I'm trying to detect a shake on the iPhone device, so for what i've read I need to set my view controller as first responder on the viewDidAppear method. This method is supposed to be called automatically, but for some reason this method is never called. Only viewDidLoad is called.
this is my code (I put only the relevant parts):
BuildHouseViewController.h:
#interface BuildHouseViewController : UIViewController {
BuildHouseViewController.m:
- (void)viewDidLoad {
[super viewDidLoad];
[self.view becomeFirstResponder];}
-(void)viewDidAppear:(BOOL)animated{
[self becomeFirstResponder];
[super viewDidAppear:animated];}
-(BOOL)canBecomeFirstResponder {
return YES;}
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event{
NSLog(#"shake");
if ( event.subtype == UIEventSubtypeMotionShake )
{ }
if ( [super respondsToSelector:#selector(motionEnded:withEvent:)] )
[super motionEnded:motion withEvent:event];
}
I added breakpoints on the viewDidAppear method and it is never called. Shakes are never detected, I suppose it is because as this methods are never called, so the view controller can never become first responder. I don't understand why this is happening.
Any help will be appreciated.
Edit:
I call the view from another view using:
[self.view addSubview:nextScreen.view];
The view is displayed on screen
Thanks for the quick answers.
I've found something interesting. I tried loading the same view I'm having problems with in different ways and I'm getting different results
-As I said before if I call it from another view using:
[self.view addSubview:nextScreen.view];
viewDidLoad is never called and I cannot detect shakes.
-Now if I call it from the AppDelegate using:
[window addSubview:nextScreen.view];
viewDidLoad is called!! and I am able to detect shakes, however this solution is not possible, I should be able to call it from another view
-If I call it from another view using:
[self presentModalViewController:nextScreen animated:YES];
viewDidLoad is called!! However I don't want to use a modal view controller, but it appears to be the only solution to my problem, shakes are detected.
It is strange that the first method doesn't load the view correctly, is it a bug??
The [self becomeFirstResponder] and the like don't actually make that become the first responder. The method gets called when the view is going to become the first responder. So that's not doing what you think it is.
Secondly, the viewDidAppear will only be called when the view, well, did appear. Is it showing up on the screen? Where are you telling it to be displayed? You need to either add the view controller's view as a subview of another view, or pushed onto a navigation controller stack, or pushed as a modal view.
viewDidAppear:(BOOL)animated only gets called when the view is shown by UINavigationController or UITabBarController. If you add a view controller's view to a subview (such as a scrollview or what have you), it won't get called. You would think it would but you'd be wrong. Just got bit by this myself.
Further to #Genericrich's comments, you can manually call viewDidAppear after you put the subview in yourself.
[self.view addSubview:theViewController.view];
[theViewController viewDidAppear:FALSE];
This worked for me. Hope it helps someone else.
Related
I'm stuck! I can't see why viewWillAppear doesn't run in my code but viewDidLoad runs. If I understand it correctly viewDidLoad runs once on the first instance and viewWillAppear runs every time a view is added to the stack of views to display.
I see others have had this issue but some how their solutions of calling viewWillAppear directly causes my app to crash. Other solutions were related to Navigation Controller and pushingView's but thats not what i'm using either! What am I missing?
Thanks in advance for your help! :)
See below:
View Controller #1 - Currently being displayed on screen
-(IBAction)someButtonPressed:(id)sender{
NSLog(#"FirstViewController - someButtonPressed");
SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:#"SecondViewController" bundle:nil];
secondViewController.myLocation = self.myLocation;
secondViewController.myDatabase = self.myDatabase;
[self.view addSubview:secondViewController.view];
//[secondViewController viewWillAppear:YES];
}
SecondViewController:
- (void)viewWillAppear:(BOOL)animated {
NSLog(#"SecondViewController - viewWillAppear");
[super viewWillAppear:animated];
// updating ivars with data
}
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
NSLog(#"SecondViewController - viewDidLoad");
[super viewDidLoad];
}
If I understand it correctly viewDidLoad runs once on the first instance and viewWillAppear runs every time a view is added to the stack of views to display.
