iOS 16中UITabBar背景色/背景图不生效，UITabBarAppearance设置无效求助

可能的原因及修复步骤 #

1. 确认设置时机与对象 #

确保代码在UITabBarController的生命周期方法（如viewDidLoad）中调用，且目标对象是self.tabBar（即UITabBarController自身的tabBar属性）。如果在子ViewController中尝试设置，大概率会被UITabBarController的默认配置覆盖，无法生效。

2. 处理半透明属性干扰 #

UITabBar默认translucent属性为YES，系统会对设置的背景色做半透明处理，导致纯色显示效果不符合预期。可以强制关闭半透明：

self.tabBar.translucent = NO;

如果需要保留半透明效果，可通过backgroundEffect搭配带透明度的背景色实现：

appearance.backgroundEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleSystemMaterial];
appearance.backgroundColor = [UIColor.redColor colorWithAlphaComponent:0.8];

3. 排查全局外观设置冲突 #

如果在AppDelegate或其他全局配置中设置过UITabBar的外观，局部设置可能被覆盖。可以统一在全局配置外观：

// 在AppDelegate的application:didFinishLaunchingWithOptions:中设置
UITabBarAppearance *appearance = [UITabBarAppearance new];
appearance.backgroundColor = UIColor.redColor;
[appearance.stackedLayoutAppearance.normal setTitleTextAttributes:@{NSForegroundColorAttributeName:UIColor.redColor}];
[appearance.stackedLayoutAppearance.selected setTitleTextAttributes:@{NSForegroundColorAttributeName:UIColor.purpleColor}];

[UITabBar appearance].standardAppearance = appearance;
[UITabBar appearance].scrollEdgeAppearance = appearance;

4. 背景图设置的正确方式 #

如果需要设置背景图，不要通过backgroundColor，而是使用backgroundImage属性：

appearance.backgroundImage = [UIImage imageNamed:@"tab_bg"];
// 如需移除底部阴影线，可设置shadowImage为空
appearance.shadowImage = [UIImage new];

完整修复代码示例 #

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UITabBarAppearance *appearance = [UITabBarAppearance new];
    // 配置文字样式
    [appearance.stackedLayoutAppearance.normal setTitleTextAttributes:@{NSForegroundColorAttributeName:UIColor.redColor}];
    [appearance.stackedLayoutAppearance.selected setTitleTextAttributes:@{NSForegroundColorAttributeName:UIColor.purpleColor}];
    // 设置背景色
    appearance.backgroundColor = UIColor.redColor;
    // 关闭半透明（按需选择）
    self.tabBar.translucent = NO;
    
    self.tabBar.standardAppearance = appearance;
    self.tabBar.scrollEdgeAppearance = appearance;
}

内容的提问来源于stack exchange，提问作者aberlt