 1 正确初始化。我建议您使用以下代码 -

- (void)alertSMSMessageWithTag:(int)tag {

     UIAlertController *alertController = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
    [alertController addAction:ok];
    if (tag == 1) { // cancelled
       alertController.title = @"Message cancelled";

    }
    if (tag == 2) { // Failed
        alertController.title = @"Message failed";
    }
    if (tag == 3) { // sent
       alertController.title = @"Message sent";

    }
    [self presentViewController:alertController animated:YES completion:nil];
}

希望对您有所帮助。

【讨论】：