[UINavigationControllerselectedIndex]：發送到UITabBarController實體的無法識別的選擇器-有解無憂

從一個螢屏導航到另一個螢屏（TabBarController 的實體/子螢屏）時，應用程式崩潰并拋出錯誤。

執行緒 1：“-[UINavigationController selectedIndex]：無法識別的選擇器發送到實體 0x105870800”

 UINavigationController *nav_1 = [UIApplication sharedApplication].keyWindow.rootViewController;
    
 UITabBarController *tab = (TabbarController*)[UIApplication sharedApplication].keyWindow.rootViewController;
 NSInteger sel_idx =  tab.selectedIndex; //App Crashing here with error:- Thread 1: "-[UINavigationController selectedIndex]: unrecognized selector sent to instance 0x105870800"
 UINavigationController *nav = [tab.viewControllers objectAtIndex:sel_idx];

在使用以下代碼進行螢屏重定向但遇到錯誤之前它作業正常Multiple Navigation Stack，這導致了不必要的崩潰和應用程式凍結問題

 if ((UserDefaults.standard.value(forKey: "isUserSignIn") as? Bool) == true)
 {
     NSLog("if called tabBarController")
     self.window?.rootViewController = storyBoard.instantiateViewController(withIdentifier: "tabBarController")
 } 
 else
 {
    self.window?.rootViewController = storyBoard.instantiateViewController(withIdentifier: "ProfileNavController")                                                          
 }

現在我已經更改了如下代碼，bcz 我正面臨Multiple Navigation Stack. 因此，更改為以下代碼后，Multiple Navigation Stack問題已解決，但面臨提到的錯誤

if ((UserDefaults.standard.value(forKey: "isUserSignIn") as? Bool) == true)
{
   NSLog("if called tabBarController")
   let tabBar = storyBoard.instantiateViewController(withIdentifier: "tabBarController")
   nav = UINavigationController(rootViewController: tabBar)
   self.window?.rootViewController = nav
} 
else
{
               
  NSLog("else called LoginViewController")                    
  let login = storyBoard.instantiateViewController(withIdentifier: "LoginViewController")
  nav = UINavigationController(rootViewController: login)
  self.window?.rootViewController = nav
                                       
}

因錯誤而崩潰

[UINavigationController selectedIndex]：發送到 UITabBarController 實體的無法識別的選擇器

uj5u.com熱心網友回復：

要在將根更改為您需要的導航后訪問選項卡

 UINavigationController *nav_1 = [UIApplication sharedApplication].keyWindow.rootViewController;
 UITabBarController *tab = [nav_1.viewControllers objectAtIndex:0]

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標籤：IOS 目标-c 导航控制器 uitabbar控制器

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