Utilizzo del contenimento del controller di visualizzazione, i figli perdono il genitore

Question

Nuovo sviluppatore iOS che scrive la prima app commissionata per iPhone.

Il controller di visualizzazione genitore chiamato modamente ha sei figli che vengono trasferiti utilizzando un controllo segmentato nel padre. Sto ottenendo l'errore:

bambini visualizzare i controller e devono avere una vista di controllo genitore comune al momento della chiamata - [UIViewController transitionFromViewController: toViewController: durata: opzioni: animazioni: completamento:]

Quando si preme un secondo pulsante, cioè posso premere qualsiasi pulsante dopo che il genitore è presentato e funziona. Ma la prossima volta che premo un nuovo pulsante, ottengo il crash sopra. Usando NSLogs ho determinato che il motivo del crash è che sia il bambino attuale che quello nuovo hanno perso il genitore tra le pressioni dei pulsanti. Non ho idea del perché. Codice relevent per il genitore segue: codice

Interfaccia: codice

#import <UIKit/UIKit.h> 
#import "WorksheetScrollViewController.h" 
#import "Worksheet1ViewController.h" 
#import "Worksheet2ViewController.h" 
#import "Worksheet3ViewController.h" 
#import "Worksheet4ViewController.h" 
#import "WorksheetEndViewController.h" 


@interface WorkSheetParentViewController : UIViewController 
{ 
IBOutlet UISegmentedControl *segControl; 
IBOutlet UIBarButtonItem *doneButton; 
IBOutlet UIView *childContainerView; 

WorksheetScrollViewController *wStart; 
Worksheet1ViewController *w1; 
Worksheet2ViewController *w2; 
Worksheet3ViewController *w3; 
Worksheet4ViewController *w4; 
WorksheetEndViewController *wEnd; 

UIViewController *currentVC; 
UIViewController *newVC; 

} 


-(void)initToolbar; 
-(IBAction) doneButtonPressed:(id)sender; 
-(IBAction) segControlChanged:(id)sender; 

-(void)swapViewControllers; 

Implementazione:

- (void)viewDidLoad 
{ 
[super viewDidLoad]; 
// Do any additional setup after loading the view from its nib. 
wStart = [[WorksheetScrollViewController alloc  ]initWithNibName:@"WorksheetScrollViewController" bundle:nil]; 

[self addChildViewController:wStart]; 
wStart.view.frame=childContainerView.bounds; 

[childContainerView addSubview:wStart.view]; 
[wStart didMoveToParentViewController:self]; 
currentVC = wStart; 

} 

- (IBAction) segControlChanged:(id)sender 

{ 

NSLog(@"selected tab bar item:%i",segControl.selectedSegmentIndex); 
switch (segControl.selectedSegmentIndex) { 
    case 0: 
     if (!wStart) { 
      wStart = [[WorksheetScrollViewController alloc ]initWithNibName:@"WorksheetScrollViewController" bundle:nil]; 
     } 
     newVC = wStart; 
     break; 

    case 1: 
     if (!w1) { 
      w1 = [[Worksheet1ViewController alloc ]initWithNibName:@"Worksheet1ViewController" bundle:nil]; 
     } 
     newVC = w1; 
     break; 

    case 2: 
     if (!w2) { 
      w2 = [[Worksheet2ViewController alloc ]initWithNibName:@"Worksheet2ViewController" bundle:nil]; 
     } 
     newVC = w2; 
     break; 

    case 3: 
     if (!w3) { 
      w3 = [[Worksheet3ViewController alloc ]initWithNibName:@"Worksheet3ViewController" bundle:nil]; 
     } 
     newVC = w3; 
     break; 

    case 4: 
     if (!w4) { 
      w4 = [[Worksheet4ViewController alloc ]initWithNibName:@"Worksheet4ViewController" bundle:nil]; 
     } 
     newVC = w4; 
     break; 

    case 5: 
     if (!wEnd) { 
      wEnd = [[WorksheetEndViewController alloc ]initWithNibName:@"WorksheetEndViewController" bundle:nil]; 
     } 
     newVC = wEnd; 
     break; 


    default: 
     break; 
} 
[self swapViewControllers]; 


