如何在 Objective C 中以編程方式設置根視圖控制器？

Question

我是 iOS 開發的新手，試圖學習如何以編程方式創建和設置視圖。

我正在嘗試在 Obj-C 中快速聲明

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

項目：單視圖應用程序。 嘗試鏈接默認創建的 ViewController.h

根據 Krunals 的回答，我更新了代碼，但模擬器中未顯示導航控制器

Cmd+單擊控制器不會導航到 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（用作導航的根控制器）到導航控制器堆棧之前初始化您的視圖控制器ViewController 。

這是初始化簡單視圖控制器的示例代碼

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

這是使用故事板初始化的示例代碼

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

這是使用 NIB/Bundle 初始化的示例代碼

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

根據您的代碼和以下評論，僅嘗試使用此代碼（從您的應用程序委托啟動中刪除其他代碼）：

// 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
}

Answer 2

感謝 Krunal 的詳細回答。

感謝 dan 的支持

我發現問題而不是 self.window.rootViewController ，我輸入了 window.rootViewController 。

設置 self.window.rootViewController 解決了問題。

我不知道 self.window.rootViewController 和 window.rootViewController 之間的區別以及問題的原因。

如果有人知道答案，請在評論中提供答案

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


@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    UIScreen *screen=[[UIScreen alloc]init];
    UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];


    self.window.makeKeyAndVisible;




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





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

Answer 3

刪除文件Main.storyboard並在執行此操作之前讓Main interface選項為空。

並添加以下代碼：

self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor whiteColor];
ViewController *vc = [[ViewController alloc] init];
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
self.window.rootViewController = nav;
[self.window makeKeyAndVisible];

更新：如果您想將故事板與UINavigationController一起使用，請嘗試以下操作：

Answer 4

添加 UIViewController 並使用 UINavigationController 添加

      UIStoryboard *storyboard = self.window.rootViewController.storyboard;
           UIViewController *rootViewController= [storyboard instantiateViewControllerWithIdentifier:kIdentifier];
            [self setRootViewController:rootViewController];


        #pragma mark - Set RootView Controller
        -(void)setRootViewController:(UIViewController *)rootViewController {
            self.window.rootViewController = rootViewController;
            [self.window makeKeyAndVisible];
        }


         UIStoryboard *storyboard = self.window.rootViewController.storyboard;
           UIViewController *rootViewController= [storyboard instantiateViewControllerWithIdentifier:kIdentifier];

UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
    [self setRootViewController:navController];

-(void)setRootViewController:(UINavigationController *)rootViewController {
                self.window.rootViewController = rootViewController;
                [self.window makeKeyAndVisible];
            }