问题
I have two views that need to be shown modally, one after the other. This doesn't work if we dismiss and show consecutively, like this:
[rootController dismissModalViewControllerAnimated: YES];
[rootController presentModalViewController: psvc animated: YES];
The second modal view simply doesn't show up.
I've seen a fix that was something like this:
[rootController dismissModalViewControllerAnimated: YES];
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[self performSelector: @selector(seekModal) withObject: nil afterDelay: 0.5];
[[UIApplication sharedApplication] endIgnoringInteractionEvents];
The problem is that this won't work all the time (the delay needed is superior, sometimes).
Another possible fix would be to eliminate the animation:
[rootController dismissModalViewControllerAnimated: NO];
[rootController presentModalViewController: psvc animated: YES];
But I'd really like to keep the animation, to keep the feel that the first modal is out of the way. Any suggestions?
回答1:
EDIT: The "correct" mechanism to do this in iOS5+ would be to use the – dismissViewControllerAnimated:completion: method, and present the sequential view controller from the completion block.
The viewcontroller that is being shown modally will have its viewDidDisappear:animated: method called once the modal-dismissal-animation is complete. AFIK this is the only place you can hook to initiate a subsequent presentModalViewController:animated: call.
I have a class that I use for presenting modal view controllers and it implements the logic you're looking for via a callback to the presenting view controller once the dismissal is complete. To use this class, simply alloc/init an instance and present using the normal presentViewController:animated: call. Implement the following method on the presenting view controller:
- (void) modalViewControllerDidDismiss:(UIViewController *)modalViewController
This will be called at once the modal view controller is gone, and you can present a new modal view controller at this time.
One nice thing too - since this class is a specialization of UINavigationController, you can configure the navigationBar on/off as you like. The class also has built-in logic to show a dismiss button, as you like.
Here's the class definition:
@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
And the class implementation:
@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
and, here's how you can use it (in the context of some normal view controller):
- (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];
}
and, here is the dismissal callback method, which presents a new modal view controller:
- (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];
}
回答2:
rootController can tell when the last of the modal view controllers on top of it has disappeared because it will receive a viewDidAppear:. Have you tried linking the presentModalViewController: of the subsequent view controller to that?
回答3:
If you really want to chain multiple view animations together, I would actually suggest just handling the animation logic yourself. It's not too tricky, and then you can have fine-grained control over how the views are presented. I just wrote up something similar for another question here:
iOS -- how do you control the size of a modal view controller?
You can just animate the view on, animate the view off, and when your animationDidStop selector is called, animated your second view on. The nice part of this is you can also play with view opacity and animation direction, as well as decide exactly when the views should appear. For example, you could have the second view come sliding up over the first view as the first view is sliding away; no need to wait for the first one to complete its animation.
回答4:
Is your issue related to "show a modal view inside a modal view" ? I've post an answer about this here : iPhone modal view inside another modal view?
回答5:
The best solution I found for something like this (if they are all equal children of the parent view) is to patch their views onto a UIScrollView with paging enabled, (you can add a page control at the bottom to make it clear and for navigation) then add the views of the controllers to the page view as they come onscreen, remove as they go offscreen.
You may also have to dummy call -viewWillAppear and -viewWillDisappear if the controllers rely on this being called. It feels kinda hack-ish when you're coding it all, but once you have it working it looks smooth and natural, and there isn't any of the waiting associated with animating one view out, then animating the next one in once it is gone.
回答6:
I find using the modal view's -viewDidDissapear to invoke methods on the presenting view controller work's very well. One benefit is the ability to delay deallocation on the modal view controller. Please post any improvements I can make. My inspiration for creating this protocol came from iOS 5's "dismissViewControllerAnimated:completion:" addition to UIViewController. I wanted this functionality in iOS 4.3.
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;
回答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];
}
}];
来源：https://stackoverflow.com/questions/2679910/correct-way-of-showing-consecutive-modalviews