Setting the view programmatically

Question

I am trying to set my project without using storyboards in xcode and with objective c.

My appDelegate:

.h

#import <UIKit/UIKit.h>

#import "ViewController.h"



@interface AppDelegate : UIResponder <UIApplicationDelegate>



@property (strong, nonatomic) UIWindow *window;



@end

.m

#import "AppDelegate.h"



@interface AppDelegate ()



@end



@implementation AppDelegate





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

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

    self.window.rootViewController = vc;

    return YES;

}



etc...

My viewController file:

.m

#import "ViewController.h"



@interface ViewController ()



@end



@implementation ViewController



- (void)viewDidLoad {

    [super viewDidLoad];



    UIView *view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    view.backgroundColor = [UIColor redColor];

    [self.view addSubview:view];



}

I think my code is right and we should have a red screen when I run it, but I only get a black screen. Can someone tell me if I have forgotten something or is it something to do with the project settings. Thanks.

Answer 1

You are missing two steps.

Initialize the window:

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

Make the window key & visible:
```
[self.window makeKeyAndVisible];
```

So all together, your code should look like this:

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

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

    // Add the view controller to the window
    ViewController *vc = [[ViewController alloc] init];
    self.window.rootViewController = vc;

    // Make window key & visible
    [self.window makeKeyAndVisible];

    return YES;
}

Setting the view programmatically

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