ios - 使用 TabBarController 的 SimpleDrillDown 示例

Question

我一直在尝试 Apple 的 SimpleDrillDown 示例，并尝试将其放入选项卡栏中。问题是 View 现在不显示，我知道是应用程序委托(delegate)中的以下代码导致了它。我正在努力更改它以适应选项卡栏，并且希望得到一些指示。

- (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]; 抛出错误

-(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];

这一行navigationController在您的“修改”版本中不存在。

确保“rootController”设置为UITabBarController类(我假设您确实在Interface Builder中设置了它)。

然后使用 setViewControllers:animated: 为 UITabBarController' 实例提供(例如)UIViewController` 实例。