I have a ViewController, HomeVC, who manages the transition between three other view controllers, PhotopickerVC, CroppingVC and EditingVC.
As HomeVC dismisses one VC and presents another VC, I get an undesired effect in which HomeVC is visible for a fraction of a second between these transitions.
Here is a little more details about my code.
The normal flow of the app is HomeVC → PhotopickerVC → CroppingVC → EditingVC (both PhotopickerVC and CroppingVC are only assisting in getting to the final EditingVC, they are no longer required after they are dismissed).
I implement this flow using segues from the HomeVC in the following form:
Starting from HomeVC visible, Photo button is pressed, a (subclassed) UIImagePickerController is created and presented.
When photo was chosen, (subclassed) UIImagePickerController calls [picker dismissViewControllerAnimated:NO completion:nil]; This takes us back to HomeVC
In HomeVC method viewWillAppear, I call [self performSegueWithIdentifier:#"CroppingVC" sender:self];
In CroppingVC, when user presses Accept button, CroppingVC calls [self dismissViewControllerAnimated:NO completion:nil]; This takes us back to HomeVC
In HomeVC viewWillAppear, I call [self performSegueWithIdentifier:#"EditingVC" sender:self];
In EditingVC, when the user presses Home, EditingVC calls [self dismissViewControllerAnimated:YES completion:nil]; This takes us back to HomeVC.
From what I see, you do not really need the HomeVC to manage transitions. What you should do, is to make the VC hierarchy exactly as you wrote:
HomeVC → PhotopickerVC → CroppingVC → EditingVC
The arrows should be eg. push segues, and then in the prepareForSegue method you can just pass all the necessary parameters.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
YourViewController *destinationController = (YourViewController *)segue.destinationViewController;
// do sth
}
This way you can achieve nice and smooth transitions. The way your application is now seems to have a structural flaw, because as you have said, when a ViewController gets used once, it is not needed anymore. After that you can just return to the HomeVC.
Related
I launch a modal view controller VCM embedded in a Navigation controller from VC1.
The modal VC has a button to go to another View Controller, VC2.
if the user presses the button to go to VC2, I need to simultaneously dismiss the modal and also change the sending from VC1 to VC2. (It's important to dismiss the modal to get rid of it, so I don't have VCs accumulating on the stack.)
Here is the action method in the modal attached to the VC2 button.
- (IBAction)VC2ButtonPressed:(id)sender {
[self dismissViewControllerAnimated:true completion:nil];
//Above line works fine
[VC1 performSegueWithIdentifier:#"showVC2" sender:VC1];//No known class method error
}
I can dismiss the modal without any problem (first line) but can't figure out how to simultaneously segue to VC2. There is a storyboard segue in VC1 named 'showVC2' for what it's worth. I do not have any relevant class methods currently in the sending VC. Should I create a special class method? Or how can I invoke a method in the VC that launched the modal.
Edit:
I also tried:
[self.presentingViewController performSegueWithIdentifier:#"showVC2" sender:self];
This compiles but gives runtime error () has no segue with identifier 'showVC2''
I think this is because VC2 is embedded in a tabbarcontroller.
Edit2:
I tried putting code in completion handler as suggested by #Oscar but while code gets fired, VC2 does not load
[self dismissViewControllerAnimated:YES completion:^{
[self gotoVC2];
}];
new method
-(void)gotoVC2 {
LogDebug(#"gotoVC2 called");//DOES log to console
UIStoryboard *storyBoard = self.storyboard;
IDFeedVC *VC2 =
[storyBoard instantiateViewControllerWithIdentifier:#"vc2"];
[self presentViewController:VC2 animated:YES completion: nil];
}
Thanks for any ideas.
