so basically in my app delegate i have a navigation.controller
This navigation controller has a view of a class named MainScreen.
In MainScreen.m , i have a IBAction which will bring me to a SelectionScreen.m page by pushing it. here is the coding for it
SelectionScreen *aSelectionScreenViewController = [[SelectionScreen alloc]initWithNibName:#"SelectionScreen" bundle:nil];
[self.navigationController pushViewController:aSelectionScreenViewController animated:YES];
[aSelectionScreenViewController release];
So how do i check if my current navigationController.view = this selectionscreen.view?
The reason for checking which current view it is, is because when i receieve a push notification, i would want to automatically switch to this SelectionScreen.m page and invoke some methods within it. But this checking can only be done in the appDelegate because the didReceiveRemoteNotification method is located in there.
This is how i'm doing it
for example if you have three ViewControllers ,and any of those have possibility to be pushed by NavigationController:
ViewControllerA
ViewControllerB
ViewControllerC
Then what you need to do is:
-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerA class]]) {
//do sth
}
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerB class]]) {
//do sth
}
if ([[self.navigationController topViewController] isKindOfClass:[ViewControllerC class]]) {
//do sth
}
}//end of code
One way is to save selectionScreenViewController as a property of your app delegate, then:
if (self.navigationController.topViewController == self.selectionScreenViewController) {
//...
}
else {
//...
}
Hey guys, i did it in a simple way. In every view controller i had, i removed all objects and assigned an object to an array in the appdelegate. So this way, everytime i go to a new view, the value is different.
So in appdidrecieveremotenotification, i can check that array and decide on what to do accordingly.
Its just a simple way of checking.
Related
I want to check the pasteboard and show an alert if it contains specific values when the view appears. I can place the code into viewDidLoad to ensure it's only invoked once, but the problem is that the alert view shows too quickly. I know I can set a timer to defer the alert's appearance, but it's not a good work-around I think.
I checked the question iOS 7 - Difference between viewDidLoad and viewDidAppear and found that there is one step for checking whether the view exists. So I wonder if there's any api for doing this?
Update: The "only once" means the lifetime of the view controller instance.
There is a standard, built-in method you can use for this.
Objective-C:
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if ([self isBeingPresented] || [self isMovingToParentViewController]) {
// Perform an action that will only be done once
}
}
Swift 3:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if self.isBeingPresented || self.isMovingToParentViewController {
// Perform an action that will only be done once
}
}
The call to isBeingPresented is true when a view controller is first being shown as a result of being shown modally. isMovingToParentViewController is true when a view controller is first being pushed onto the navigation stack. One of the two will be true the first time the view controller appears.
No need to deal with BOOL ivars or any other trick to track the first call.
rmaddy's answers is really good but it does not solve the problem when the view controller is the root view controller of a navigation controller and all other containers that do not pass these flags to its child view controller.
So such situations i find best to use a flag and consume it later on.
#interface SomeViewController()
{
BOOL isfirstAppeareanceExecutionDone;
}
#end
#implementation SomeViewController
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if(isfirstAppeareanceExecutionDone == NO) {
// Do your stuff
isfirstAppeareanceExecutionDone = YES;
}
}
#end
If I understand your question correctly, you can simply set a BOOL variable to recognize that viewDidAppear has already been called, ex:
- (void)viewDidAppear {
if (!self.viewHasBeenSet) { // <-- BOOL default value equals NO
// Perform whatever code you'd like to perform
// the first time viewDidAppear is called
self.viewHasBeenSet = YES;
}
}
This solution will call viewDidAppear only once throughout the life cycle of the app even if you create the multiple object of the view controller this won't be called after one time. Please refer to the rmaddy's answer above
You can either perform selector in viewDidLoad or you can use dispatch_once_t in you viewDidAppear. If you find a better solution then please do share with me. This is how I do the stuff.
- (void)viewDidLoad {
[super viewDidLoad];
[self performSelector:#selector(myMethod) withObject:nil afterDelay:2.0];
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
static dispatch_once_t once;
dispatch_once(&once, ^{
//your stuff
[self myMethod];
});
}
By reading other comments (and based on #rmaddy 's answer), I know this is not what OP asked for, but for those who come here because of title of the question:
extension UIViewController {
var isPresentingForFirstTime: Bool {
return isBeingPresented() || isMovingToParentViewController()
}
}
UPDATE
You should use this method in viewDidAppear and viewWillAppear. (thanks to #rmaddy)
UPDATE 2
This method only works with modally presented view controllers and pushed view controllers. it's not working with a childViewController. using didMoveToParentViewController would be better with childViewControllers.
