清除手机APP应用图标右上角的红色角标：

1.在你想要清除的地方执行以下代码

    if (@available(iOS 16.0, *)) {
        [[UNUserNotificationCenter currentNotificationCenter] setBadgeCount:0 withCompletionHandler:nil];
    }else {
        [[UIApplication sharedApplication] setApplicationIconBadgeNumber:0];
    }

2.在AppDelegate代理方法中执行以下代码(例如：- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary<UIApplicationLaunchOptionsKey,id> *)launchOptions{})

  if (@available(iOS 16.0, *)) {
        [[UNUserNotificationCenter currentNotificationCenter] setBadgeCount:0 withCompletionHandler:nil];
    }else {
        [application setApplicationIconBadgeNumber:0];
    }

API说明：

1.UNUserNotificationCenter实例方法只有16.0及以上系统版本可用

- (void)setBadgeCount:(NSInteger)newBadgeCount withCompletionHandler:(nullable void(^)(NSError *__nullable error))completionHandler API_AVAILABLE(macos(13.0), ios(16.0), tvos(16.0)) API_UNAVAILABLE(watchos);

2.setter属性变量自17.0系统版本开始废弃

@property(nonatomic) NSInteger applicationIconBadgeNumber API_DEPRECATED("Use -[UNUserNotificationCenter setBadgeCount:withCompletionHandler:] instead.", ios(2.0, 17.0));