以编程方式设置视图

Question

我试图在 xcode 和 objective c 中不使用故事板来设置我的项目。

我的 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...

我的 viewController 文件：

.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];

}

我认为我的代码是正确的，当我运行它时我们应该有一个红屏，但我只得到一个黑屏。有人可以告诉我我是否忘记了什么，或者与项目设置有关。谢谢

Answer 1

添加

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

给你的application:didFinishLaunchingWithOptions:

Answer 2

您缺少两个步骤。

初始化window:

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

使 window 键可见：
```
[self.window makeKeyAndVisible];
```

总而言之，您的代码应如下所示：

- (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;
}

以编程方式设置视图

Setting the view programmatically

objective-c

uiviewcontroller

uiview

programmatically-created