在模態視圖控制器之間切換

Question

我的應用程序允許用戶在兩​​個不同的模態視圖控制器（用於兩種不同類型的數據輸入）之間切換。下面的代碼用來工作（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） - 「當前」視圖控制器駁回，但「SVC」不被呈現。

任何想法爲什麼它壞了（即我做錯了什麼）？ 任何想法如何做到「正確」（這樣它可以在5.0以及4.3和更早的版本上工作）？

Answer 1

傑夫海在他的評論中完全正確，除了一件事。您應該在視圖控制器的-viewDidAppear:方法中執行此操作，該視圖控制器最初提供了第一個模式視圖控制器。

實施例：

// 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 

編輯：
現在，如果要在兩個模態的視圖控制器之間傳遞數據，就可以使用一個委託。

// 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