ios - 如何将 tabBarController 设置为 rootViewController

Question

在 AppDelegate 中，我想将 TabBarController 设置为 rootViewController。

我试过了:

UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;

我也试过:

UITabBarController *tabBarController = [[UITabBarController alloc] init];
self.window.rootViewController = tabBarController;

但它说:

Failed to instantiate the default view controller for UIMainStoryboardFile 'Main' - perhaps the designated entry point is not set?

我在 AppDelegate 中的完整代码:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;

    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

    // Movies
    MediaListViewController *moviesVC = (MediaListViewController *)[storyboard instantiateViewControllerWithIdentifier:@"MediaList"];
    moviesVC.title = @"Movies";
    moviesVC.tabBarItem.image = [[UIImage imageNamed:@"superman"] imageWithRenderingMode:(UIImageRenderingModeAlwaysTemplate)];
    UINavigationController *moviesNC = [[UINavigationController alloc] initWithRootViewController:moviesVC];
    moviesNC.navigationBar.barTintColor = [[UIColor blackColor]colorWithAlphaComponent:0.5];
    moviesNC.navigationBar.tintColor = [UIColor yellowColor];
    moviesNC.navigationBar.barStyle = UIBarStyleBlack;

    //DVDs
    MediaListViewController *dvdsVC = (MediaListViewController *)[storyboard instantiateViewControllerWithIdentifier:@"MediaList"];
    dvdsVC.title = @"DVDs";
    dvdsVC.tabBarItem.image = [[UIImage imageNamed:@"hulk"] imageWithRenderingMode:(UIImageRenderingModeAlwaysTemplate)];
    UINavigationController *dvdsNC = [[UINavigationController alloc] initWithRootViewController:dvdsVC];
    dvdsNC.navigationBar.barTintColor = [[UIColor blackColor]colorWithAlphaComponent:0.5];
    dvdsNC.navigationBar.tintColor = [UIColor yellowColor];
    dvdsNC.navigationBar.barStyle = UIBarStyleBlack;

    tabBarController.viewControllers = @[moviesNC, dvdsNC];
    tabBarController.tabBar.barTintColor = [[UIColor blackColor]colorWithAlphaComponent:0.5];
    [self.window makeKeyAndVisible];

    return YES;
}

Answer 1

info.plist 中有一个键，它指定需要在您的应用程序中使用的主 Storyboard文件。



因此，每当您的应用程序加载时，iOS 都会检查此键并尝试使用与此键的值匹配的名称来初始化 Storyboard 。为了初始化 Storyboard，应该设置一个入口点(初始 View Controller )。即使您通过代码设置选项卡 Controller ，iOS 系统也会尝试初始化 Storyboard 并抛出该消息。

因此，要解决此问题，有两种选择:

只需在您的 Storyboard文件中设置一个初始 View Controller (一个虚拟入口点)，在应用程序委托(delegate)中您可以覆盖它(我推荐这种方法)

继续删除UIMainStoryboardFile又名主要 storyboard file base name来自 info.plist 的 key (这种方法简单且有效，但除非设置入口点，否则永远无法初始化 Storyboard 。因此，如果您选择此选项，则不能永远使用 Storyboard 进行设计，您只能使用 xib 或通过代码)