-viewDidLoad is called every time a UIViewController's view is loaded. That may be many times during a single controller's life as the view may be unloaded to free up memory when it is not visible and reloaded, triggering another call to -viewDidLoad, when needed.
-viewWillAppear: is called when a UIViewController's view becomes visible. However UIKit assumes that UIViewController's views will fill their window. Nesting UIViewControllers' views is an example of abusing UIViewControllers and will result in unexpected behavior. As you have seen.
See About Custom View Controllers in the View Controller Programming Guide for iOS:
Each custom view controller object you create is responsible for managing all of the views in a single view hierarchy. In iPhone applications, the views in a view hierarchy traditionally cover the entire screen, but in iPad applications they may cover only a portion of the screen. The one-to-one correspondence between a view controller and the views in its view hierarchy is the key design consideration. You should not use multiple custom view controllers to manage different portions of the same view hierarchy. Similarly, you should not use a single custom view controller object to manage multiple screens worth of content.
If you wrote a custom UIViewController Container you might have overwritten the following method, which leads to your described behavior.
- (BOOL)shouldAutomaticallyForwardAppearanceMethods{
return NO;
}
In this case you have to manually handle beginAppearanceTransition/endAppearanceTransition.
See Apples View Controller Containment article
viewWillAppear: is called when a view controller is displayed in one of the normal ways (e.g. by selecting a tab in a UITabBarController, by pushing onto a UINavigationController, by being popped back to in a UINavigationController, by being presented with presentModalViewController:animated, by being uncovered after dismissModalViewControllerAnimated:, etc). Just displaying a view with addSubview: does not call the method.
It is possible to correctly call viewWillAppear: manually, but in general it's better to use one of the normal ways mentioned above.
Just try this.. I got it working :)
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
NSLog(#"SecondViewController - viewWillAppear");
// updating ivars with data
}
When you push view or present a view controller by pushViewController:animated or presentModelViewController:animated:, they will call viewWillAppear:animated:, and else method for you. But if you addSubview: manually, you need to call those method by self.
In a UIViewController subclass, I have the following methods:
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// do something
myTextField.text = #"Default";
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
// do something
[myTextField selectAll:self];
[myTextField becomeFirstResponder];
}
- (void)viewDidLoad {
[super viewDidLoad];
// do something
myTextField.delegate = self;
}
The NIB has been created using Interface Builder. The corresponding view controller object is pushed by the navigation controller through pushViewController.
The inteded behavior is to show a default text entry in a text field, to select the entire text and to set the text field as first responder. [Edit: I've noticed that selecting all and making first responder makes no sense as the selection would dissapear; still, I wonder why the methods behave as described next.]
However, while methods viewDidLoad and viewWillAppear are called, the method viewDidAppear is not called. Can anybody tell me why? Most questions I found on the web and here deal with both viewWillAppear/viewDidAppear are not working; I also understood that in subviews or programmatically created views these methods are not evoked; but this does not apply in case and also I wonder why one of these "lifecycle" methods is evoked and the other not.
Any idea? Thanks!
I had this issue happen to me: viewWillAppear was being called but viewDidAppear was not!
I finally figured out that this was because I had a tabBarController where I overloaded it's own viewDidAppear and forgot the [super viewDidAppear:animated];
It threw off every VC in every tab! adding that line back in fixed it for my other VC's.
Hope this helps someone!
There is one case when viewWillAppear will be called but viewDidAppear will not.
Suppose you have two viewControllers and you push from the first to the second controller. Then, using the swipe, you want to go back to the first one, both controllers are displayed at the same time and at that moment viewWillAppear will be called from the first controller.
