I have a view controller(VC1) embedded in a navigation controller(NAV1). In its viewWillAppear method, I make a call to modally present another view controller. In one case I need the new view controller(VC2) to be presented with animation, and in another case it should be presented without animation. VC2 is also embedded in its own navigation controller(NAV2).
All is fine when the animation flag is set to TRUE. When I set the flag to FALSE, couple of things go wrong:
1. I get the following warning in the console: Presenting view controllers on detached view controllers is discouraged
2. When I move back from VC2 after calling dismissViewControllerAnimated:FALSE completion:nil the viewWillAppear method of VC1 does not get called. It gets called if the animation flag is set to TRUE.
In VC1:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self performSelector:#selector(importStuff:)
withObject:nil];
}
-(void)importStuff
{
//instatntiate VC2
//instantiate NAV2
[Utility presentViewController:pNavController
fromViewController:self
animated:FALSE
completion:nil];
// the above method calls the presentViewController:animated:completion: method
}
IN VC2:
[Utility dismissViewController:self
animated:FALSE
completion:nil];
The above method calls the dismissViewControllerAnimated: method.
Not a solution but a workaround:
You can easily postpone any UI operation to the very next event loop by using afterDelay:0:
[self performSelector:#selector(importStuff:)
withObject:nil
afterDelay:0];
This will give a chance to the current operation to complete.
Furthermore, a delay of 0.4 will match the OS. However, whatever delay you use (other than 0) is a kludge and not guaranteed to work under every situation, device and memory load, etc.
Instead, you should revisit your approach.
Change your design:
Do not run the risk of encountering this animation race in the first place.
You have a couple of options, including:
Controlling the transition animation yourself and waiting for its completion prior pushing another view controller (using a completion signal or completion block)
Changing your methodology entirely to avoid this conundrum altogether
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
[self performSelector:#selector(importStuff) withObject:nil afterDelay:0.1];
}
-(void)importStuff
{
//instatntiate VC2
//instantiate NAV2
SecondViewController *viewMe=[self.storyboard instantiateViewControllerWithIdentifier:#"second"];
[self.view.window.rootViewController presentViewController:viewMe animated:NO completion:nil];
// the above method calls the presentViewController:animated:completion: method
}
Related
I have a UIViewController subclass called NewsViewController which has a completion block property that is called from a button action. The controller is set up and presented in another view controller like this:
newsViewController.completionBlock = ^{
[self dismissViewControllerAnimated:YES completion:nil];
};
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:newsViewController];
[self presentViewController:navigationController animated:YES completion:nil];
In iOS 10 this all works fine, however in iOS 9 the view is not being dismissed. If I put a breakpoint there it does get hit.
I have tried the following without success:
Called it from the main thread (both synchronously and asynchronously)
I have tried it using GCD like this:
dispatch_async(dispatch_get_main_queue(), ^{
[self dismissViewControllerAnimated:YES completion:nil];
});
I have also tried it by putting the dismissal call into a method and then calling
[self performSelectorOnMainThread:#selector(dismissModalView) withObject:nil waitUntilDone:NO];
I don't actually thing the issue is the thread since a call to [NSThread isMainThread] from within the completion block returns YES.
Calling it with a delay
[self performSelector:#selector(dismissModalView) withObject:nil afterDelay:0.1];
Calling dismiss on another view controller
I have tried calling it on navigationController, self.presentedViewController and self.presentingViewController.
Calling dismiss directly from NewsViewController
In the button action where the completion block was called I called [self dismissViewControllerAnimated:YES completion:nil] directly.
Btw. just for fun I tried calling the dismiss method from the completion block of the presentViewController method and there it did get dismissed.
I have finally located the problem and it was quite unexpected. The thing is that the NewsViewController is presented over my login view controller. This controller allows the user to use Touch ID to log in so it requests the Touch ID prompt in its viewDidAppear method. Apparently, this messes with the dismissal of the presented view, and seemingly only in iOS 9 (well, maybe not only, but it seems to work fine in iOS 10).
