Xcode 13 HelloWorld App Black Screen - ObjectiveC [duplicate]

Question

I'm using Xcode 13, tried to taste the function of using pure Objective-c code to set up my HelloWorld App, but run into Black Screen. Any kind thoughts? Bellow is that I've done.

1 - New Project, select App, Interface - Storyboard, Language - Objective-C, Create. 2 - Remove viewController.h, viewController.m, Main storyboard xib.to trash. 3 - Create Cocoa Touch Class - RootViewController, UN-select Also create XIB File.

Then modified files are looks below:

//
//  AppDelegate.h
//  HelloCode
//
//  Created by Herman Ye on 2022/2/26.
//

#import <UIKit/UIKit.h>
#import "RootViewController.h"

@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;

@end

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate


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

    self.window.backgroundColor = [UIColor whiteColor];
    //self.window.rootViewController = [[RootViewController alloc] init];
    self.window.rootViewController = RootViewController.new;
    [self.window makeKeyAndVisible];

    return YES;
}

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    [self renderPage];
}

-(void) renderPage {
    CGRect screen = [[UIScreen mainScreen] bounds];
    CGFloat labelWidth = 90;
    CGFloat labelHeight = 20;
    CGFloat labelTopView = 150;
    CGRect frame = CGRectMake((screen.size.width - labelWidth)/2, labelTopView, labelWidth, labelHeight);
    UILabel* label = [[UILabel alloc] initWithFrame:frame];
    
    label.text = @"Hello Code";
    
    label.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:label];
}
... ...

PS added log into SceneDelegate

//
//  SceneDelegate.m
//  HelloWorld
//
//  Created by Herman Ye on 2022/2/24.
//

#import "SceneDelegate.h"

@interface SceneDelegate ()

@end

@implementation SceneDelegate


- (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions {
    // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
    // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
    // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
    NSLog(@"%@", @"SceneDelegate1=============================>willConnectToSession");
}


- (void)sceneDidDisconnect:(UIScene *)scene {
    // Called as the scene is being released by the system.
    // This occurs shortly after the scene enters the background, or when its session is discarded.
    // Release any resources associated with this scene that can be re-created the next time the scene connects.
    // The scene may re-connect later, as its session was not necessarily discarded (see `application:didDiscardSceneSessions` instead).
    NSLog(@"%@", @"SceneDelegate2=============================>sceneDidDisconnect");
}


- (void)sceneDidBecomeActive:(UIScene *)scene {
    // Called when the scene has moved from an inactive state to an active state.
    // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    NSLog(@"%@", @"SceneDelegate3=============================>sceneDidBecomeActive");
}


- (void)sceneWillResignActive:(UIScene *)scene {
    // Called when the scene will move from an active state to an inactive state.
    // This may occur due to temporary interruptions (ex. an incoming phone call).
    NSLog(@"%@", @"SceneDelegate4=============================>sceneWillResignActive");
}


- (void)sceneWillEnterForeground:(UIScene *)scene {
    // Called as the scene transitions from the background to the foreground.
    // Use this method to undo the changes made on entering the background.
    NSLog(@"%@", @"SceneDelegate5=============================>sceneWillEnterForeground");
}


- (void)sceneDidEnterBackground:(UIScene *)scene {
    // Called as the scene transitions from the foreground to the background.
    // Use this method to save data, release shared resources, and store enough scene-specific state information
    // to restore the scene back to its current state.
    NSLog(@"%@", @"SceneDelegate6=============================>sceneDidEnterBackground");
}


@end

Run app log: 2022-02-27 10:32:14.811892+0800 HelloCode[29356:4206590] SceneDelegate1=============================>willConnectToSession 2022-02-27 10:32:14.812183+0800 HelloCode[29356:4206590] SceneDelegate5=============================>sceneWillEnterForeground 2022-02-27 10:32:14.814368+0800 HelloCode[29356:4206590] SceneDelegate3=============================>sceneDidBecomeActive

Answer 1

The Black Screen disappeared - issue solved by making the change like below. But I do NOT quite understand the difference/reason, any kind explanation is highly appreciated for new bird like me :-)

Original code(black screen displayed) in SceneDelegate.m

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    RootViewController *rootViewController  = RootViewController.new;
    rootViewController.view.backgroundColor = UIColor.greenColor;
    self.window.rootViewController = rootViewController;
    [self.window makeKeyAndVisible];

Current code(page is properly rendered) in SceneDelegate.m

    UIWindowScene *windowScene = (UIWindowScene *)scene;
    self.window = [[UIWindow alloc] initWithWindowScene:windowScene];
    self.window.frame = windowScene.coordinateSpace.bounds;

    RootViewController *rootViewController  = RootViewController.new;
    rootViewController.view.backgroundColor = UIColor.greenColor;
    self.window.rootViewController = rootViewController;
    [self.window makeKeyAndVisible];