显示连续模态视图的正确方法

Question

我有两个视图需要以模态方式显示，一个接一个。如果我们连续关闭并显示，这将不起作用，如下所示：

[rootController dismissModalViewControllerAnimated: YES];
[rootController presentModalViewController: psvc animated: YES];

第二个模态视图根本不显示。

我见过这样的修复：

[rootController dismissModalViewControllerAnimated: YES];
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[self performSelector: @selector(seekModal) withObject: nil afterDelay: 0.5];
[[UIApplication sharedApplication] endIgnoringInteractionEvents];

问题是这不会一直有效（有时所需的延迟是优越的）。

另一个可能的修复方法是消除动画：

[rootController dismissModalViewControllerAnimated: NO];
[rootController presentModalViewController: psvc animated: YES];

但我真的很想保留动画，以保持第一个模式不妨碍的感觉。有什么建议吗？

Answer 1

编辑：在iOS5+中执行此操作的“正确”机制是使用–dismissViewControllerAnimated:completion:方法，并从完成块中呈现顺序视图控制器。

---

一旦模态解除动画完成，以模态方式显示的视图控制器将调用其 viewDidDisappear:animated: 方法。 AFIK 这是您可以挂钩以启动后续的presentModalViewController:animated: 调用的唯一地方。

我有一个用于呈现模式视图控制器的类，一旦解除完成，它就会通过回调呈现视图控制器来实现您正在寻找的逻辑。要使用此类，只需分配/初始化一个实例并使用正常的 presentViewController:animated: 调用来呈现。在呈现视图控制器上实现以下方法：

- (void) modalViewControllerDidDismiss:(UIViewController *)modalViewController

一旦模态视图控制器消失，就会调用该方法，此时您可以呈现一个新的模态视图控制器。

还有一件好事 - 由于此类是 UINavigationController 的特化，因此您可以根据需要配置导航栏开/关。该类还具有内置逻辑，可以根据需要显示关闭按钮。

这是类定义：

@protocol TSModalViewControllerDelegate

- (void) modalViewControllerDidDismiss: (UIViewController*) modalViewController;

@end

@interface TSModalViewController : UINavigationController 
{
    UIViewController*   _originalParentViewController;
}
@property BOOL dismissButtonHidden;

- (id) initWithViewController: (UIViewController*) vc;
- (id) initWithClass: (Class) c;
- (id) initWithClass: (Class) c nibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil;

@end

以及类实现：

@implementation TSModalViewController
@synthesize dismissButtonHidden;

- (id) initWithViewController: (UIViewController *)vc
{
    return [super initWithRootViewController: vc];
}

- (id) initWithClass:(Class)c
{
    UIViewController* vc = [[[c alloc] init] autorelease];
    return [self initWithViewController: vc];
}

- (id) initWithClass: (Class) c nibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    UIViewController* vc = [[[c alloc] initWithNibName:nibNameOrNil bundle:nibBundleOrNil] autorelease];
    return [self initWithViewController: vc];
}

- (void) viewDidAppear: (BOOL) animated
{
    [super viewDidAppear: animated];

    [_originalParentViewController release];
    _originalParentViewController = [self.parentViewController retain];

    if (!self.dismissButtonHidden)
    {
        UIBarButtonItem* dismissButton = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem: UIBarButtonSystemItemStop
                                                                                        target: self 
                                                                                        action: @selector(onDismiss:)] autorelease];

        UIViewController* rootViewController = [self.viewControllers objectAtIndex:0];

        rootViewController.navigationItem.leftBarButtonItem = dismissButton;
        self.navigationBarHidden = NO;
    }   
}

- (void) viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear: animated];
    if ( [_originalParentViewController respondsToSelector: @selector(modalViewControllerDidDismiss:)] )
    {
        [_originalParentViewController performSelector: @selector(modalViewControllerDidDismiss:) withObject: self];
    }
}

- (void) dismissModalViewControllerAnimated:(BOOL)animated
{
    return [self.parentViewController dismissModalViewControllerAnimated: animated];
}

- (void) onDismiss: (id) sender
{
    [self.parentViewController dismissModalViewControllerAnimated: YES];
}

- (void) didReceiveMemoryWarning 
{
    [super didReceiveMemoryWarning];
}

- (void) viewDidUnload 
{
    [super viewDidUnload];
}

- (void)dealloc 
{
    [_originalParentViewController release];
    [super dealloc];
}

@end

并且，这是如何使用它（在某些普通视图控制器的上下文中）：

- (void) onShowIt:(id)sender
{
    TSModalViewController* mvc = [[[TSModalViewController alloc] initWithClass: [MyModalViewController class] nibName: @"MyModalViewController" bundle:nil] autorelease];
    mvc.dismissButtonHidden = YES;  // set to no if you don't want an "automatic" close button

    [self presentModalViewController: mvc animated: YES];
}

并且，这是解雇回调方法，它呈现了一个新的模式视图控制器：

- (void) modalViewControllerDidDismiss:(UIViewController *)modalViewController
{
    MyModalViewController* vc = [[[MyModalViewController alloc] initWithNibName: @"MyModalViewController" bundle:nil] autorelease];
    vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

    TSModalViewController* mvc = [[[TSModalViewController alloc] initWithViewController: vc] autorelease];

    [self presentModalViewController: mvc animated: YES];
}

Answer 2

rootController 可以判断其顶部的最后一个模态视图控制器何时消失，因为它将收到 viewDidAppear:。您是否尝试过将后续视图控制器的 presentModalViewController: 链接到该控制器？

