I have code inside my viewWillAppear method that requires checking the tab bar's selectedIndex. The only problem is, at this point its too early for the program to return the index, so I'm getting null.
Is there a way to access the selectedIndex without having to put the code inside viewDidAppear? I'm trying to resolve a visible 1 second flicker/delay load, which seems to only work in viewWillAppear.
You have two ways to get it that I can think of. First, make the tabBarController a property of the appDelegate, and you can then get the appDelegate reference from the sharedApplication, then ask it for the UITabBarController object and ask it directly (or add a method to your appDelegate to provide the selectedIndex).
The second idea is to have a property on your viewController, just before its pushed (whatever) the selectedIndex is set.
Related
I am trying to use a variable (birthDateLabel) in two view controllers that are separated via a modal but use the same view controller class (CreateAccountViewController). The label works in the view that it is set in but after [self dismissViewControllerAnimated:YES completion:nil]; is run the varriable is reset, how can I retain it?
Order of operations:
The first instance of CreateAccountViewController is run
A button is tapped to go to a new instance of CreateAccountViewController but this instance has a different view with a UIDatePicker to set the birthDateLabel variable.
The birthDateLabel is set
The user taps done and dismissViewControllerAnimated is run
The app updates a UILabel on the first instance of CreateAccountViewController
Step 5 is what does not work, if I put the label on the view as the picker it works but when the modal is dismissed the variable is reset. How can I keep the variable set after the modal is dismissed? Or is my only option to create separate view controller classes?
I tried to do my best explaining this, but if you need me to explain it more just comment.
The standard way to do this is to use a delegate. The fact that your two controllers are both instances of the same class doesn't make any difference, other than they will both have a variable called birthDataLabel. The value of that variable is specific to each instance, just as it would be if these were of two different classes.
So, you should do it the right way, which is to create a delegate protocol in your second instance, and have the first one set itself as the delegate when it first presents the second one.
#rdelmar provides the most technically correct answer, but if it's just one value you could simply use nsuserdefaults. If the number begins to expand creating a delegate might be a smart choice.
The structure of my MainStoryboard is:
->Tab Bar Controller -> Navigation Controller -> View Controller (Search)
The behaviour I want to have is that when the user re-selects the Search tab, the UIScrollView on it scrolls to the top. I am unsure how to get the event from the TabBarController, however.
I've been looking at a lot of stuff about UITabBarDelegate, particularly:
- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
I have, not quite managed to get this to work properly though. I am very unsure about how to go about setting the delegate (assuming that is the way it's done). I've tried hooking it up in IB, but it wouldn't let me. I also tried to get the UITabBar from the AppDelegate (after looking at some seemingly-related answers).
Any pointers will be greatly appreciated (unless they're null).
UITabBar *aTabBar = [UITabBarItem alloc] init];
....Any other modifications you want to make to aTabBar....
[aTabBar setDelegate:self]
Don't forget to add "<UITabBarDelegate>" to the "#interface" part of whatever object you're trying to designate as the delegate.
For my own code, I usually use some object that isn't the application delegate (as the app delegate is usually meant for application level events like "application is suspending" or "application is coming back into foreground"). If you add "<UITabBarDelegate>" to your Search view controller, make sure that whatever you do with the "didSelectItem" method is applicable only to the Search view controller. Otherwise instantiate some different object if you want to do actions on various view controllers based on which tab bar item is being displayed.
Not sure how to ask this question so it will makes sense, but let me try. My app opens a UIViewController, and then calls another one. When it opens the other one it places a variable in a textfield successfully. When the user closes the 2nd UIViewController and returns to the 1st UIViewController, I pass back the variable and place it in a textfield. This is all successful at this point. The variable is being passed back and forth with no problems.
So here is what I am trying to do: upon returning to the 1st UIViewController I run a query statement which uses the variable in the textfield as a key to pull a record from a SQLite table. I use the NSLog to check the code and I see that the textfield is empty, but when the UIViewController appears the variable is in the textfield.