When a logged in user opens my application, they are sent to the main TabBarController from my AppDelegate, like so:
UITabBarController *tabBar = (UITabBarController *)self.window.rootViewController;
tabBar.selectedIndex = 2;
// (this is MainViewController in the tab bar)
Now, the user is in MainViewController. When the user selects a particular chat they'd like to enter, they are sent to the ChatViewController (not on the TabBarController), like so:
[self performSegueWithIdentifier:#"showChatSeg" sender:self];
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([segue.destinationViewController isKindOfClass:ChatViewController.class]){
ChatViewController *destinationViewController = (ChatViewController *)segue.destinationViewController;
if(self.createdDialog != nil){
destinationViewController.dialog = self.createdDialog;
self.createdDialog = nil;
}else{
QBChatDialog *dialog = [ChatService shared].dialogs[self.selectedChat];
destinationViewController.dialog = dialog;
}
}
}
When this happens, I see a spike in memory usage, which makes sense. However, when the user leaves the ChatViewController and return to the MainViewController, like so:
- (IBAction)backButton:(id)sender {
[self performSegueWithIdentifier:#"fromChatToDashSeg" sender:nil];
// This is a storyboard segue back to the MainTabBarController
}
I get the following warning:
Attempt to present <MainTabBarController: 0x17ef28d0> on <ChatViewController: 0x17d6c940> whose view is not in the window hierarchy!
And the memory usage remains the same. And when the user enters a chat again, the memory continues to increase. Am I not dismissing the sending view controllers properly?
What you are doing is not going "back" but rather, you are presenting a copy of the previous view on top of the one you already have. That's why memory is building up, because you just keep stacking more and more views on top of eachother. Assuming you are using a modal segue to present your chat view, try calling:
[self dismissViewControllerAnimated:YES completion:nil];
It's because you're trying to perform a segue just to get back to your original location. All you need to do is dismiss your current modal view controller by calling [self dismissViewControllerAnimated:YES completion:nil];. Whenever you add a modal view to the view stack you want to call this method to exit, unless your intent is to add yet another view on top of the modal.
WLINewPostViewController *newPostViewController = [[WLINewPostViewController alloc] initWithNibName:#"WLINewPostViewController" bundle:nil];
UINavigationController *newPostNavigationController = [[UINavigationController alloc] initWithRootViewController:newPostViewController];
newPostNavigationController.navigationBar.translucent = NO;
[tabBarController presentViewController:newPostNavigationController animated:YES completion:nil];
So I just simply push a new UIViewController.
Then after it posts the server callback calls a method with this code from the WLINewPostViewController.m:
[self dismissViewControllerAnimated:YES completion:^{
NSLog(#"Completed");
}];
[[self navigationController] popViewControllerAnimated:YES];
if (self == self.navigationController.visibleViewController){
NSLog(#"self = visibile");
}
if (self == self.presentingViewController.presentingViewController){
NSLog(#"self = presenting");
}
}
I tried a bunch of different things and none work.
I am relatively new to Xcode but after trying
[self dismissViewControllerAnimated:YES completion]
[self.navigationController popViewControllerAnimated:YES]
[self.navigationController.visibleViewController.presentedViewController dismissViewControllerAnimated:YES completion:nil];
[self.navigationController dismissViewControllerAnimated:YES completion:nil];
and every other possibility, I am officially stumped. The WLINewPostViewController still won't dismiss.
It Logs out "self = visible"
Let me illustrate what you are trying to do
You have a navigation controller with Controller A.
Here you are trying to present another Controller B from Controller A.
Now when you get a callback from the server, you should call dismissViewControllerAnimated from Controller B to dismiss itself.
So after dismissViewControllerAnimated:completion: method call, the Controller B will be dismissed and Controller A will be shown automatically. Now you do not need to call popViewControllerAnimated: in completion block again as there is no other Controller in navigation controller to load.
If you have different use case, let me know I can provide solution.
You are presenting a view over navigationbar instead of pushing it over navigationbar.
When push you pop. When you present you dismiss. So instead of popViewControllerAnimated you need to use dismissViewControllerAnimated:completion
dismiss behaves differently depending on the receiver. From the docs:
The presenting view controller is responsible for dismissing the view controller it presented. If you call this method on the presented view controller itself, it automatically forwards the message to the presenting view controller.
