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

Question

我是iOS开发中的新手，试图学习如何以编程方式创建和设置视图。

我想在Obj-C中做快速陈述

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

项目：单一视图应用程序。尝试链接默认的Created ViewController.h

根据Krunals答案我更新了代码，但导航控制器未在模拟器中显示

Cmd +单击控制器不会导航到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（用作导航的根控制器）导航控制器堆栈之前初始化视图控制器ViewController。

以下是初始化简单视图控制器的示例代码

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

以下是使用storyboard初始化的示例代码

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

以下是使用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，请仅尝试此代码（从您的应用代理发布中删除其他代码）：

// 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
}

Answer 2

感谢Krunal的详细解答。

感谢dan支持

我发现问题而不是self.window.rootViewController，我输入了window.rootViewController。

设置self.window.rootViewController解决了问题。

我不知道self.window.rootViewController和window.rootViewController之间的区别以及问题的原因。

如果有人知道答案，请提供评论答案

#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

在您执行此操作之前，删除文件Main.storyboard并让Main interface选项为空。

并添加此代码：

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：如果您想将故事板与UINavigationController一起使用，请尝试以下操作：

Answer 4

添加UIViewController并添加UINavigationController

      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];
            }