You shouldn't have issues in nested view controllers with this check
extension UIViewController {
var isPresentingForFirstTime: Bool {
if let parent = parent {
return parent.isPresentingForFirstTime
}
return isBeingPresented || isMovingFromParent
}
}
Try to set a BOOL value, when the situation happens call it.
#interface AViewController : UIViewController
#property(nonatomic) BOOL doSomeStuff;
#end
#implementation AViewController
- (void) viewWillAppear:(BOOL)animated
{
if(doSomeStuff)
{
[self doSomeStuff];
doSomeStuff = NO;
}
}
in somewhere you init AViewController instance:
AddEventViewController *ad = [AddEventViewController new];
ad.doSomeStuff = YES;
Not sure why you do this in ViewDidAppear? But if you want doSomeStuff is private and soSomeStuff was called only once, here is another solution by notification:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(doSomeStuff) name:#"do_some_stuff" object:nil];
- (void) doSomeStuff
{}
Then post when somewhere:
[[NSNotificationCenter defaultCenter] postNotificationName:#"do_some_stuff" object:nil];
swift 5
I've tried isBeingPresented() or isMovingToParent.
But It doesn't work.
So I tried below code. and It's work for me!
override func viewDidAppear(_ animated: Bool) {
if (self.isViewLoaded) {
// run only once
}
}
You can use this function in ViewDidLoad method
performSelector:withObject:afterDelay:
it will call that function after delay. so you don't have to use any custom timer object.
and For once you can use
dispatch_once DCD block.Just performSelector in the dispatch_once block it will call performSelector only once when ViewDidLoad is called
Hope it helps
It looks like this topic comes up a lot. I read through several answers but none were the same case as mine so please excuse me if you've seen similar before.
All of my UIViewControllers are being controlled by UINavgationController. On the first UIViewController (SMOnboardingPhotoMarketingViewController), I call into my keychain wrapper class to see if there is anyone logged in (app resuming). If so I call the segue to go to my main logged in screen (SMThumbnailViewController), where I'm getting the error message: Unbalanced calls to begin/end appearance transitions for .
I have examined all of the view controller life-cycle calls to ensure that I'm calling [super method] if I over-rode them. Done.
Other than that this is just a standard push type segue for all transitions. I don't understand what is so different about this call to a segue than all the others that are triggered by button actions. Here is the code from my first view controller:
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
[self loadScrollViewContent];
__weak SMOnboardingPhotoMarketingViewController *weakSelf = self;
[SMAuthentication validateStoredTokenWithCompletion:^(BOOL valid) {
if(valid){
NSLog(#"Logged in. Continue to thumbs page");
[weakSelf performSegueWithIdentifier:kSeguePhotoMarketingToThumbnails sender:self];
}
else{
[SMAuthentication logOut];
NSLog(#"invalid credentials stored. User must log in ");
}
}];
}
I've noticed that in my main view controller (the one that the above code navigates to), viewDidLoad is called, but viewDidAppear is never called. What could cause such an imbalance?
Edit: Adding info. I should state taht if I move the segue call to the outside of that block, the transition goes as normal with no error. Example:
// I know this is ugly. It is for testing only
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
[self loadScrollViewContent];
__block BOOL complete = NO;
__block BOOL isValid = NO;
[SMAuthentication validateStoredTokenWithCompletion:^(BOOL valid) {
if(valid){
NSLog(#"Logged in. Continue to thumbs page");
isValid = YES;
}
else{
[SMAuthentication logOut];
NSLog(#"invalid tokens stored. User must log in ");
}
complete = YES;
}];
while (!complete) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
if(isValid){
[self performSegueWithIdentifier:kSeguePhotoMarketingToThumbnails sender:self];
}
}
You probably have implemented the following ViewController custom container methods:
- (void)endAppearanceTransition
- (void)beginAppearanceTransition:(BOOL)isAppearing animated:(BOOL)animated
I once written and forgot them in a base class and they messed up the whole appearance forwarding to child controllers when using storyboards.