This way, you do not finish the swipe and stay on the second controller and viewDidAppear will not be called from the first controller.
I had the same problem.
I had copy/pasted viewDidAppear to create viewWillAppear but had forgotten to change the super.viewDidAppear() call. This then seemed to stop viewDidAppear from being called.
It sounds like somewhere in your code you have missed or messed-up a call to the superclass.
The call to viewDidAppear: should always follow viewWillAppear: unless you are doing something custom, which you say you don't. I don't know why it doesn't work but here are a few ideas:
Could it be that you are doing something strange in one of the delegate methods for UITextFieldDelegate? It's unlikely that it would affect viewDidAppear: being called but it could be a culprit.
Have you loaded a lot of stuff into memory before pushing the view? I'm not sure what would happen if you got a memory warning between viewWillAppear: and viewDidAppear:.
Have you tried to do a Clean? Sometimes that can help.
In cases like these when it should work I usually create a new class and the introduce the functionality one at a the time to see if I can get it work that way. I tried your code in a new Navigation Based project where I added a new UIViewController with an outlet to the text field. Then I pasted the code from the question and it did work as expected.
This can be because you added a child view controller to your parent VC in viewDidLoad or viewWillAppear. The child's appearance prevents the call to viewDidAppear.
This is a crazy thing to do, and I only know because this was a bug in my code. I meant to add the child VC to this VC, not the parent VC.
I have a UINavigationController with a UITableView as my main menu. User clicks on a cell and a new view is pushed on the stack. In one case I push another UITableView that needs a toolbar. So on that 2nd tableView's init I setup the self.toolbarItems property with the correct items. But then I need to call [self.navigationController setToolbarHidden:NO animated:YES]; So it makes sense to call this in the viewDidAppear or viewWillAppear method. But I put it in those methods and find out (Also via NSLog) that they never get called. The same goes for hiding it in viewWillDisappear or viewDidDisappear. Why don't these methods get called? Where should I be doing this hiding/showing of the toolbar then?
I have noticed behavior where if a parent controller (like UINavigationController or UITabBarController) never get's viewWill/DidAppear called on it, it won't call it on the child controllers either. So make sure that in the code where you create the parent controller, you call viewWillAppear, show it, then call viewDidAppear. Then it should make those calls on it's child controllers as is appropriate.
Double check the parent controller is having those methods called, and call them yourself if they are not.
Yes Its true
you can do this by first write this code in
- (void)viewDidLoad {
self.navigationController.delegate = self;
}
And then write the code which you want to write in viewWillAppear
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
if ([viewController isKindOfClass:[self class]]) {
//write your code here
}
}
Although you solved your problem, in case someone comes along in the future another problem could have been that you forgot the animated: argument to either method - that is to say, the format of the method needs to look like:
- (void) viewWillAppear:(BOOL)animated
i noticed the same issue in iOS7. When i'm using both tab bar (2 buttons A, B) and navigation controller.
A has two views. One with tableview and second displays data according to the selection from the table view.
B has is the only view.
Button which is refer to another separate view D, placed in both tab bar views (A & B) and in both views of A.
Problem arises when i click the button from tab item B, viewWillAppear and viewDidLoad not called.
So i solved this issue by presentModalViewController:animated: and to come back i used dismissModalViewControllerAnimated:, just when i go to view D from tab item B.
I have an application where I was using buttons on a toolbar to call up the views, but I am switching it over to using a tab bar.
When using the buttons I was using the following code in MainViewController.m to update the values on the page and it was working just fine:
-(IBAction) loadSummaryView:(id) sender {
[self clearView];
[self.view insertSubview:summaryViewController.view atIndex:0];
//Update the values on the Summary view
[summaryViewController updateSummaryData];
[summaryViewController calculateData];
}
However, with the Tab Bar I can not figure out how to do this. I tried putting all of the necessary code in the Summary Views viewDidLoad and it loads the initial values, but it will not update the values when I change them in another view.
