iOS TabBarController：在進入新標籤之前運行檢查

Question

我有一個包含UITabBarController的應用程序。只有滿足條件時才應該輸入最後一個選項卡。目前，我正在使用功能viewDidAppear檢查此情況。但是，是否也可以在標籤打開並顯示之前進行每次檢查？

根據第一反應我加入這兩個文件：

MainTabBarController.h

#import <UIKit/UIKit.h> 

@interface MainTabBarController : UITabBarController 

@end 

MainTabBarController.m

#import "MainTabBarController.h" 

@interface MainTabBarController() 

@end 

@implementation MainTabBarController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 
} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

/* 
#pragma mark - Navigation 

// In a storyboard-based application, you will often want to do a little preparation before navigation 
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { 
    // Get the new view controller using [segue destinationViewController]. 
    // Pass the selected object to the new view controller. 
} 
*/ 

- (void)tabBarController:(UITabBarController *)theTabBarController didSelectViewController:(UIViewController *)viewController 
{ 
    NSUInteger indexOfTab = [theTabBarController.viewControllers indexOfObject:viewController]; 

    if(indexOfTab == 2) 
    { 
     NSLog(@"Is it working?"); 
    } 

} 

@end 

Answer 1

在MainTabBarController.m文件，在viewDidLoad中添加委託

@interface MainTabBarController()<UITabBarControllerDelegate> 

然後，添加

self.delegate = self; 

然後添加方法：

- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:  (UIViewController *)viewController 
{ 
    //add your check here 
    return YES; 
} 

Answer 2

是它也可以每天做這種檢查時間前標籤是 打開並顯示？

你需要重寫UITabBarControllerdelegate方法是：

- (void)tabBarController:(UITabBarController *)theTabBarController didSelectViewController:(UIViewController *)viewController { 
    NSUInteger indexOfTab = [theTabBarController.viewControllers indexOfObject:viewController]; 

    if(indexofTab == yourTabIndexToMetCondition){ 
     // Do your stuff here 
    } 

}