Have two actionsheet buttons and one modalviewcontroller on mainviewcontroller in application. Now for two actionsheet buttons and for modalviewcontroller, can i have multiple dismissviewdidfinish method for each
-(void)dismissViewDidFinish:(ModalViewController *)controller
{
[self dismissModalViewControllerAnimated:YES];
}
-(void)dismissViewDidFinish:(Devanagari *)controller1;
{
[self dismissViewControllerAnimated:completion];
}
-(void)dismissViewDidFinish:(English *)controller2;
{
[self dismissViewControllerAnimated:YES];
}
Cause if i add these three methods on mainviewcontroller i get red warning message duplicate declaration of method dismissviewdidfinish.
Any ideas how to solve this kind of situation.
You cannot have the same name for more than 1 method. Use a single dismissViewDidFinish:(UIViewController *)viewController method and then check to see which viewController finished:
- (void)dismissViewDidFinish:(UIViewController *)viewController {
//check to see what kind of class viewController is
//or use tags by setting the viewcontroller.view.tag when creating it
}
I am playing around with the new iOS 5 features and trying to rewriting one of my apps as pure iOS 5 app using the new storyboarding feature.
To cut a long story short, I have a start screen where the app tries to connect to a server if the user saved some login data, if not, it should ask for them.
Here is how I would do it. I create a Viewcontroller which is doing the connection thing in the viewDidLoad method. If there is no login data or the login is not successful, I need a to do a manual segue to the login screen.
Now is this even possible, or do I need 2 story boards for that ?
I have solved it by putting a login view without any segues (to or from it) like in the screenshot below:
Then, I used a custom class in the tab bar controller to show it whenever I need it.
In the tab bar controller class, I use 'viewDidLoad' to fire up the login view. To show the modal view, I do have a singleton thingy that stores some state, say BOOL isAuthenticated, where I do the magic:
- (void) performLoginIfRequired: (UIViewController *) source {
if (!self.isAuthenticated) {
NSLog(#"Is not authed");
UIStoryboard *storyboard = [UIApplication sharedApplication].delegate.window.rootViewController.storyboard;
UIViewController *loginController = [storyboard instantiateViewControllerWithIdentifier:#"loginScreen"];
[source presentModalViewController:loginController animated:YES];
} else {
NSLog(#"Is authe");
}
}
And, in my case, I wanted it to be shown when the app first starts, but also when it enters foreground again. So, I registered my tab bar controller with the notification center, so I get notified if the app is coming back:
-(void)viewDidLoad {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(willEnterForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
}
In the willEnterForeground method, I do:
-(void) willEnterForeground: (NSNotification *)notification {
[[myStateThingy defaultState] performLoginIfRequired:self];
}
It sounds like you need to use the performSegueWithIdentifier method. Make sure both views are in the same storyboard, link them together using a Push segue, and give that segue a name. Then, from your first view controller's code simply call the performSegueWithIdentifier to perform a manual segue.
Hope this helps!
See also: Conditionally following a segue
Cheers,
Jesse L. Zamora
I had this same issue, and I solved it simply by doing the following: Instead of trying to segue to a login screen(modally or push), I made the login screen my root view controller. In the login view controller's viewWillAppear method, I check if someone's logged in already. If so, I push my home screen:
// mutableFetchResults is an array with my persistent Credentials object
if ([mutableFetchResults count] > 0) { // Someone's already logged in
[self performSegueWithIdentifier:#"Home" sender:self];
}
Also, in the Home screen view controller's viewWillAppear method, I hid the back button with this line, so the user can't go "back" to the login screen:
self.navigationItem.hidesBackButton = YES;
Finally, every page of my app has a "Sign Out" bar button on the top right. Signing out and putting the login screen up was as simple as this:
- (IBAction)signOutButtonPressed:(UIBarButtonItem *)sender {
MyAppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
[appDelegate signOutCurrentUser]; // this method in my app delegate deletes the current Credentials
[self.navigationController popToRootViewControllerAnimated:YES];
}
Hope that was simple enough!
After trying many different methods, I was able to solve this problem with this:
-(void)viewWillAppear:(BOOL)animated {
// Check if user is already logged in
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
if ([[prefs objectForKey:#"log"] intValue] == 1) {
self.view.hidden = YES;
}
}
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
// Check if user is already logged in
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
if ([[prefs objectForKey:#"log"] intValue] == 1) {
[self performSegueWithIdentifier:#"homeSeg3" sender:self];
}
}
-(void)viewDidUnload {
self.view.hidden = NO;
}
I am sure this is in the Apple documentation or must have been answered somewhere on this forum, since it seems so basic, but I could not find it nor a particularly elegant solution myself.
