去除UINavigationController的黑色背景

// 在需要的地方导入UINavigationBarAppearance的头文件
#import <UIKit/UIKit.h>

if (@available(iOS 13.0, *)) {
    UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc] init];
    // 设置背景颜色
    appearance.backgroundColor = [UIColor whiteColor];
    // 设置标题样式
    NSDictionary *titleTextAttributes = @{
        NSFontAttributeName: [UIFont boldSystemFontOfSize:17],
        NSForegroundColorAttributeName: [UIColor blackColor]
    };
    appearance.titleTextAttributes = titleTextAttributes;

    // 将自定义样式应用到全局的UINavigationBar
    [[UINavigationBar appearance] setStandardAppearance:appearance];
}

#import <UIKit/UIKit.h>

@interface CustomNavigationController : UIViewController

@property (nonatomic, strong) UIView *navigationBar;
@property (nonatomic, strong) UIViewController *rootViewController;

- (instancetype)initWithRootViewController:(UIViewController *)rootViewController;

@end

@implementation CustomNavigationController

- (instancetype)initWithRootViewController:(UIViewController *)rootViewController {
    self = [super init];
    if (self) {
        self.rootViewController = rootViewController;
    }
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 添加自定义的导航栏
    self.navigationBar = [[UIView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), 64)];
    self.navigationBar.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:self.navigationBar];
    
    // 添加根视图控制器
    [self addChildViewController:self.rootViewController];
    self.rootViewController.view.frame = CGRectMake(0, CGRectGetMaxY(self.navigationBar.frame), CGRectGetWidth(self.view.bounds), CGRectGetHeight(self.view.bounds) - CGRectGetHeight(self.navigationBar.frame));
    [self.view addSubview:self.rootViewController.view];
    [self.rootViewController didMoveToParentViewController:self];
}

@end

// 创建自定义导航控制器，并将需要的根视图控制器设置为其rootViewController
CustomNavigationController *customNavigationController = [[CustomNavigationController alloc] initWithRootViewController:yourRootViewController];

// 将自定义导航控制器作为根视图控制器设置给window
self.window.rootViewController = customNavigationController;