Any help is appreciated. I am a bit new at this, so please don't be cryptic as I may not understand the response.
Thank you.
By placing your code in viewDidLoad, it will only be called when the view is loaded from the nib. Unless you're running low on memory, this view will remain loaded for the duration of the life of your app.
So if you need to update values every time the view will appear, consider moving that code to an override of viewWillAppear
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// your stuff goes here...
[self updateSummaryData];
[self calculateData];
}
You can update your current view in the viewWillAppear:animated message of the view:
If you have everything setup correctly, there is nothing to do, the UITabBarController will show your view, an your UIViewController will receive a viewWillAppear message, where you can do your update:
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self updateSummaryData];
[self calculateData];
}
I strongly recommend reading the View Controller Programming Guide for iOS which describes in detail the main interface paradigms supported by the iPhone.
I wrote simple code to test UIImagePickerController:
#implementation ProfileEditViewController
- (void)viewDidLoad {
[super viewDidLoad];
photoTaker_ = [[UIImagePickerController alloc] init];
photoTaker_.delegate = self;
photoTaker_.sourceType = UIImagePickerControllerSourceTypeCamera;
photoTaker_.showsCameraControls = NO;
}
- (void)viewDidAppear: (BOOL)animated {
[self presentModalViewController: photoTaker_ animated: NO];
}
#end
And I'm getting strange warnings like the following:
2010-05-20 17:53:13.838 TestProj[2814:307] Using two-stage rotation animation. To use the smoother single-stage animation, this application must remove two-stage method implementations.
2010-05-20 17:53:13.849 TestProj[2814:307] Using two-stage rotation animation is not supported when rotating more than one view controller or view controllers not the window delegate
Got any idea what this is about? Thanks a lot in advance!
This message will appear if you are presenting the UIImagePickerController within another UIViewController. Because it isn't pushed like a UINavigationController stack, there is confusion at the UIWindow level. I don't know if the warning is a problem, but to eliminate the warning you can do the following:
// self = a UIViewController
//
- (void) showCamera
{
cameraView = [[UIImagePickerController alloc] init];
[[[UIApplication sharedApplication] keyWindow] setRootViewController:cameraView];
[self presentModalViewController:cameraView animated:NO];
}
- (void) removeCamera
{
[[[UIApplication sharedApplication] keyWindow] setRootViewController:self];
[self dismissModalViewControllerAnimated:NO];
[cameraView release];
}
Perhaps you are adding the root UIViewController's view as a subview of the window instead of assigning the view controller to the window's rootController property?
IT ALL FALLS BACK ON THE UI
This warning can be implemented for several different objects: Pickers, keyboard, etc.
I have found that it is related to the UI taking two steps to complete a transition or other animation. Or for any instance where the UI is trying to finish one thing and is being asked to execute another before it has finished. (therefore it covers a wide range of possible triggers)
I have seen the warning appear on 4.0 & 4.2. In my case I was working with rotating the device and catching whether the keyboard was still up-(i.e. text field was still first responder). If so, the keyboard needed to stay up for between the views, but this presented other complications with other views.
Therefore, I implemented a BOOL tracker to keep track if keybaordIsPresent, and if so I was {textfield resignFirstResponder]; when detecting the orientation change and the reset the textfield to becomeFristResponder after the transition that was wrapped in an Animation Block. My BOOL tracker worked better, I still use the NSNotifications for the Keyboard, but there were overlaps of notifications during rotations because the keyboard was being dismissed without requesting such. The BOOL is set to NO on Load, and when the [textfield resignFirstResponder]; is implemented. *not when "-(void)keyboardWillhide is trigger by the NSNotifications, which gives me both working triggers that never conflict. The BOOL is set to YES, only when the user touches textfield which automatically triggers becomeFirstResponder.
