I have a project in xcode that uses storyboards. The first view that loads is an "accept terms and conditions" view in which the user must click an accept button to proceed. After clicking it, it segues to the next view. After the user clicks accept the first time the program launches, I never want them to see that view again - I want it to go straight to the next view. I have some code but its not working. Here is what I have exactly:
In app delegate: (inside applicationDidFinishLaunchingWithOptions)
if([[NSUserDefaults standardUserDefaults] boolForKey:#"TermsAccepted"]!=YES)
{
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:#"TermsAccepted"];
}
Inside the accept terms and conditions view implementation: (viewDidLoad)
if ([[NSUserDefaults standardUserDefaults] boolForKey:#"TermsAccepted"]){
[self.navigationController pushViewController: self animated:YES];
//I want it to go to the next screen
}
else {
//I want to show this screen, but I don't know what goes here
}
Also Inside the accept terms and conditions view implementation (in the accept button)
- (IBAction)acceptButton:(id)sender {
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:#"TermsAccepted"];
}
I run it and get the error: 'Pushing the same view controller instance more than once is not supported'. How do I fix this?
In your first code snippet, you basically say "if TermsAccepted is not YES (so it is NO), then set it to NO. This does not make sense
In your 2nd code snippet, you wrote [self.navigationController pushViewController:self animated:YES];. So basically you ask the current UIViewController (self) to push itself on its own navigationController… which does not make sense either.
That's why you have this error. You try to push the current viewController self whereas it is already on screen in your navigationController. So you try to push the same instance (self) twice on the same navigationController.
You obviously meant to push another viewController (probably an instance of a TermsAndConditionViewController or something that shows the terms and conditions of your app) on the navigation controller, and not the current viewController itself, which doesn't make sense.
First, you want to have the next view controller, the one you always want to show, be the root view controller of your window. In that controller's viewDidLoad method, put your if clause to show the accept terms and conditions controller -- you can show that one using presentModalViewController. The if clase can be like this:
If([[NSUserDefaults standardUserDefaults] BoolForKey:#"TermsAccepted"] !=YES) {
// instantiate your terms and conditions controller here
// present the controller
}
Then, in the method where you dismiss the terms and conditions controller, set the value of that key to YES.
Related
I have an app that has an initial login screen then when the user wants to sign up, they are presented with a registration form that is three view controllers presented modally. When the user completes the form on the third screen (by pressing a "Done" button), I want the user to be taken back to the initial login screen.
I have tried doing this in the third view controller:
[self dismissViewControllerAnimated:NO completion:nil]
[self.presentingViewController dismissViewControllerAnimated:NO completion:nil]
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:NO completion:nil]
However it only dismissed two of the view controllers and not all 3. Why did this happen?
As other people pointed out, there are more elegant/efficient/easier ways to achieve similar results from the UX perspective: via a navigation controller, or a page view controller, or other container.
Short/quick answer: you need to go one step further in the chain of presenting view controllers, because the dismissal request needs to be sent to the controller that's presenting, and not to the one that's being presented. And you can send the dismiss request to that controller only, it will take care of popping from the stack the child controllers.
UIViewController *ctrl = self.presentingViewController.presentingViewController.presentingViewController;
[ctrl dismissViewControllerAnimated:NO completion:nil]
To explain why, and hopefully help other people better understand the controller presenting logic in iOS, below you can find are more details.
Let's start from Apple documentation on dismissViewControllerAnimated:completion:
Dismisses the view controller that was presented modally by the view controller.
The presenting view controller is responsible for dismissing the view controller it presented. If you call this method on the presented view controller itself, UIKit asks the presenting view controller to handle the dismissal.
Thus [self dismissViewControllerAnimated:NO completion:nil] simply forwarded the request to self.presentingViewController. Which means the first two lines had the same effect (actually the 2nd line did nothing as there was no presented controller after the 1st one executed).
This is why your dismissal of view controllers worked only the top 2 ones. You should've start with self.presentingViewController and go along the chain of presenting view controllers. But this is not very elegant and can cause problems if later on the hierarchy of view controllers changes.
Continuing to read on the documentation, we stumble upon this:
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.