If you present several view controllers in succession, thus building a stack of presented view controllers, calling this method on a view controller lower in the stack dismisses its immediate child view controller and all view controllers above that child on the stack. When this happens, only the top-most view is dismissed in an animated fashion; any intermediate view controllers are simply removed from the stack. The top-most view is dismissed using its modal transition style, which may differ from the styles used by other view controllers lower in the stack.
In short, if the vc on top calls it on itself, it dismisses itself. Anywhere else on the stack dismisses to that point, animating only the topmost vc.
What's extra confusing (for you and many others) is that the navigation vc has a stack too, and your problem is complicated further by presenting an navigation vc atop a tab-bar vc.
So what to do? The question is unclear about which vc is the receiver in the posted code (who is self in that snippet?). The text implies that self is a vc on the stack of the presented navigation vc, like...
TabBarVC --- presents ---> NavVC
| |
| --- viewControllers stack = rootVC, vc1
|
---> viewControllers for each tab
... and it's root or vc1 that wants to dismiss. If I'm right about that, then, given the docs, the solution is clear:
[self.navigationController dismissViewControllerAnimated:YES completion:^{}];
will put us back on the tabbar vc on whatever tab was visible when we did the present.
Im trying to dismiss a ModaViewController called C, back to A. The ModalViewController is presented in B. Therefore the Navigation flow is A->B - (present ModalView) -> C. I am able to dismiss the ModalViewController back to B, but I am unable to pop back to A in the completion bracket. This is the code I have tried:
[self dismissViewControllerAnimated:YES completion:^{
[self.navigationController popToViewController:[[self.navigationController viewControllers] objectAtIndex:0] animated:YES];
}];
The ModalViewController is dismissed but does not pop back to A. I call this block of code in an IBAction.
Any advice?
On a second note, when I dismiss the ModalViewController all my UIPickers in Controller B are empty/ deallocated. I am using ARC as well.
The problem with your code is that self.navigationController will be nil. If you have a controller (A) embedded in a navigation controller, and that controller pushes to another controller (B) which then presents your last controller (C), then you need to do something like this,
-(IBAction)dismissToBThenPop:(id)sender {
UINavigationController *nav = (UINavigationController *)self.presentingViewController;
[self dismissViewControllerAnimated:YES completion:^{
[nav popViewControllerAnimated:YES];
}];
}
Even though you present C from B, the actual presentingViewController will be the navigation controller. This code will dismiss C then pop B, but you will see B for an instant before ut pops back to A. If you don't want to see this, then you should use an unwind segue to go directly back to A from C.
Your second problem about the pickers being empty and deallocated should not be happening under the scenario that you say you have. You will have to provide more information about what you're doing in B to solve that problem.
Create a protocol in ModalViewController, let's say ModalViewControllerDelegate with a method -(void)dismissTheModal, and make B implement this protocol. Before showing the ModalViewController, do modalViewController.delegate = self. When you're IBAction is called, do [self.delegate dismissTheModal], and in controller B you should do :
-(void)dismissTheModal {
[self dismissViewControllerAnimated:YES completion:^{
[self popViewController];
}];
I have an iOS app that has a log in view (LognnViewController) and once a user is successfully authenticated they are taken to another view (DetailEntryViewController) to enter some simple details.
Once the details are entered the user is taken to the main part of the app that consists of a tab controller (TabViewController) that holds a variety of other views. The LogInViewController performs a modal segue to the DetailEntryViewController and the DetailEntryViewController then performs a modal segue to the TabViewController so I have kind of a modal segue chain going to get into the app. When a user logs out I want to go all the way back to the LogInViewController but when I do a:
[self.presentingViewController dismissModalViewControllerAnimated:YES];
...it pops the TabViewController and I end up back at the DetailEntryViewController instead of the first LogInViewController. Is there any way I can pop back to the first view controller easily or does doing this modal segue chain thing prevent me from that. I got the bright idea to put some code in the DetailEntryViewController viewWillAppear: that would automagically pop itself if the user had logged out but apparent making calls to dismiss a modal controller are not allowed in viewWillAppear: viewDidLoad:, etc.
