在委托内部调用时，presentModalView 未显示

Question

我有一个名为 MainViewController 的 UIViewController （它位于 navigationController 内）。我有另一个名为 OptionsViewController 的 UIViewController。在 OptionsViewController 内部，我有一个注销按钮，单击它时，它会调用 MainViewController 中的委托： 在

- (IBAction) logout:(id)sender
{
    [self.delegate viewController:self loginSuccess:YES]; //calls this delegate

    NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
    NSString * username = [standardDefaults stringForKey:@"kApplicationUserNameKey"]; 
    NSError * error = nil;

    [standardDefaults removeObjectForKey:@"kApplicationUserNameKey"];
    [SFHFKeychainUtils deleteItemForUsername:username andServiceName:@"convore" error:&error];
    [self dismissModalViewControllerAnimated:YES];
}

MainViewController 调用的委托是：

- (void) viewController:(OptionsViewController*)viewCon loginSuccess:(BOOL)loadFlag
{
    if (loadFlag){
        LoginViewController* lvc = [[LoginViewController alloc] init];
        lvc.delegate = self;
        [self.navigationController presentModalViewController:lvc animated:YES];
          //this same code works in the viewDidLoad (it presents the LoginViewController, but not here)
        [lvc release];

        [self.groups removeAllObjects];
        [self.table reloadData];

        Topic * topic = [Topic object];
        topic.tid = [NSNumber numberWithInt:-2];
        self.detailViewController.topic = topic;
        self.detailViewController.detailItem = topic.tid;
    }
}

问题是，当调用此委托时，它应该呈现一个 LoginViewController （从上面的代码可以看出） ，但事实并非如此。我尝试将 PresentModalViewController 代码放入 MainViewController 的 viewDidLoad 内的委托中，并且它显示出来，但是当尝试在此委托中显示它时，它没有显示。这是为什么呢？是的，我检查了委托是否被调用（尝试将 NSLog 放入委托内）

更新：

OptionsViewController 显示为 modalViewController 以及 MainViewController 中的以下代码：

- (IBAction)showOptions:(id)sender
{
    if ([self.detailViewController.message isFirstResponder])
        [self.detailViewController setViewMovedUp:NO];


    OptionsViewController * opt = [[OptionsViewController alloc] init];
    opt.delegate = self;
    opt.mgvc = self;
    UINavigationController * uinc = [[UINavigationController alloc] initWithRootViewController:opt];
    uinc.navigationBar.tintColor = [UIColor blackColor];
    uinc.modalPresentationStyle = UIModalPresentationFormSheet;
    uinc.title = @"";
    uinc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;  //transition shouldn't matter
    [self presentModalViewController:opt animated:YES];

    float xCenter = 384;
    float yCenter = 512;
    if (self.splitViewController.interfaceOrientation == UIInterfaceOrientationPortrait || self.splitViewController.interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown){
        xCenter = 384;
        yCenter = 512;
    } else if (self.splitViewController.interfaceOrientation == UIInterfaceOrientationLandscapeLeft || self.splitViewController.interfaceOrientation == UIInterfaceOrientationLandscapeRight){
        xCenter = 512;
        yCenter = 384;
    }

    uinc.view.superview.frame = CGRectMake(0, 0 , 318, 209);//it's important to do this after presentModalViewController
    uinc.view.superview.center = CGPointMake(xCenter, yCenter);
    [opt release];

}

当我尝试仅显示 OptionsViewController 时本身（没有 UINavigationController，一切正常）。这是为什么呢？

Answer 1

您确定您的视图位于导航控制器内吗？如果没有，请将该行更改为：

[self presentModalViewController:lvc animated:YES];