So you needn't call dismissViewControllerAnimated:completion: three times, a call on the controller that you want to come back will suffice. At this point, passing a reference to that controller would be more reliable than navigating through the stack of view controllers.
There are some more useful details in the documentation, for example regarding what transitions apply when dismissing multiple controllers at once.
I recommend you go through the whole documentation, not only for this method, but for all methods/classes that you use in your application. You'll likely discover things that will make your life easier.
And if you don't have the time to read all Apple's documentation on UIKit, you can read it when you run into problems, like in this case with dismissViewControllerAnimated:completion: not working as you thought it would.
As a closing note, there are some more subtle issues with your approach, as the actual dismissal takes place in another runloop cycle, as it's possible to generate console warnings and not behave as expected. This is why further actions regarding presenting/dismissing other controllers should be done in the completion block, to give a change to UIKit to finish updating its internal state.
Totally understood. What I will do is embed a navigation controller instead of using modal. I have a case just like you. I have LoginViewController to be the root view controller of the UINavigationController. SignupViewController will be presented by push method. For ResetPasswordViewController, I will use modal because it's supposed to go back to LoginViewController no matter the results. Then, you can dismiss the whole UINavigationController from SignupViewController or LoginViewController.
Second approach will be like, you come up with your own mechanism to reference the presented UIViewController via a shared instance. Then, you can easily dismiss it. Be careful with the memory management. After dismissing it, you should consider whether you need to nil it right away.
I know three ways to dismiss several viewControllers:
Use a chain of completion blocks
~
UIViewController *theVC = self.presentingViewController;
UIViewController *theOtherVC = theVC.presentingViewController;
[self dismissViewControllerAnimated:NO
completion:^
{
[theVC dismissViewControllerAnimated:NO
completion:^
{
[theOtherVC dismissViewControllerAnimated:NO completion:nil];
}];
}];
Use 'viewWillAppear:' method of viewControllers
~
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (self.shouldDismiss)
{
CustomVC *theVC = (id)self.presentingViewController;
theVC.shouldDismiss = YES;
[self dismissViewControllerAnimated:NO completion:nil];
}
}
Pass a reference to LoginVC1 further down the chain.
(This is the best approach so far)
Imagine you have some StandardVC, which presented LoginVC1.
Then, LoginVC1 presented LoginVC2.
Then, LoginVC2 presented LoginVC3.
An easy way of doing what you want would be to call (from inside your LoginVC3.m file)
[myLoginVC1 dismissViewControllerAnimated:YES completion:nil];
In this case your LoginVC1 would lose its strong reference (from StandardVC), which means that both LoginVC2 and LoginVC3 would also be deallocated.
So, all you need to do is let your LoginVC3 know that LoginVC1 exists.
If you don't want to pass a reference of LoginVC1, you can use:
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:NO completion:nil];
However, the above approaches are NOT the correct ways of doing what you want to do.
I would recommend you doing the following:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
if (!self.isUserLoggedIn)
{
[UIApplication sharedApplication].keyWindow.rootViewController = self.myLoginVC;
}
return YES;
}
Then, when user finished his login process, you can use
[UIApplication sharedApplication].keyWindow.rootViewController = self.myUsualStartVC;
I have a the first application controller, MAViewControllerMenu, and when that controller loads, I already allocate the next controller, imageControllerView.
- (void)viewDidAppear{
[super viewDidAppear:(YES)];
if (!imageControllerView)
imageControllerView = [[self storyboard] instantiateViewControllerWithIdentifier:#"chosenImageController"];
}
Then, I select an image from the image picker, and want to move to the next controller,imageControllerView, where the image would be displayed. I set the next window's image property as follows:
imageControllerView.image = [[self.pageViews objectAtIndex:(centered_image_ind)] image];
This line works, I checked that there's a value in imageControllerView.image.
However, when I move to the next controller,imageControllerView , I notice that the memory address of imageControllerView changes, or in other words, imageControllerView's properties that I change before moving to that controller, specifically image, reset when I move there.
Instead of throwing code here, I was hoping you could let me know what I should provide.
I think it's a common problem people know of:
Controller's objects re-init'ing when moving from one controller to another.
Here's a screen shot that might give a hint of what Im trying to do
Left most one is where I select pictures which in turn go into the slide show scrollview. Then I click next, and the image is supposed to appear in the centered ImageView
Thanks
OK...
