在segue之前的MFMailComposeViewController模式视图阻止segue

Question

我在一个模式视图中使用按钮点击，这是我所能忍受的：

UIAlertView *   alert =
    [[UIAlertView alloc] initWithTitle: title
                               message: reason
                              delegate: self
                     cancelButtonTitle: @"New"
                     otherButtonTitles: @"View", nil];
    [alert show];

当在带有故事板的发送者的下面的"clickedButtonAtIndex“方法中单击”查看“按钮时，我调用了"self performSegueWithIdentifier:@"ModalSaleDetail1”iPhone :self；“

- (void) alertView: (UIAlertView *) alertView clickedButtonAtIndex: (NSInteger) buttonIndex
{
    if ([alertView.title isEqualToString: @"Successful"]) {
        switch (buttonIndex) {
            case 0:     //  New transaction
            {
                if ([self.currentSale.lastStatus isEqualToString:@"approved"]) {
                    [self displayComposerSheet];
                }
                [self clearTransaction:nil];
                break;
            }
            case 1:     //  View Transaction Details
            {
                NSLog(@"User wants to view transaction details.");
                self.currentSale.cardNumber = self.currentSale.cardNumber.bulletRedacted;
                self.cardNumberField.text = self.displayCardNumberView.text = self.currentSale.cardNumber;

                if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {  // device is iPad
                    self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:1];
                    UISplitViewController *splitVC = (UISplitViewController *)(self.tabBarController.selectedViewController);
                    UINavigationController *navC = [[splitVC viewControllers] lastObject];
                    APSaleDetailViewController *salesDVC = (APSaleDetailViewController *)navC.topViewController;
                    // If came here from new sale set to self.currentSale, otherwise do not
                    if (!salesDVC.currentSale) {
                        salesDVC.currentSale = self.currentSale;
                    }
                    salesDVC.apNewTVC = self;
                    if ([self.currentSale.lastStatus isEqualToString:@"approved"]) {
                        [self displayComposerSheet];
                    }
                } else {                                                                        // device is iPhone
                    if ([self.currentSale.lastStatus isEqualToString:@"approved"]) {
                        [self displayComposerSheet];
                    }
                    [self performSegueWithIdentifier:@"ModalSaleDetail1" sender:self];
                }
                break;
            }
            default:
            {
                NSAssert1(NO, @"Unknown alert button %d", buttonIndex);
            }
        }
    } else if .....

在我用MFMailComposeViewController实现我的电子邮件发送器之前，这个段工作得很好。

我使用以下代码来显示MFMailComposeViewController的模式视图：

// Displays an email composition interface. Populates all the Mail fields.
-(void)displayComposerSheet
{
    MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
    picker.mailComposeDelegate = self;

    [picker setSubject:@"Receipt for credit card transaction"];

    // Set up recipients
    NSArray *toRecipients = [NSArray arrayWithObject:self.currentSale.emailAddress];

    [picker setToRecipients:toRecipients];

    UIGraphicsBeginImageContext(self.view.frame.size);
    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    NSData * imageData = UIImageJPEGRepresentation(image, 1.0);

    if ( [MFMailComposeViewController canSendMail] ) {
        NSString *emailBody = @"Your credit card transaction summary and signature:";
        [picker setMessageBody:emailBody isHTML:NO];
        [picker addAttachmentData:imageData mimeType:@"image/jpeg" fileName:@"attachment"];
        NSData *myData = UIImagePNGRepresentation(self.signatureImage);
        [picker addAttachmentData:myData mimeType:@"image/png" fileName:@"Autograph"];
        [self presentModalViewController:picker animated:YES];
    }
}

现在，当self performSegueWithIdentifier:@"ModalSaleDetail1“sender:self在调用了self displayComposerSheet之后被调用时，不会发生分段。电子邮件编写器工作表显示正确，但在我发送或取消它之后，分段没有发生。如果我注释掉对self displayComposerSheet的调用，段就会正常发生(但当然没有电子邮件)。

顺便说一句，iPad代码可以很好地处理self displayComposerSheet调用，因为它不使用segues。

通常情况下，在呈现模式对话框后立即执行segue是否有效？

我正在为iOS 6.1构建Xcode4.6，并部署到iOS 5.1。我的iPhone运行5.1.1，我的iPad运行6.1。

Answer 1

• (void)performSegueWithIdentifier:(NSString *)标识符发送者：(Id)发送者NS_AVAILABLE_IOS(5_0);

您知道，此接口在iOS 5中不可用

Answer 2

我知道，这不能解决您的Segues问题，但如果您尝试返回到以前的View Controller，请尝试以下操作：

[self dismissViewControllerAnimated:YES completion:nil];