加载另一个ViewController时呈现一个模式视图控制器 [英] Presenting a modal view controller when loading another ViewController

问题描述

在用户可以使用我的应用程序之前，他必须登录.他登录后，便建立了数据库，因为我需要来自服务器的信息才能建立数据库.

Before the user can use my application he has to login. After he logged in, the database is built because I need information from the server to build it.

因此，我的根ViewController是LoginViewController，它在成功登录后以模态形式呈现实际的应用程序(navigationController堆栈).

Therefore my root ViewController is the LoginViewController which presents the actual application (a navigationController stack) modally on successful login.

如果用户已经在应用程序启动时登录(我正在使用NSUserDefaults存储凭据)，LoginViewController应该立即显示该应用程序.因此，我重写了该方法:

If the user is already logged in on application launch (I am storing the credentials with NSUserDefaults) the LoginViewController should present the application immediately. Therefore I overwrote the method:

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

    NSInteger userId = [[NSUserDefaults standardUserDefaults] integerForKey:@"selfUser"];
    if (userId != 0) {
        //[self performSelector:@selector(presentMainViewController) withObject:nil afterDelay:2];
        [self presentMainViewController];
    }
}
- (void)presentMainViewController {
    mainViewController = [[MainViewController alloc] init];
    mainViewController.managedObjectContext = managedObjectContext;
    navigationController = [[UINavigationController alloc] initWithRootViewController:mainViewController];
    navigationController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self presentModalViewController:navigationController animated:NO];
}

已执行 [self presentMainViewController]; ，但控制器未显示.如果我使用上面的行，它确实起作用.

The [self presentMainViewController]; is executed but the controller does not show up. If I use the line above it does work.

我必须在哪里放置代码以使其起作用?

Where do I have to put the code to make it work?

推荐答案

发送 viewDidAppear 时，视图堆栈可能未完全创建.因此，您应该使用 perfomSelector:withDelay 在运行循环中将调用排队.这样，您可以确保在代码运行时构建视图堆栈.

The view stack might not be completely created when viewDidAppear is send. So you should use the perfomSelector:withDelay to queue the call on the run loop. In this way you can ensure that the view stack is build when your code runs.

干杯！

这篇关于加载另一个ViewController时呈现一个模式视图控制器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！