You cannot "already allocate the next view controller" this won't work. There is no point in creating it like this at all. You can delete the imageViewController property (or iVar) completely.
The arrows that you have between the view controllers in your storyboard are segues. In Interface Builder you can select a segue and give it an identifier. For instance you would use something like #"ImageViewSegue".
I guess the segue is attached to the Next button. This is fine.
Now, in your MAViewControllerMenu you need to put this method...
- (void)prepareForSegue:(UIStoryBoardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"ImageViewSegue"]) {
// the controller is CREATED by the segue.
// the one you create in view did load is never used
ImageViewController *controller = segue.destinationController;
controller.image = [[self.pageViews objectAtIndex:(centered_image_ind)] image];
}
}
Now for the segues in the other direction...
You appear to be using segues to dismiss the modal views. You can't do this. What it will do is create a new view controller and present that instead of dismissing the presented view.
i.e. you'll go...
A -> B -> C -> B -> A -> B
// you'll now have 6 view controllers in memory
// each segue will create a fresh view controller with no values set.
What you want is...
A -> B -> C
A -> B
A
// now you only have one view controller because the others were dismissed.
// when you dismiss a view controller it will go back to the original one.
// the original one will have all the values you set previously.
To do this you need to create a method something like...
- (IBAction)dismissView
{
[self dismissViewControllerAnimated:YES completion:nil];
}
Then whatever the button is for your dismiss action attach it to this method.
Now delete all the backwards curly segues.
Passing info back
To pass info back to the original view controller you need a delegation pattern or something similar.
You can read more about creating a delegate at This random Google Search
Create a delegate method something like...
- (void)imageViewSelectedImage:(UIImage *)image;
or something like this.
Now when you do prepareForSegue you can do...
controller.delegate = self;
and have a method...
- (void)imageViewSelectedImage:(UIImage *)image
{
// save the method that has been sent back into an array or something
}
I might be wrong, but seems you go to your second view controller using a segue, it is normal your controller instance isn't the same than the one retrieved by [[self storyboard] instantiateViewControllerWithIdentifier:#"chosenImageController"]
you should take a look at - (void) prepareForSegue:(UIStoryboardSegue *)segue
(UIViewController method)
inside this method set your image property to the segue destination controller (check the identifier of the segue)
I have a basic ui navigation view with a table view, when a user selects a name and presses the top bar next button it should go to the main ui navigation view, after this initial setup it should start on the main view controller what's the best way to go about this?....
I currently have this:
My end goal is on complete of the LoginNavController it would "push" to the new NavController and on open always go straight too the new NavController. How do I do this in a efficient (and proper?) way?
I'm not sure what you mean with
My end goal is on complete of the LoginNavController it would "push" to the new NavController and on open always go straight too the new NavController. How do I do this in a efficient (and proper?) way?
If what you mean is that you would like to show the login view only once, and then always show the other view controller, one possible solution would be to use a modal segue to the next navigation controller (identified by the ID modalSegue in my code snippet). Once the login view controller has achieved its goal, you could save it through the use of NSUserDefaults (these are persistent between app launches). In the viewWillAppear method of the login view controller you could then check the value for the relative key, and if it is set then perform directly the segue to the other navigation view controller. It would be something like:
-(void)viewWillAppear:(BOOL)animated
{
NSNumber* result = [[NSUserDefaults standardUserDefaults] valueForKey:#"isSet"];
if(result.boolValue)
[self performSegueWithIdentifier:#"modalSegue" sender:self];
}
And to set the key once the loginViewController is done you would do something like:
-(void) setLoginCompleted
{
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:#"isSet"];
}
EDIT: For a smoother user experience, you could directly set the rootViewController of your application window in the didFinishLaunchingWithOptions: delegate's method. In this case you would do something like:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
MyNavController *nav = [self.window.rootViewController.storyboard instantiateViewControllerWithIdentifier:#"myNavVC"];
NSNumber* result = [[NSUserDefaults standardUserDefaults] valueForKey:#"isSet"];
if(result.boolValue)
[self.window setRootViewController:nav];
return YES;
}
In a project I'm writing I get this error when I present a new view controller:
Attempt to present.... while a presentation is in progress!
