在自定义设置导航背景色时，使用下面的方法，在iOS15+系统上不起作用：

UINavigationBar *appearance = [UINavigationBar appearance];
//        [appearance confi];
        [appearance setBarTintColor:[UIColor whiteColor]];
        [appearance setTintColor: [UIColor whiteColor]];
        appearance.translucent = NO;
        NSMutableDictionary *textAttribute = [NSMutableDictionary dictionary];
        textAttribute[NSForegroundColorAttributeName] = MPColorBlue;//标题颜色
        textAttribute[NSFontAttributeName] = [UIFont boldSystemFontOfSize:18];//标题大小
        [appearance setTitleTextAttributes:textAttribute];
        
        UIColor *color = MPMainColor;
        UIImage *backGroundImage = [UIImage imageWithColor:color];
        backGroundImage = [backGroundImage resizableImageWithCapInsets:UIEdgeInsetsZero resizingMode:UIImageResizingModeStretch];
        [appearance setBackgroundImage:backGroundImage forBarMetrics:UIBarMetricsDefault];
//        appearance.backgroundColor = color;
    
        //去除底部黑线
        [appearance setShadowImage:[UIImage new]];

但是，如你的页面有scrollView，例如table、webView这些，滑动的时候，导航颜色会变为你设置的颜色，但是一旦滑动到顶部，导航又会不正常，变成黑色；

查了资料，说在iOS15+使用下面的方法：

UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc] init];
    
    [appearance configureWithOpaqueBackground];
    NSMutableDictionary *textAttribute = [NSMutableDictionary dictionary];
    textAttribute[NSForegroundColorAttributeName] = MPColorBlue;//标题颜色
    textAttribute[NSFontAttributeName] = [UIFont boldSystemFontOfSize:18];//标题大小
    [appearance setTitleTextAttributes:textAttribute];
    
    //去除底部黑线
    [appearance setShadowImage:[UIImage new]];
    
    UIColor *color = MPMainColor;
     appearance.backgroundColor = color;
    
    self.navigationBar.standardAppearance = appearance;

该方法表现和上面一致；

最终在一个文章里看到这个属性：

self.navigationBar.scrollEdgeAppearance

需要把这个也设置了才会表现正常，最终完整的设置如下：

UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc] init];
    
    [appearance configureWithOpaqueBackground];
    NSMutableDictionary *textAttribute = [NSMutableDictionary dictionary];
    textAttribute[NSForegroundColorAttributeName] = MPColorBlue;//标题颜色
    textAttribute[NSFontAttributeName] = [UIFont boldSystemFontOfSize:18];//标题大小
    [appearance setTitleTextAttributes:textAttribute];
    
    //去除底部黑线
    [appearance setShadowImage:[UIImage new]];
    
    UIColor *color = MPMainColor;
    appearance.backgroundColor = color;
    
    self.navigationBar.standardAppearance = appearance;
    self.navigationBar.scrollEdgeAppearance = appearance;

我这里设置的 backgroundColor，你也可以设置BackgroundImage