Any ideas on how to make this happen?
I think this is not the best structure to implement your app. Modal controllers are supposed to be for temporary interruptions to the flow of the program, so using a modal to get to your main content is not ideal. The way I would do this is to make your tab bar controller the root view controller of the window, and then in the first tab's controller, present the login controller modally from the viewDidAppear method, so it will appear right away (you will briefly see the first tab's view unless you uncheck the "animates" box in the segue's attributes inspector). Present the details controller from that one, and then dismiss both modal controllers to get back to your main content. When the user logs out, just present that login controller again. I implement this idea like this. In the first tab's view controller:
- (void)viewDidLoad {
[super viewDidLoad];
_appStarting = YES;
}
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if (_appStarting) {
[self performSegueWithIdentifier:#"Login" sender:self];
_appStarting = NO;
}
}
Then in the last (second in your case) modal view controller, I have a button method:
-(IBAction)goBackToMain:(id)sender {
[self.view.window.rootViewController dismissViewControllerAnimated:YES completion:nil];
}
Figured it out myself...just had to go up one more level to get to the "root" view controller (LogInViewController) and found that this did the trick:
[[self.presentingViewController presentingViewController] dismissViewControllerAnimated:YES completion:nil];
As I said I'm just getting the presentingViewController (DetailEntryViewController) and then going up one more level and getting that controller's presenter (LogInViewController).
I had similar problem and my "modal segue chain" was not limited. I agree with the arguments in the answer and comments below about modal segues designed for different thing, but I liked the "horizontal flip" animation of modal segues and I couldn't find the easier way to replicate them... Also in general I don't see anything wrong in using things that were designed for one thing to achieve some other thing, like chaining modal controllers. Repeated "partial curl" animation can also apply to some scenario in some app.
So I implemented the stack of modal controllers as a property of controller:
#interface ModalViewController : UIViewController
#property (nonatomic, retain) NSMutableArray *modalControllers;
#end
When the first modal segue is executed the stack is created in prepareForSegue method of controller that is not modal:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"modalSegue"]) {
ModalViewController *controller =
(ModalViewController *)[segue destinationViewController];
controller.modalControllers = [NSMutableArray arrayWithObject: controller];
}
}
When one modal controller moves to another the destination is added to the stack (in the method of ModalViewCotroller)
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"modalSegue"]) {
ModalViewController *destController =
(ModalViewController *)[segue destinationViewController];
// add destination controller to stack
destController.modalControllers = _modalControllers;
[destController.modalControllers addObject: destController];
}
}
To dismiss the whole stack at once was the most tricky part - you can't dismiss the previous controller before the next finished dismissing, so the cycle did not work, only recursive blocks did the trick, with avoiding the memory leak being the trickiest (I'm yet to check it, but I relied on this):
- (IBAction)dismissAllModalControllers: (id)sender
{
// recursive block that dismisses one auth controller
// all these dances are to avoid leaks with ARC
typedef void (^voidBlockType)();
__block void (^dismissController) ();
voidBlockType __weak dismissCopy = ^void(void) {
dismissController();
};
dismissController = ^void(void) {
int count = [_modalControllers count];
if (count > 0) {
// get last controller
UIViewController *controller =
(UIViewController *)[_modalControllers lastObject];
// remove last controller
[_modalControllers removeLastObject];
// dismiss last controller
[controller
// the first controller in chain is dismissed with animation
dismissViewControllerAnimated: count == 1 ? YES : NO
// on completion call the block that calls this block recursively
completion: dismissCopy];
}
};
// this call dismisses all modal controllers
dismissController();
}
[self.navigationController popToRootViewControllerAnimated:YES];