如何以编程方式在UITabBarController之间切换

Question

我有一个应用程序与UITabBarController，其中第一个选项卡包含一个主页的ViewController。我必须做的是在标签之间切换（这很简单：[[self tabBarController] setSelectedIndex：index]），AND从“HomePage”中通过selectedTab的出口导航。

只是为了解释自己：TabElement1 ---> TabElementX ----> UISegmentedController：segmentY

的问题是，UISegmentedController是零，因为它尚未初始化（至少是我第一次做操作）。我应该如何解决这个问题？选项卡元素装有笔尖。

EDIT--下面是一些代码：

@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. 
} 

现在我第一次开火playVideoPreview我设法进入选项卡索引2，TGWebViewController，但交换机还不存在，所以我发现我自己分段控件名为“开关”，并选择第一个段。如果我回到HomeViewController，然后再次播放playVideoPreview，我会得到正确的行为。

Answer 1

我已经解决了使用委托和布尔值的问题。现在，当TabBar的索引2处的ViewController加载完成时，它会向其代理发送一条消息，告知哪些段必须被选中。

编辑下面的代码（希望它可以帮助）：

// 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> { 
// ... 
}