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应用程序从 Facebook 登录返回后，我在关闭模式视图时遇到问题。我遵循了 facebook 教程并对代码进行了一些自由化，因为我不想使用应用程序委托。我会发布一些代码片段

我正在使用两个类。一个类是我的初始视图，如果用户已登录，则会弹出一个名为 DayViewController 的类，然后如果用户未登录，则会弹出我的模式视图。 LoginViewController。

还应该注意的是，我正在使用故事板，并且我构建了我的应用程序，以便 DayViewController 嵌入了一个导航栏，然后嵌入到选项卡栏中。我认为我的问题出在 facebook 教程中，他们使用一些代码来获取当前显示的视图，然后将其关闭……我无法实现。

DayViewController 类——

ViewDidLoad

- (void)viewDidLoad
{
    if (FBSession.activeSession.state == FBSessionStateCreatedTokenLoaded) {
        [self openSession];
}else {
    [self showLoginView];
}
   [super viewDidLoad];
}

显示登录视图

- (void)showLoginView{

UIViewController *topViewController = [self.navigationController topViewController];
UIViewController *modalViewController = [topViewController presentedViewController];

if (![modalViewController isKindOfClass:[LoginViewController class]]) {


    LoginViewController *lvc = [self.storyboard instantiateViewControllerWithIdentifier:@"loginView"];
    [self presentViewController:lvc animated:NO completion:nil];

} else {
    LoginViewController *loginVC = [[LoginViewController alloc] init];
    [loginVC loginFailed];
}
}

sessionStateChanged

- (void)sessionStateChanged:(FBSession *)session
                  state:(FBSessionState) state
                  error:(NSError *)error
{
switch (state) {
    case FBSessionStateOpen: {

        UIViewController *topViewController =  [self.storyboard instantiateViewControllerWithIdentifier:@"loginView"];



        //LoginViewController *lvc = [self.storyboard instantiateViewControllerWithIdentifier:@"loginView"];

        if ([[topViewController presentedViewController]
             isKindOfClass:[LoginViewController class]]) {
            [self dismissViewControllerAnimated:NO completion:nil];

        }else{
        }
    }
        break;
    case FBSessionStateClosed:

    case FBSessionStateClosedLoginFailed:
        // Once the user has logged in, we want them to
        // be looking at the root view.
        //[self.navController popToRootViewControllerAnimated:NO];

        [FBSession.activeSession closeAndClearTokenInformation];

        [self showLoginView];


        break;
    default:

        break;
}

if (error) {
    UIAlertView *alertView = [[UIAlertView alloc]
                              initWithTitle:@"Error"
                              message:error.localizedDescription
                              delegate:nil
                              cancelButtonTitle:@"OK"
                              otherButtonTitles:nil];
    NSLog(@"Error");
    [alertView show];
}
}

默认 OpenSession

- (void)openSession{
[FBSession openActiveSessionWithReadPermissions:nil allowLoginUI:YES completionHandler: ^(FBSession *session,FBSessionState state, NSError *error) {
     [self sessionStateChanged:session state:state error:error];
 }];
}

LoginViewController 类---

这个类没有什么戏剧性的，只有一个登录按钮，它通过 openSession 函数抛出 facebook 状态

- (IBAction)signInButton:(id)sender {
[self.loginActivityIndicator startAnimating];
dvc = [[DayViewController alloc] init];
[dvc openSession];

//[self dismissViewControllerAnimated:YES completion:Nil];
}
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