} 

-(void)swapViewControllers 
{ 
NSLog(@"top current VC parent = %@",currentVC.parentViewController); 
NSLog(@"top new VC parent = %@",newVC.parentViewController); 
[currentVC willMoveToParentViewController:nil]; 
newVC.view.frame=childContainerView.bounds; 

[self addChildViewController:newVC]; 

NSLog(@"current VC parent = %@",currentVC.parentViewController); 
NSLog(@"new VC parent = %@",newVC.parentViewController); 
[self transitionFromViewController:currentVC 
        toViewController:newVC 
          duration:1.0 
          options:UIViewAnimationOptionTransitionCurlUp 
         animations:nil 
         completion:^(BOOL finished) { 
          [currentVC removeFromParentViewController]; 
          [newVC didMoveToParentViewController:self]; 

         }]; 
currentVC = newVC; 
NSLog(@"bottom current VC parent = %@",currentVC.parentViewController); 
NSLog(@"bottom new VC parent = %@",newVC.parentViewController); 

} 

NSLog risultati per il tasto 1, quindi il tasto 2:

2013-08-26 14:49:07.245 Alveolar Gas iPhone[556:707] selected tab bar item:1 
2013-08-26 14:49:07.251 Alveolar Gas iPhone[556:707] top current VC parent =  <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:49:07.256 Alveolar Gas iPhone[556:707] top new VC parent = (null) 
2013-08-26 14:49:07.437 Alveolar Gas iPhone[556:707] current VC parent = <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:49:07.440 Alveolar Gas iPhone[556:707] new VC parent = <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:49:07.460 Alveolar Gas iPhone[556:707] bottom current VC parent = <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:49:07.462 Alveolar Gas iPhone[556:707] bottom new VC parent = <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:49:13.984 Alveolar Gas iPhone[556:707] selected tab bar item:2 
2013-08-26 14:49:33.912 Alveolar Gas iPhone[556:707] top current VC parent = (null) 
2013-08-26 14:49:50.038 Alveolar Gas iPhone[556:707] top new VC parent = (null) 
2013-08-26 14:55:36.149 Alveolar Gas iPhone[556:707] current VC parent = (null) 
2013-08-26 14:55:36.153 Alveolar Gas iPhone[556:707] new VC parent = <WorkSheetParentViewController: 0x198da0> 
2013-08-26 14:55:36.160 Alveolar Gas iPhone[556:707] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Children view controllers <Worksheet1ViewController: 0x1ea780> and <Worksheet2ViewController: 0x1403b0> must have a common parent view controller when calling -[UIViewController transitionFromViewController:toViewController:duration:options:animations:completion:]' 

Answer 1

Ho sistemato spostando currentVC = newVC; nel blocco di completamento. SwapViewControllers: ora è il seguente:

-(void)swapViewControllers 
{ 
NSLog(@"top current VC parent = %@",currentVC.parentViewController); 
NSLog(@"top new VC parent = %@",newVC.parentViewController); 
[currentVC willMoveToParentViewController:nil]; 
newVC.view.frame=childContainerView.bounds; 

[self addChildViewController:newVC]; 

NSLog(@"current VC parent = %@",currentVC.parentViewController); 
NSLog(@"new VC parent = %@",newVC.parentViewController); 
[self transitionFromViewController:currentVC 
        toViewController:newVC 
          duration:1.0 
          options:UIViewAnimationOptionTransitionCurlUp 
         animations:nil 
         completion:^(BOOL finished) { 
          [currentVC removeFromParentViewController]; 
          [newVC didMoveToParentViewController:self]; 
          currentVC = newVC; 
         }]; 

NSLog(@"bottom current VC parent = %@",currentVC.parentViewController); 
NSLog(@"bottom new VC parent = %@",newVC.parentViewController); 

}