Are with me so far? I hope so…
I am running the query in the ViewDidLoad. I am thinking that the ViewDidLoad is running before it copies the variable from the 2nd into the textfield.
My main question is: should I be running my query statement in the ViewDidLoad or some please else to get the variable in the textfield. Basically, all I want to do is pull a record based on the value in the textfield upon returning from another UIViewController.
Thank You!
Technically, your viewDidLoad won't be called if your original view was never dealloced. The delegate methods that will be called are viewWillAppear: and viewDidAppear:.
You can pass the value from the second viewController back to the first one with a custom made delegate method. What you should keep in mind is that you should do the query with the NSString you pass back with the delegate method, and place it in the textField during viewWillAppear:.
Hope this helps!
viewDidLoad is only called when the view controller is loaded up from a nib. If you are switching back to one view controller from another, it won't be executed again. Try putting the code in viewWillAppear.
Must I always resignFirstResponder for a UITextView? Or, will this happen automatically when its view controller disappears?
I'm asking because I'm having an issue similar to iPhone Objective-C: Keyboard won't hide with resignFirstResponder, sometimes, where the keyboard stays up even when the nav controller pushes and pops other view controllers. The keyboard works, and when I hit done, it unfocuses the UITextView (i.e., the cursor disappears), but the keyboard stays up.
I never found out why this is happening, but maybe it's due to not doing resignFirstResponder before pushing another view controller, but I thought it was optional?
At a total guess, the UITextView has a reference to the view controller (as its delegate) but does not retain it. When you go to the next screen, the controller is dealloced and then the UITextView (which has perhaps been retained by something else) tries to call back to the dealloced controller and crashes. When you call resignFirstResponder, you reverse the order this happens, and therefore no crash.
The way round this to add a textView.delegate = nil call in your view controller's dealloc method - obviously put it before you release the text view.
The contract between a UITextView and it's delegate says that the delegate will send -resignFirstResponder when the text view is done editing. This informs the framework that the view is done editing, fires the events relating to that (willEndEditing and didEndEditing), and allows other parts of the responder hierarchy to react accordingly. Failing to do so might work, but it's not following the contract (that's all a protocol is) it agreed to.
I don't think you have to because the Xcode Sample UICatalog UITextField doesn't call resignFirstResponder before the TextViewController is popped.
The reason the keyboard got stuck for me is that I was having the same view controller present two view controllers modally at the same time, one after the other. UIKit didn't like that.
Calling resignFirstResponder makes sure that the text property contains the actual text shown in the control.
Depending on the state this is not always necessary, but if your controls have resigned first responder, you know that you're working with valid data.
I have created a tabBarNavigated Application. In second tab, I do something that works fine, but now I want to do something in the first Tab, so first I try to NSLog a string, but I get no reaction.
- (void)viewDidLoad
{
NSLog(#"Test");
}
If I add a label to the view, it will be displayed, but no reaction on my code.
if I start my app, i see this view, but i can't call any actions in this method, even if i change the tab, and go back to the first one, still no logs.
I try to NSlog in GehaltView
this is the mainWindow
viewWillAppear dosn't work :(
The -viewDidLoad method is only called when your view is loaded. This method will not be called again unless the view gets unloaded, in which case -viewDidUnload will be called. A view can be unloaded if there is a memory issue, but otherwise they generally stick around.
If you want to trigger an action that happens every time the view appears, then you can use the -viewWillAppear: method instead. This method is called every time the view re-appears. You can track when the view disappears with -viewWillDisappear, and watch the two get called as you toggle between the two tabs.
Note also that -viewDidLoad may get called before the view appears, but -viewWillAppear will only be called when the view actually appears (or moments before, as the will indicates).
EDIT: The code should read
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
NSLog(#"View Will Appear");
}
EDIT: This entire answer assumes that you have a subclass of UIViewController. It seems to me that you are by-passing using viewControllers, which in general is a bad idea.
I found the solution, in interface builder i have to add a custom class to the forst tab.