View Controller不在App Delegate中顯示

Question

我正在嘗試加載沒有登錄帳戶的viewController，但是它給了我這個錯誤Warning: Attempt to present <DefaultViewController: 0xb96cac0> on <MainViewController: 0xb95c320> whose view is not in the window hierarchy! 這是我現在正在使用的代碼：

BOOL returnAllOff = [[User data] returnAllOff];

if (returnAllOff) {
    DefaultViewController *viewController =[[DefaultViewController alloc]
    init];
    UIViewController *presentingController = [[[[UIApplication sharedApplication] delegate] window] rootViewController];
    [presentingController presentViewController:viewController animated:YES completion:nil];

}

Answer 1

實際上，這是從AppDelegate加載ViewController的正確方法。

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    DefaultViewController *viewController = [[DefaultViewController alloc] initWithNibName:@"DefaultViewController" bundle:nil];
    self.window.rootViewController = viewController;
    [self.window makeKeyAndVisible];

Answer 2

通過在appDElegate中導入DefaultViewController來嘗試這一操作。

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
DefaultViewController *viewController = [[DefaultViewController alloc] init];
self.window.rootViewController = viewController;
[self.window makeKeyAndVisible];