Try with below code:
newsViewController.completionBlock = ^{
[self performSelector:#selector(Dismiss) withObject:nil afterDelay:0.3];
};
-(void)Dismiss
{
[self dismissViewControllerAnimated:YES completion:^{
}];
}
i have a view controller and i need to dismiss it and present it back in same time.
i had tried dismiss it and call back the view controller but not working.
[self dismissViewControllerAnimated:YES completion:nil];
UIStoryboard *storyboard=[UIStoryboard storyboardWithName:#"Main" bundle:nil];
ExpandViewController *expandView=
[storyboard instantiateViewControllerWithIdentifier:#"ExpandViewController"];
expandView.delegate=self;
[expandView setEventDict:dict];
[self presentViewController:expandView animated:YES completion:NULL];
I am not exactly sure what outcome/functionality you are looking for in your question, but #matt is correct. However, you may be looking to have this happen seamlessly. Therefore you could use child view controllers instead of presenting the view controller using the [self presentViewController:VC animated:animate completion:nil] method.
Adding child vc:
[self addChildViewController:myVC];
[self.view addSubview:myVC.view];
[myVC didMoveToParentViewController:self];
Removing child vc:
[myVC willMoveToParentViewController:nil];
... remove subview.
You can set up a delegate between the two controllers to tell the parent when to dismiss the view to make things easy. You can also add the subviews at different indexes using [self.view insertSubview:myVC atIndex:index] or the other possible functions such as the insert above subview etc, to have one subview be added before dismissing the other to give a more seamless transition.
Hope this helps!
You can't present a view controller until the currently presented view controller has finished being dismissed. You won't know this has happened until the completion handler from your dismissal is called. Your mistake is that the completion handler is nil. Instead, provide a completion handler (in your first line), consisting of the remaining lines of your code. Thus, they will execute after the dismissal finishes.
[self dismissViewControllerAnimated:YES completion:^{
// ... the rest of your code goes in here ...
}];
I have a HomeView and a HomeDropDownView.
HomeDropDownView is shown as a drop-down view over the HomeView.
HomeView is a delegate of HomeDropDownView.
When I do an action in HomeDropDownView I want to call a delegate method in HomeView and have that delegate method present a third view controller, TestViewController from it's navigation controller.
If I try to launch TestViewController from anywhere in the class it works fine - except from the delegate method.
There are animations in HomeDropDownView but putting the call to the delegate method in the complition does not make the view controller appear. And in the case that I'm using this the animation's don't fire anyway; there's only a resizing without animation.
TestViewController's init does get called as well as the viewDidLoad but not the viewWillAppear and the view dose not appear.
Code:
HomeDropDownView
- (void)finalAction {
...
[self callDelegateAction];
...
- (void)calldelegateAction {
if ([self.delegate respondsToSelector:#selector(launchTestView)] ) {
[self.delegate launchTestView];
} else {
DLog(#"Error out to the user.");
}
}
HomeView
- (void)launchTestView {
//[self listSubviewsOfView:self.parentViewController.view];
NSLog(#"delegate method | self: %#", self);
TestViewController *tvc = [[TestViewController alloc] initWithNibName:#"TestViewController" bundle:nil];
//[self.navigationController presentViewController:tvc animated:YES completion:nil];
//[self.view.window.rootViewController presentViewController:tvc animated:YES completion:nil];
//[self.navigationController pushViewController:tvc animated:YES];
AppDelegate *appdelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[appdelegate.tabBarController.navigationController presentViewController:tvc animated:YES completion:^() {
NSLog(#"Done!");
}];
}
None of the above approaches work. But if I put the exact same code into the viewDidAppear or put it in a button action method, it will work fine. At the time of calling the delegate method's self is HomeView and all the subviews, including the nav controller do seem to be there. This is in a tabcontroller-based project but I think that any of the above are acceptable ways to call the nav controller still.
What am I missing? Why does my delegate method not want to push/present a viewcontroller on HomeView's Nav controller? It's probably something I'm missing but I can't find a reason in the Apple Docs or any other thread.
Thanks for the help!