Answer 3

如果您确实想将多个视图动画链接在一起，我实际上建议您自己处理动画逻辑。这并不太棘手，然后您可以对视图的呈现方式进行细粒度的控制。我刚刚在这里为另一个问题写了类似的内容：

iOS -- 如何控制模态视图控制器的大小？

你可以只对视图进行动画显示，对视图进行动画关闭，当你的animationDidStop选择器被调用时，对你的第二个视图进行动画处理视图上。这样做的好处是您还可以使用视图不透明度和动画方向，以及准确决定视图何时应出现。例如，当第一个视图滑开时，您可以让第二个视图在第一个视图上向上滑动；无需等待第一个动画完成。

Answer 4

您的问题与“在模态视图内显示模态视图”相关吗？
我在这里发布了有关此问题的答案：
iPhone 模态视图位于另一个模态视图内？

Answer 5

我发现对于这样的事情（如果它们都是父视图的相同子级）的最佳解决方案是将它们的视图修补到启用分页的 UIScrollView 上，（您可以在底部添加一个页面控件以使其清晰并用于导航）然后在控制器的视图出现在屏幕上时将它们添加到页面视图中，在它们离开屏幕时将其删除。

如果控制器依赖于此调用，您可能还必须虚拟调用 -viewWillAppear 和 -viewWillDisappear。当你对所有内容进行编码时，感觉有点像黑客，但是一旦你让它工作起来，它看起来就很流畅和自然，并且没有任何与将一个视图动画化出来然后将下一个视图动画化相关的等待。消失了。

Answer 6

我发现使用模态视图的 -viewDidDissapear 来调用呈现视图控制器上的方法效果非常好。好处之一是能够延迟模态视图控制器上的释放。请发布我可以做出的任何改进。
我创建这个协议的灵感来自于 iOS 5 对 UIViewController 的“dismissViewControllerAnimated:completion:”补充。我希望在 iOS 4.3 中提供此功能。

---

PresentorDelegateProtocol.h

@protocol PresentorDelegateProtocol <NSObject>
@optional

/* 

Extra protocol methods defined in protocol for flexibility.  
Main methods are:
- (void)dismissPresentingModalViewController:(id)modalView animated:(BOOL)animated; 
- (void)modalViewDissapeared:(id)modalView;  //used in modal view's -viewDidDissapear

*/

- (void)dismissPresentingModalViewController:(id)modalView animated:(BOOL)animated;
- (void)modalViewDissapeared:(id)modalView; 

// use the block in this method send messages to save state, etc.  This is the one I like to use.
- (void)dismissPresentingModalViewController:(id)modalView animated:(BOOL)animated withBlock:(void(^)())block;

// use in other classes that are not controlling dismissal of the modal view
- (void)executeBlockOnModalDissapearance: (void(^)())block;

@end

---

PresentingViewController.h

#import "PresentorDelegateProtocol.h"
@interface PresentingViewController : UIViewController <PresentorDelegateProtocol>
- (void)showModalVC;
@end

---

ModalViewController.h

#import "PresentorDelegateProtocol.h"
@interface ModalViewController : UIViewController
@property (nonatomic, assign) id <PresentorDelegateProtocol> presentorDelegate;
- (void)close;
@end

---

PresentingViewController.m

#import "PresentingViewController.h"
#import "ModalViewController.h"
@implementation PresentingModalViewController
- (void)showModalVC
{
    ModalViewController *modalVC = [[ModalViewController alloc] initWithNibName:@"ModalViewController" bundle:nil];
    modalVC.presentorDelegate = self;
    [self presentModalViewController:modalVC animated:YES];
}
- (void)dismissPresentingModalViewController:(id)modalView animated:(BOOL)animated
{
    if ([modalView isKindOfClass:[ModalViewController class]]) {
        NSLog(@"Can invoke based on class"); 
    }
    [self dismissModalViewControllerAnimated:animated];    
}
- (void)dismissPresentingModalViewController:(id)modalView animated:(BOOL)animated withBlock:(void(^)())block
{
    block();  
    /* execute block before or after calling to dismiss modal view */
    [self dismissPresentingModalViewController:modalView animated:animated];
    //block();
}
- (void)modalViewDissapeared:(id)modalView
{
    if ([modalView isKindOfClass:[ModalViewController class]]) {
        NSLog(@"Do stuff based on class.");
    }
}
- (void)executeBlockOnModalDissapearance: (void(^)())block
{
    block();
    NSLog(@"This delay's dealloc on modal view until block completes");
}
@end

---

ModalViewController.m

#import "ModalViewController.h"
@implementation ModalViewController
@synthesize presentorDelegate;

- (void)close
{
    if (1 == 0 /*need to do something before dealloc*/){
        [self.presentorDelegate dismissPresentingModalViewController:self animated:YES withBlock:^{
            NSLog(@"Do stuff with block.  Save, animate, etc");
        }];

    } else {
        [self.presentorDelegate dismissPresentingModalViewController:self animated:YES];
    }
}

- (void)viewDidDisappear:(BOOL)animated
{
    if (1 == 0 /*stuff to do*/){
        [self.presentorDelegate executeBlockOnModalDissapearance:^{
        // do stuff before modal view is deallocated
        }];
    }
    [self.presentorDelegate modalViewDissapeared:self];

    presentorDelegate = nil;
    [super viewDidDisappear:animated];
}
@end;

Answer 7

// present modal view inside another presented modal view

    FirstViewController *firstVC = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController: firstVC];

    // Note: you can use your viewcontroller instead self.window.rootViewController

    [self.window.rootViewController presentViewController:navController animated:YES completion:^{
                //code...
                    SecondViewController *secondVC = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];

                    [navController presentViewController: secondVC animated:YES completion:nil];

                }
            }];