ios - 如何在 Objective C 中以编程方式设置 Root View Controller ？

Question

我是 iOS 开发的新手，正在尝试学习如何以编程方式创建和设置 View 。

我正在尝试在 Obj-C 中做快速声明

window?.rootViewController = UINavigationController(rootViewController : ViewController()) 

项目:单 View 应用程序。尝试链接默认创建的 ViewController.h

根据 Krunals Answer，我更新了代码，但模拟器中未显示导航 Controller

Cmd+Click Controller 不会导航到 ViewController 文件

#import "AppDelegate.h"
#import "ViewController.h"

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
UIScreen *screen=[[UIScreen alloc]init];
    UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    self.window.makeKeyAndVisible;




    ViewController *controller = [[ViewController alloc] init];



    window.rootViewController = [[UINavigationController alloc] initWithRootViewController:controller] ;

Answer 1

在添加(用作导航的根 Controller )到导航 Controller 堆栈之前，初始化您的 View Controller ViewController。

这里是初始化简单 View Controller 的示例代码

UIViewController *controller = [[UIViewController alloc] init];

这是使用 Storyboard初始化的示例代码

ViewController *controller = [[UIStoryboard storyboardWithName:@"Main" bundle:nil] instantiateViewControllerWithIdentifier:@"<ViewController - string identifier of your view controller>"];

这是使用 NIB/Bundle 初始化的示例代码

ViewController *controller = [[ViewController alloc] initWithNibName:@"<ViewController - string NIB name>>" bundle:nil];

根据您的代码和以下评论，仅尝试此代码(从您的应用程序委托(delegate)启动中删除其他代码):

// make sure your NIB name is 'ViewController' 

ViewController *controller = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
if (controller != nil) {
    self.window.rootViewController = [[UINavigationController alloc] initWithRootViewController: controller];
    self.window.makeKeyAndVisible;
} else {
   //print - your view controller is nil
}