如何以編程方式在UITabBarController之間切換

Question

我有一個應用程序與UITabBarController，其中第一個選項卡包含一個主頁的ViewController。我必須做的是在標籤之間切換（這很簡單：[[self tabBarController] setSelectedIndex：index]），AND從「HomePage」中通過selectedTab的出口導航。

只是爲了解釋自己：TabElement1 ---> TabElementX ----> UISegmentedController：segmentY

的問題是，UISegmentedController是零，因爲它尚未初始化（至少是我第一次做操作）。我應該如何解決這個問題？選項卡元素裝有筆尖。

EDIT--下面是一些代碼：

@implementation HomeViewController // Tab Indexed 0 
// ... 
- (void)playVideoPreview { 
NSArray *array; 
array = [[self tabBarController] viewControllers]; 
    // This is a test where I programmatically select the tab AND the switch. 
[[[array objectAtIndex:2] switches] setSelectedSegmentIndex:1]; 
[[self tabBarController] setViewControllers:array]; 
} 
@end 

@implementation TGWebViewController // Tab Indexed 2 
// ... 
@synthesize switches; // In .h file: @property (nonatomic, retain) IBOutlet UISegmentedControl switches; Properly linked within the XIB. 
- (IBAction)switchHasChangedValue { 
    // Foo operations. 
} 

現在我第一次開火playVideoPreview我設法進入選項卡索引2，TGWebViewController，但交換機還不存在，所以我發現我自己分段控件名爲「開關」，並選擇第一個段。如果我回到HomeViewController，然後再次播放playVideoPreview，我會得到正確的行爲。

Answer 1

我已經解決了使用委託和布爾值的問題。現在，當TabBar的索引2處的ViewController加載完成時，它會向其代理髮送一條消息，告知哪些段必須被選中。

編輯下面的代碼（希望它可以幫助）：

// Method in the first View that asks to tab the tab bar to launch the other 
// view controller 

- (void)playVideoPreview { 
NSArray *array; 

array = [[self tabBarController] viewControllers]; 
    if (![[array objectAtIndex:2] catSwitch]) { 
     [[array objectAtIndex:2] setDelegate:self]; 
     [[array objectAtIndex:2] setHasBeenLaunchedByDelegate:YES]; 
    } else { 
     [self selectTab]; 
    } 
    [[self tabBarController] setViewControllers:array]; 
    [[self tabBarController] setSelectedIndex:2]; 
} 

// Now the operations performed by the second View Controller 
- (void)somewhereInYourCode { 
    if (hasBeenLaunchedByDelegate) { 
     [[self delegate] selectTab]; 
    } 
} 

// In the First View Controller this is the delegate method, 
// launched from the Second View Controller 
- (void)selectTab { 
    NSArray *array; 

array = [[self tabBarController] viewControllers]; 
    [[[array objectAtIndex:2] catSwitch] setSelectedSegmentIndex:[[bannerPreview pageControl] currentPage]]; 
} 

// Some declaration 
@protocol SecondViewControllerDelegate; 
class SecondViewController : ViewController { 
    id<TGWebViewControllerDelegate> delegate; 
} 
@end 

@protocol SecondViewControllerDelegate 
    - (void)selectTab; 
@end 

// Meanwhile in the first view 
class FirstViewController : ViewController <SecondViewControllerDelegate> { 
// ... 
}