I think it happens because I first present a new view controller, and then in that view I present another view controller.
- (void)loadLabelSettings {
LabelSettingsViewController *labelSettings =
[[LabelSettingsViewController alloc] init];
labelSettings.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentViewController:labelSettings animated:YES completion:nil];
}
The program doesn't crash or anything it runs just fine, and there is no errors or warnings in my code. So my question is: Is it something I should be concerned with and if yes how do I solve it?
Thanks in advance :)
It is, like you said, probably caused by presenting two view controllers at the same time. Wait with presenting the second view controller until the first one has been fully presented. A good location would be to do this in viewDidAppear.
In my case, I connected a UIViewControllers UIButton with a second UIViewController by a UIStoryboardSegue. Inside my code a called it a second time programmatically. So pressing the UIButton caused presenting the specified view two times.
I figured out my problem, as Scott wrote it was because I was presenting 2 view controllers at the same time. It happened because I had a button that had a UILongPressGestureRecognizer, that showed the new view controller. The problem was that when using a UILongPressGestureRecognizer, the method that is being called, is called twice. First when the long press is detected and when your finger is released from the screen. So the presentViewController method of the same view, was called twice. I fixed this by only reacting to the first detection. Here is the code :
- (void)loadButtonSettings:(UILongPressGestureRecognizer *)recognizer {
if (recognizer.state == UIGestureRecognizerStateBegan) {
}
}
I have a problem in my application. Any help will be greatly appreciated. Basically it is from view A to view B, and then come back from view B.
In the view A, it has dynamic data loaded in from the database, and display on the table view. In this page, it also has the edit button, not on the navigation bar. When user tabs the edit button, it goes to the view B, which shows the pick view. And user can make any changes in here. Once that is done, user tabs the back button on the navigation bar, it saves the changes into the NSUserDefaults, goes back to the view A by pop the view B.
When coming back to the view A, it should get the new data from the UIUserDefaults, and it did. I used NSLog to print out to the console and it shows the correct data. Also it should invoke the viewWillAppear: method to get the new data for the table view, but it didn't. It even did not call the tableView:numberOfRowsInSection: method. I placed a NSLog statement inside this method but didn't print out in the console.
As the result, the view A still has the old data. the only way to get the new data in the view A is to stop and start the application.
Both view A and view B are the subclass of UIViewController, with UITableViewDelegate and UITableViewDataSource.
Here is my code in the view A :
- (void)viewWillAppear:(BOOL)animated {
NSLog(#"enter in Schedule2ViewController ...");
// load in data from database, and store into NSArray object
//[self.theTableView reloadData];
[self.theTableView setNeedsDisplay];
//[self.theTableView setNeedsLayout];
}
In here, the "theTableView" is a UITableView variable. And I try all three cases of "reloadData", "setNeedsDisplay", and "setNeedsLayout", but didn't seem to work.
In the view B, here is the method corresponding to the back button on the navigation bar.
- (void)viewDidLoad {
UIBarButtonItem *saveButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSave target:self action:#selector(savePreference)];
self.navigationItem.leftBarButtonItem = saveButton;
[saveButton release];
}
- (IBAction) savePreference {
NSLog(#"save preference.");
// save data into the NSUSerDefaults
[self.navigationController popViewControllerAnimated:YES];
}
Am I doing in the right way? Or is there anything that I missed?
When a view is first loaded, it calls the viewDidLoad method. If you create a stack, drill down into it (from A to B) and then return (B to A) the viewDidLoad does not get called again on A. What you may want to try is passing A into B (by passing in self) and call the viewDidLoad method to get the new data and then reloadData method on the the tableView to refill the table view.
What you may want to try is taking the data fetching and setting functionality out of the viewDidLoad method and place it in its own getData method. At the end of the getData method, you could place a [self.tableView reloadData]; to reset/refill the table view. From class B, you could call [self getData] and minimize the amount of work you would do in class B. This would help increase reuse-ability of that code and may prevent side effects from calling the viewDidLoad method.
You could also use viewDidAppear. It is called every time the screen appears. For performance reasons, set a flag so you don't repeat the same functionality in viewDidLoad with viewDidAppear for the first screen view.