在模态视图控制器之间切换

Question

我的应用程序允许用户在两​​个不同的模态视图控制器（用于两种不同类型的数据输入）之间切换。下面的代码用来工作（在IOS 4.3或更早）：

UIViewController * parent = current.parentViewController; 
    [current dismissModalViewControllerAnimated:NO]; 
    svc.modalPresentationStyle = UIModalPresentationFormSheet; 
    [parent presentModalViewController:svc animated:NO]; 
    [svc release]; 

但不再（在IOS 5） - “当前”视图控制器驳回，但“SVC”不被呈现。

任何想法为什么它坏了（即我做错了什么）？ 任何想法如何做到“正确”（这样它可以在5.0以及4.3和更早的版本上工作）？

Answer 1

杰夫海在他的评论中完全正确，除了一件事。您应该在视图控制器的-viewDidAppear:方法中执行此操作，该视图控制器最初提供了第一个模式视图控制器。

实施例：

// MyViewController.h 
@interface MyViewController : UIViewController { 
    BOOL _shouldPresentSecondModalViewController; 
} 
@end 

---

// MyViewController.m 
@implementation MyViewController 
- (void)viewDidAppear:(BOOL)animated { 
    if(_shouldPresentSecondModalViewController) { 
     UINavigationController *myNavCon; 
     // Code to create second modal navigation controller 
     [self presentModalViewController:myNavCon animated:YES]; 
     _shouldPresentSecondModalViewController = NO; 
    } 
} 

- (void)presentFirstViewController { 
    UINavigationController *myNavCon; 
    // Code to create the first navigation controller 
    _shouldPresentSecondModalViewController = YES; 
    [self presentModalViewController:myNavCon animated:YES]; 
} 
@end 

编辑：
现在，如果要在两个模态的视图控制器之间传递数据，就可以使用一个委托。

// FirstModalViewControllerDelegate.h 
@protocol FirstModalViewControllerDelegate 
@optional 
- (void)controller:(FirstModalViewControllerDelegate *)vc shouldShowData:(id)anyType; 
@end 

---

// MyViewController.h 
@interface MyViewController : UIViewController <FirstModalViewControllerDelegate> { 
    id _dataToDisplay; 
} 
@end 

---

// MyViewController.m 
@implementation MyViewController 
- (void)viewDidAppear:(BOOL)animated { 
    if(_dataToDisplay != nil) { 
     UINavigationController *myNavCon; 
     // Code to create second modal navigation controller 
     [self presentModalViewController:myNavCon animated:YES]; 
     [_dataToDisplay release]; 
     _dataToDisplay = nil; 
    } 
} 

- (void)presentFirstViewController { 
    UINavigationController *myNavCon; 
    FirstModalViewController *myCon; 
    // Code to create the first modal view controller 

    [myCon setDelegate:self]; 

    myNavCon = [[UINavigationController alloc] initWithRootViewController:myCon]; 

    [self presentModalViewController:myNavCon animated:YES]; 
    [myNavCon release]; 
} 

- (void)controller:(FirstModalViewControllerDelegate *)vc shouldShowData:(id)anyType { 
    /* This method will get called if the first modal view controller wants to display 
    some data. If the first modal view controller doesn't call this method, the 
    _dataToDisplay instance variable will stay nil. However, in that case, you'll of 
    course need to implement other methods to, like a response to a Done button, dismiss 
    the modal view controller */ 
    [self dismissModalViewController]; 
    _dataToDisplay = [anyType retain]; 
} 
@end