iOS15系統下強制了對navigationBar統一的樣式管理，在應用打開的時候需要進行樣式的默認設置，這樣統一設置后每個導航器的背景、分割線都會變成統一的樣式，如下。

if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance *app = [UINavigationBarAppearance new];
        [app configureWithDefaultBackground];
        
        app.backgroundColor = UIColor.whiteColor;
        app.backgroundImage = [UIImage bt_imageWithColor:UIColor.redColor equalSize:100];
        app.shadowColor = UIColor.yellowColor;
        
        [UINavigationBar appearance].scrollEdgeAppearance = app;
        [UINavigationBar appearance].standardAppearance = app;
    }

這里的standardAppearance為其它Appearance屬性的默認值，不設置的話在有UIScrollView的界面進行滑動的時候導航器樣式會改變。其它Appearance源碼如下：

///  When set and this item is topmost, overrides the hosting navigation bar's standardAppearance. See UINavigationBar.standardAppearance for further details.
@property (nonatomic, readwrite, copy, nullable) UINavigationBarAppearance *standardAppearance API_AVAILABLE(ios(13.0), tvos(13.0));
///  When set and this item is topmost, overrides the hosting navigation bar's compactAppearance. See UINavigationBar.compactAppearance for further details.
@property (nonatomic, readwrite, copy, nullable) UINavigationBarAppearance *compactAppearance API_AVAILABLE(ios(13.0));
///  When set and this item is topmost, overrides the hosting navigation bar's scrollEdgeAppearance. See UINavigationBar.scrollEdgeAppearance for further details.
@property (nonatomic, readwrite, copy, nullable) UINavigationBarAppearance *scrollEdgeAppearance API_AVAILABLE(ios(13.0));
///  When set and this item is topmost, overrides the hosting navigation bar's compactScrollEdgeAppearance. See UINavigationBar.h for further details.
@property (nonatomic, readwrite, copy, nullable) UINavigationBarAppearance *compactScrollEdgeAppearance API_AVAILABLE(ios(15.0));

導航器個別樣式的設置方法總結

這個時候如果有一個VC需要將分割線隱藏，或者設置分割線的顏色用以前的方法會失效，這里總結一些導航器個別樣式常用的設置方法。

隱藏分割線

if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance * app = self.navigationItem.standardAppearance;
        if (app == nil) {
            app = [UINavigationBar.appearance.standardAppearance copy];
        }
        app.shadowColor = UIColor.clearColor;
        self.navigationItem.scrollEdgeAppearance = app;
        self.navigationItem.standardAppearance = app;
        return;
    }
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];

設置分割線顏色,iOS15分割線高度不能設置

 if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance * app = self.navigationItem.standardAppearance;
        if (app == nil) {
            app = [UINavigationBar.appearance.standardAppearance copy];
        }
        app.shadowColor = color;
        self.navigationItem.scrollEdgeAppearance = app;
        self.navigationItem.standardAppearance = app;
        return;
    }
    [self.navigationController.navigationBar setShadowImage:[UIImage bt_imageWithColor:color size:CGSizeMake(BTUtils.SCREEN_W, height)]];

設置導航器背景圖片

if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance * app = self.navigationItem.standardAppearance;
        if (app == nil) {
            app = [UINavigationBar.appearance.standardAppearance copy];
        }
        [app configureWithDefaultBackground];
        app.backgroundImage = bgImg;
        self.navigationItem.scrollEdgeAppearance = app;
        self.navigationItem.standardAppearance = app;
        return;
    }
    
    
    self.navigationController.navigationBar.translucent = NO;
    [self.navigationController.navigationBar setBackgroundImage:bgImg forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    [self.navigationController.navigationBar setClipsToBounds:NO];

設置導航器背景顏色

   if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance * app = self.navigationItem.standardAppearance;
        if (app == nil) {
            app = [UINavigationBar.appearance.standardAppearance copy];
        }
        [app configureWithDefaultBackground];
        app.backgroundImage = [UIImage bt_imageWithColor:color size:CGSizeMake(BTUtils.SCREEN_W, BTUtils.NAV_HEIGHT)];
        app.backgroundColor = color;
        self.navigationItem.scrollEdgeAppearance = app;
        self.navigationItem.standardAppearance = app;
        return;
    }
    self.navigationController.navigationBar.translucent = NO;
    [self.navigationController.navigationBar setBackgroundImage:[UIImage bt_imageWithColor:color] forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    [self.navigationController.navigationBar setClipsToBounds:NO];
    self.navigationController.navigationBar.backgroundColor=color;

設置導航器透明

    if (@available(iOS 15.0, *)) {
        UINavigationBarAppearance * app = self.navigationItem.standardAppearance;
        if (app == nil) {
            app = [UINavigationBar.appearance.standardAppearance copy];
        }
        [app configureWithTransparentBackground];
        app.backgroundImage = [UIImage bt_imageWithColor:UIColor.clearColor size:CGSizeMake(BTUtils.SCREEN_W, BTUtils.NAV_HEIGHT)];
        app.backgroundColor = UIColor.clearColor;
        self.navigationItem.scrollEdgeAppearance = app;
        self.navigationItem.standardAppearance = app;
        self.navigationController.navigationBar.translucent = YES;
        return;
    }
    self.navigationController.navigationBar.translucent = YES;
    [self.navigationController.navigationBar setBackgroundImage:[UIImage bt_imageWithColor:UIColor.clearColor] forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
    [self.navigationController.navigationBar setClipsToBounds:YES];
    self.navigationController.navigationBar.backgroundColor=UIColor.clearColor;