I removed the warning by taking the [textfild resignFirstResponder]; out of the
-(void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
//if (keyboardIsPresent == YES) {[self.entryTextField resignFirstResponder];}
}
and placing it back at the top of the code for the:
- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
if (keyboardIsPresent == YES) {
[self.entryTextField resignFirstResponder];
}
//Determine Which Orientation is Present:
if((fromInterfaceOrientation == UIInterfaceOrientationPortrait) || (fromInterfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)){
//LANDSCAPE VIEW:
[self configureLandscapeView];
}else {
//PORTRAIT VIEW:
[self configurePortraitView];
}
}
**Even though I had no code inside the -(void)willAnimatFirstHalfOfRotationToInterface:, the warning was still popping up. I think the warning was still popping up because the compiler still has to attempt the method while it is trying to execute the first animation and therefore gets the double animation call or overlap of resources. It doesn't know that there is no executable code with the method until after it runs through it. And by that time it already set aside resource in preparation for handling possible actions within the method.
**To ellimiate the warning I had to remove or nil out the code for the willAnimateFirstHalfOfRotation, so that the compiler does not have to even check to see if there is a possible 2nd animation or action that may need to be executed at the same time.
/*-(void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
//if (keyboardIsPresent == YES) {[self.entryTextField resignFirstResponder];}}*/
After the transition is completed, within the original animation block I check to see if the "keyboardIsPresent" was YES prior to the rotation, and if so, I resign the First Responder once again. I use setAnimationDuration:0.3which comes out pretty clean and not jumpy.
Well, you are presenting UIImagePickerController modally inside viewDidAppear of ProfileEditViewController.
Think about this. That means when ProfileEditViewController view appears, the UIImagePickerController appears, say later you dismiss UIImagePickerController and it goes back to ProfileEditViewController, then viewDidAppear is called again and UIImagePickerController appears, say later you dismiss UIImagePickerController and it goes back to ProfileEditViewController, then viewDidAppear is called again and.... you get the idea.
That warning is rather cryptic though, not sure if that is what it's trying to tell you. I would suggest making a button somewhere on the ProfileEditViewController that calls presentModalViewController and also make sure you have a way to dismiss the UIImagePickerController (I've never used it not sure if it has one automatically).
You may be trying to present two modal view controllers at the same time, and they are fighting for animation resources.
1) There is rarely any UI reason to do this. You could instead just go directly to the second view controller (the image picker); and, after dismissing it, then present the first view or view controller.
2) If you do want two stacked view controllers or a view controller on top of a view, then set a timer in viewDidAppear to present the second view controller after the first one has finished it's animation. (You could display a dummy png image of a blank picker in the first one to prevent too much display flashing until the second view controller goes live.)
EDIT - Added a random code example:
I might try substituting this as an experiment:
- (void)foo {
[self presentModalViewController: photoTaker_ animated: NO];
}
- (void)viewDidAppear: (BOOL)animated {
NSTimer *bar = [ NSTimer scheduledTimerWithTimeInterval: (2.0f)
target: self
selector: #selector(foo)
userInfo: nil
repeats:NO ];
}
A shorter time delay may work as well.
I just had the same problem. In my case was a silly mistake that I'm putting here just in case anyone else falls into that same issue.
In my tabbed app I remove one of the original ViewControllers and added a new one with Storyboard to create a "Settings" section.
This new VC had to be a table view VC and even I designed, compiled and run it without a problem, when I changed the orientation of the app I kept getting this “Using two-stage rotation animation” error.
My problem was that I forgot to change in the original .h file interface "UIViewController" for "UITableViewController".
Once this was done I changed on the Storyboard identity badge the class from the general value to my SettingsViewController and that was the end of it.
I hope it can help someone else. It took me a while to get to bottom of this.
Cheers,
I think the warning here is about Core Animation performance. As a test, I loaded the image picker without any action sheet or other animations going on and the warnings are still there. I think these are warnings coming from the image picker class itself and not from any misuse of the API.