Sadly this turned out to be that HomeView was being changed underneath the execution of the message. So by the time the HomeView got the message call it was no longer the same HomeView object that had requested action in the first place. So it was not the same delegate.
This was done so that it would appear to the user that the same view was being used for different things.
But this is a good example of why you should not destroy and re-create critical views. We should have been using the same view and reloading the objects instead if we knew that we would be sending messages. Or had some notion of a control structure.
I work on a legacy application, and have found out, that my view[Will/Did]Disappear methods are not always fired properly.
The case is, I have a (custom) UIViewController set as rootViewController in AppDelegate. This rootViewController has a UINavigationController, which has two view controllers pushed on it. When the user presses the home button, the user is logged out. When he later returns to the app, the application calls [UINavigationController popToRootViewControllerAnimated:YES] and then displays a modal UIViewController for logging in.
The problem is: When I push/pop on the UINavigationController normally, my viewWillDisappear method is called properly. But when I use the popToRootViewControllerAnimated: method, viewWillDisappear is not called on any of the viewControllers that are popped off.
Searching on the internet has only given two possible reasons:
If using a UINavigationController as a subview, you must call view[Will/Did]Disappear yourself
Not calling the proper super methods
None of these suggestions are the case in my app. And I have no idea where to look. Anybody has a suggestion to what has been done wrong in the app?
The view probably wasn't onscreen. It has to be onscreen (visible) for the viewWillDisappear: method to be called. If it's coming back from the background, it wasn't visible.
You could try using willMoveToParentViewController: which is called when the view controller is removed from its parent.
such useful to me
[nav performSelector:#selector(popToRootViewControllerAnimated:) withObject:nil afterDelay:0.0];
I rewrote UITabBarController
- (void)setSelectedIndex:(NSUInteger)selectedIndex {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.01 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
UINavigationController *navigationController = [originalViewController as:[UINavigationController class]];
if (navigationController.presentedViewController) {
[navigationController dismissViewControllerAnimated:NO completion:^{
[navigationController popToRootViewControllerAnimated:NO];
}];
}else if (navigationController.topViewController){
[navigationController popToRootViewControllerAnimated:NO];
}
});
}
The thing is: I have a modalViewController presented with a button that triggers an IBAction like this:
-(IBAction)myMethod
{
[self dismissModalViewControllerAnimated:YES];
if([delegate respondsToSelector:#selector(presentOtherModalView)])
{
[delegate presentOtherModalView];
}
}
in the root view that is the delegate for that modalViewControllerI've implemented the presentOtherModalView delegate method and it looks like this:
-(void)presentOtherModalView
{
AnotherViewController *viewInstance = [[AnotherViewController alloc]initWithNibName:#"AnotherViewController" bundle:nil];
viewInstance.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentModalViewController:viewInstance animated:YES];
[viewInstance release];
}
The problem is this second modalViewController is not being presented. It gives me the message wait_fences: failed to receive reply: 10004003... How should this be done?
Because they are executed exactly after each other (they don't wait for the view to disappear/appear), it doesn't get executed. Because there can only be one ModalViewController on the screen at a time, you have to first wait for the other ModalViewController to disappear before the next one is put on screen.
You can do this creatively how you want, but the way I did it was something like:
[self dismissModalViewControllerAnimated:YES];
self.isModalViewControllerNeeded = YES;
And then in the underlying ViewController, in the viewDidAppear method, I do this:
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if (self.isModalViewControllerNeeded) {
[self presentModalViewController:viewInstance animated:YES];
self.isModalViewControllerNeeded = NO;
}
}
Hope it helps!
It is because the dismissModalViewControllerAnimated takes some time to dismiss with animation and you are calling another view to present as modal view before dismissing the 1st modal view so the presenting modal view call was rejected. You should not perform animations when you are not on the view after completely dismissing only you can call another view. To solve this problem call the present modal view after 2 or 3 seconds using time interval or use completion block for dismissModalViewControllerAnimated
You can achieve it by using this
[delegate performSelector:#selector(presentOtherModalView) withObject:nil afterDelay:3];