演示正在进行时在场吗？尝试在 facebook 登录后使用解析显示新视图。

我试图呈现一个我已经为用户输入数据并保存在解析中的 UITableView。我很确定我没有呈现导航视图。

当我登录时，我收到错误：

Checklists[4516:c07] Warning: Attempt to present <ChecklistsViewController: 0x10525e90> 
on <UINavigationController: 0x9648270> while a presentation is in progress!

感谢您的帮助。

#import "LoginViewController.h"
#import "ChecklistsViewController.h"
#import "SetupViewController.h"
#import <Parse/Parse.h>

@interface LoginViewController ()

@end

@implementation LoginViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    PFLogInViewController *login = [[PFLogInViewController alloc] init];
    login.fields = PFLogInFieldsFacebook;
    // Need to set the delegate to be this controller.
    login.delegate = self;
    login.signUpController.delegate = self; //signUpController is a property on the login view controller
    [self presentModalViewController:login animated:NO];

}

    - (void)logInViewController:(PFLogInViewController *)logInController didLogInUser:(PFUser *)user
{
    [self dismissModalViewControllerAnimated:YES];
    NSLog(@"Successfully logged in.");
    ChecklistsViewController *controller = [[ChecklistsViewController alloc] initWithStyle:UITableViewStylePlain];
    controller.modalTransitionStyle = UITableViewStylePlain;
    [self presentModalViewController:controller animated:YES];

}

此方法已被弃用一段时间了

     presentModalViewController:animated:

你应该用这个代替

    presentViewController:animated:completion:

这同样适用

    dismissModalViewControllerAnimated:

现在我们用这个

    dismissViewControllerAnimated:completion:

当我们不需要完成块时，我们只需将其设置为 nil 即可。

但就您而言，完成块可以解决您的问题...它确保事件的正确顺序，即在解散完成之前不会发生演示。

    - (void)logInViewController:(PFLogInViewController *)logInController 
                   didLogInUser:(PFUser *)user
{
    [self dismissViewControllerAnimated:YES completion:^{
        NSLog(@"Successfully logged in.");
        ChecklistsViewController *controller = 
              [[ChecklistsViewController alloc] initWithStyle:UITableViewStylePlain];
        controller.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
        [self presentViewController:controller animated:YES completion:nil];
    }];

}

[注意 - modalTransitionStyle 在您的原始代码中不正确，我也更改了它。谢谢Daniel G指出这一点]