What I have is a UIViewController that pushes an editing view on its navigation stack. The editing view has a bunch of UITextFields in it. If one of them is being editing when the back button is touched, the original view's ViewWillAppear method is called before either the UITextField delegate methods of textFieldShouldEndEditing or textFieldDidEndEditing, or the IB linked action textFieldEditingEnded method are called.
Here is some code that I hope will make it clearer:
In the UIViewController:
- (void) viewWillAppear: (BOOL) animated {
[super viewWillAppear: animated];
NSLog( #"Entering view will appear for master view" );
nameLabelField.text = objectToEdit.name;
}
- (IBAction) editMyObject: (id) sender {
NSLog( #"Editing the object" );
EditViewController *evc = [[EditViewController alloc] initWithNibName: #"EditTableView" bundle: nil];
evc.editedObject = objectToEdit;
[self.navigationController pushViewController: evc animated: YES];
[evc release];
}
In the EditViewController <UITextFieldDelegate>:
- (void) viewWillAppear: (BOOL) animated {
[super viewWillAppear: animated];
nameField.text = editedObject.name;
}
- (void) viewWillDisappear: (BOOL) animated {
[super viewWillDisappear: animated];
NSLog( #"In viewWillDisappear" );
if( [self.navigationController.viewControllers indexOfObject: self] == NSNotFound ) {
NSLog( #"-- We are not in controller stack... the back button has been pushed" );
}
}
- (BOOL) textFieldShouldEndEditing: (UITextField *) textField {
NSLog( #"In textFieldShouldEndEditing" );
// Store text field value here???
// editedObject.name = nameField.text;
return YES;
}
- (void) textFieldDidEndEditing: (UITextField *) textField {
NSLog( #"In textFieldDidEndEditing" );
// Store text field value here???
// editedObject.name = nameField.text;
}
- (IBAction) textFieldEditingEnded: (id) sender {
NSLog( #"In textFieldEditingEnded" );
// Store text field value here???
// editedObject.name = nameField.text;
}
The log ends up with:
[...] Entering view will appear for master view
[...] Editing the object
[...] In viewWillDisappear
[...] -- We are not in controller stack... the back button has been pushed
[...] Entering view will appear for master view
[...] In textFieldShouldEndEditing
[...] In textFieldEditingEnded
[...] In textFieldDidEndEditing
I want to set self.editedObject.name = nameField.text before the label gets set in viewWillAppear for the UIViewController.
I thought about in the viewWillDisappear method for the EditViewController checking to see if any of my text fields are currently the first responder and if so getting their text and storing it, but this seems like such a kludge that will be a pain to maintain if I add or change text fields.
I can also implement the textFieldEditingChanged IB linked action to set the text in the edited object after every keystroke but this is also quite a bit of overhead since I have to figure out which text field I am in every keystroke (remember I only showed name but there are a whole bunch of them).
All I need is for the editing to be ended or to know the editing will be ended before viewWillAppear is called in the UIViewController so the nameFieldLabel is properly set.
OK, I figured out a simple solution after a lot of web-surfing, forum reading, and manual reading. It was, as I suspected, very simple, only one line of code added. In the viewWillDisappear method of the EditViewContorller I simply added:
[self.view.window endEditing: YES];
Now textFieldShouldEndEditing, textFieldEditingEnded, and textFieldDidEndEditing all get fired off before the viewWillAppear of the master view does.
So now the viewWillDisappear method looks like:
- (void) viewWillDisappear: (BOOL) animated {
[super viewWillDisappear: animated];
NSLog( #"In viewWillDisappear" );
// Force any text fields that might be being edited to end so the text is stored
[self.view.window endEditing: YES];
}
And the methods already in place to handle the 'Return' on the keyboard also handle the 'Back' button on the Navigation controller.
Thank you Aaron and Jeff for your assistance and helping me think this through.
Why not just create your own Back button with that logic in its action method?
I would think that from a UX perspective, you should display an alert to determine if the user wants to cancel the edit action they were in the middle of before exiting the current view.
By alerting the user, you can see if they hit the button by accident or if they did decide to leave the view, take the appropriate action.
// add this to the field(s) to be edited, selector will be called as the changes
// are being made... still difficult to handle a cancel, but should work
[objectToEdit addTarget:self action:#selector(updateNameField:)
forControlEvents:UIControlEventEditingChanged];
additional code here...
// the method called to update object from parent view
- (void)updateNameField:(id)sender {
<OBJECT TO UPDATE>.text = ((UITextField *)sender).text;
}