在关闭MFMessageController时显示AlertView时出错

Question

我正在为视图层次结构而苦苦挣扎，但我不知道这里出了什么问题。我尝试发送一条消息(MFMessageComposeViewController)。我想展示一个依赖于委托方法的成功(或失败)的alertView。取消消息时会显示alertView，但发送消息时会出现以下错误：

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(好像仍有一些东西在幕后运行)，完成块在MFMessageComposeView完成之前被调用，而不是在消息被取消时调用。如果它能帮上忙：

- (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];
}

如果有人能帮我..。

Answer 1

您没有以正确的方式初始化UIAlertController。您正在使用相同的变量名alertController，该名称对

if (tag == 3) {
}

但不是对该方法公开的。并且您使用的变量名对方法是公共的，[self presentViewController:alertController animated:YES completion:nil];正在访问方法变量的公共变量，即UIAlertController *alertController;，您已为标记1正确初始化了该变量。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];
}

希望能对你有所帮助。