更改appdelegate中的UILabel文本

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) UILabel *label;

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    // 初始化UILabel
    self.label = [[UILabel alloc] initWithFrame:CGRectMake(50, 50, 200, 30)];
    self.label.text = @"原始文本";
    self.label.textColor = [UIColor blackColor];
    self.label.textAlignment = NSTextAlignmentCenter;

    // 设置为window的子视图
    [self.window addSubview:self.label];
    
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}

// 在需要修改文本的地方调用下面这个方法
- (void)changeLabelText {
    self.label.text = @"新的文本";
}

@end