使用TabBarController的SimpleDrillDown示例

Question

我一直在试验Apple的SimpleDrillDown示例，并尝试将其放入标签栏。问题是现在没有显示的视图，我知道App Delegate中的以下代码是导致它的。我正在努力改变它以适应tabbar并且会欣赏一些指示。

- (void)applicationDidFinishLaunching:(UIApplication *)application {

  // Create the data controller and pass it to the root view controller.
  UINavigationController *navigationController = (UINavigationController *)self.window.rootViewController;
  RootViewController *rootViewController = (RootViewController *)[[navigationController viewControllers]objectAtIndex:0];

  DataController *controller = [[DataController alloc] init];
  rootViewController.dataController = controller;
  self.dataController = controller;
}

我已将其替换为以下内容，但此行EatCatTVC *rootViewController = (RootViewController *)[[navigationController viewControllers]objectAtIndex:0];会引发错误

-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
  // Override point for customization after application launch.
  UITabBarController *tabBar = (UITabBarController *)self.window.rootViewController;
  // Create the data controller and pass it to the root view controller.

  EatCatTVC *rootViewController = (RootViewController *)[[navigationController viewControllers]objectAtIndex:0];
  DataController *controller = [[DataController alloc] init];
  rootViewController.dataController = controller;
  self.dataController = controller;
  return YES;
}

Answer 1

您的代码失败，因为您正在访问不存在的对象

EatCatTVC *rootViewController = (RootViewController *)[[navigationController viewControllers]objectAtIndex:0];

1在您的“已修改”版本中不存在navigationController。

确保“rootController”设置为UITabBarController类（我假设你在Interface Builder中设置了它）。

然后使用setViewControllers:animated:提供要存在的UITabBarController' instance with (for instance) UIViewController实例。